摘要:

COMPANY NEWS Paradigm Genetics/Bayer AG Paradigm Genetics Inc. (Paradigm) has delivered new assays for high-throughput screening to Bayer AG. The new assays are designed to identify novel classes of safe and effective herbicides. Bayer scientists will use the assays to screen their extensive compound collection for promising pro d uct leads. Paradigm will receive additional milestone payments during the course of the agreement and royalty payments on products discovered. Paradigm’s research collaboration with Bayer began in October 1998. Paradigm brings to the collaboration its expertise in gene function analysis and bioinformatics. Paradigm’s high-throughput analysis methodology is comprised of a series of proprietary analytical processes combined with a computerised knowledge base of plant and fungal gene function information.Paradigm has recently announced the discovery and genetic validation of its 100th novel herbicide target for highthroughput chemical screening. See www. paradigmgenetics.com/ Genoptera joint venture Exelixis Inc. announced that Genoptera LLC its joint venture with Bayer’s crop protection business group delivered several novel insecticide targets for assay development and screening to Bayer. Genoptera was formed in January 2000 to discover novel insecticides and nematicides. The joint venture is a continuation and expansion of the collaboration that Exelixis and Bayer initially established in April 1998 and expanded in June 1999. In addition to $80 M in committed research funding over the course of the eight-year joint venture the arrangement involves a $20 M up-front payment and performance-based milestone and royalty payments from Genoptera to Exelixis.Bayer has the exclusive right to commercialise insecticides based on techn o logy developed by Genoptera. See www. bayer-agro.com and www.exelixis.com/ Dow AgroSciences looks to acquisitions and alliances Dow AgroSciences Indianapolis IN currently ranked number 6 in agrochemicals is looking to acquisition and partnerships to keep up with the major players. The company recorded about $2.3 bn in agrochemical seeds and biotechnology Please send any contributions to the NEWS sections in Pesticide Outlook to Hamish Kidd The Royal Society of Chemistry Thomas Graham House Science Park Cambridge CB4 0WF.FAX +44 (0)1223 420247; email KIDDH@RSC.ORG. 2 Pest ic ide Outl ook – Fe b r u a r y 2001 This journal is © The Royal Society of Chemistry 2001 sales in 1999. So far Dow AgroSciences has maintained its market position through strong product sales rather than blockbuster mergers. It is supported by the full resources of parent company Dow Chemical the world’s second largest chemical producer with sales of $19 bn/y. Dow AgroSciences accepts that to avoid become a niche company it must keep pace with the larger players and have sales in the region of $3.5–4 bn. An ideal approach for Dow would be to partner with another significant player. Since Dow’s acquisition of Sentrachem South Africa in 1997 alliances have focused principally on glyphosate.In 4th quarter 1999 it established a joint venture with Finagro SpA-IpiCi for plant construction and production of glyphosate in Italy. Dow also has a multiyear glyphosate agreement with Monsanto under which it toll produces the herbicide has rights to Monsanto’s registration data and enables its US customers to apply Dow-branded glyphosate to Roundup Ready crops. In insecticides Dow Agro S c i e n ces has had significant success with spinosad. With its first year in the UK and Germany florasulam a new herbicide has proved to be a great success. Dow AgroSciences has recently agreed a 50:50 joint venture with Cheminova A/S called Pytech Chemicals to develop new pyrethroids.See www.dowagro. com/ Exelixis completes acquisition of Agritope Exelixis Inc announced the completion of its acquisition of Portland OR based Agritope an agricultural biotechnology company that develops improved plant products and provides technology for the agricultural industry. Agritope will be renamed Exelixis Plant Sciences Inc and will function as a wholly-owned subsidiary of Exelixis Inc. The acquisition provides Exelixis with expertise in higher plant model systems such as Micro-Tomato Arabidopsis and grasses as well as key intellectual property and extensive experience in plant biology. This proficiency combined with Exelixis’ superior programmes in bioinformatics genomics and simple plant model system genetics programmes creates an industry-leading plant genomics programme.The technology and intellectual property base of the newly formed Exelixis Plant Sciences will provide opportunities to establish additional funded partnerships with major companies in numerous areas with large market opportunities including plant traits industrial products biopetroleums and agricultural chemicals. In connection with the completion of the acquisition the stockholders of Agritope will receive about 1.7 M shares of Exelixis common stock in exchange for all of the outstanding shares of Agritope Series A preferred and common stock. Exelixis is a leading life sciences biotechnology company focused on product development through its expertise in comparative genomics and model system genetics.See www. exelixis.com/ Rohm and Haas and AgraQuest strategic partnership Rohm and Haas has signed a 3-year deal with AgraQuest to develop biopesticides based on naturally occurring microbes identified using AgraQuest technology. Over 13,000 microbes have been screened for possible use as pesticides. AgraQuest’s first commercial product the biofungicide Serenade (Bacillus subtilis strain QST 713) recently received EPA registration for use in grape nut and vegetable crops. See www. rohmhaas.com/ and www.agraquest.com/ Syngenta sells products to Makhteshim Syngenta is to sell two pesticide lines to Makhteshim-Agan Industries. Makhteshim will make an up-front payment of SFR 140 M for the grass herbicide propaquizafop and for the wheat and fruit insecticide taufluvalinate.Further payments may be required later depending on the products’ sales growth. Sale of the two products was a European Commission condition for approval of the Syngenta merger. See www.syngenta.com/ Syngenta Crop Protection announces transition from its diazinon business Syngenta Crop Protection USA (Syngenta) announced a 4-year phase out from its diazinon insecticide business. The company made the business decision to end its diazinon sales after a full analysis of the product’s financial performance. Although diazinon sales have remained strong the DOI 10.1039/b100792k margins on this product have continued to erode due to a very competitive marketplace.Diazinon has been marketed worldwide for more than 40 years. In the US it is sold mainly to control home lawn and garden insect pests and many agricultural pests. While other manufacturers will continue to sell diazinon for agricultural uses after 2004 Syngenta will phase the product out completely. See under Regulatory News in this issue and www.syngenta.com/ Snippets …Bayer is reported to have expressed an interest in taking over certain activities of Aventis CropScience which Aventis has indicated that it will spin off by the end of 2001. Bayer’s turnover in crop protection chemicals totalled EUR 2.2 bn in 1999 and is forecast to reach EUR 3 bn by 2004. …Bayer has commissioned a new $1.4 M herbicide production plant in Bangpoo Thailand.The plant will supply the SE Asian market with new herbicides. The new rice herbicide fentrazamide will be produced at the plant that has a capacity of 2000 tonnes/year. See www.agro.bayer.com/ …The Agricultural Ministry of Kazakhstan will spend more than 80% of funds budgeted for pesticides in 2001 on measures to combat locust. The measures require an investment of around DM 32 M and will target around 5 M hectares of agricultural land from March 2001 onwards. …A new herbicide for grass weeds oxaziclomefone has been announced by Aventis CropScience Japan and Zen-Noh Japan. Oxaziclomefone has been registered in Japan for use in herbicide mixtures for paddy rice and turf and has been developed jointly by Aventis Japan and Zen-Noh.It is expected that the new herbicide will strengthen Aventis Japan’s position in the Japanese rice market which is valued at about $1.175 bn. Oxaziclomefone is also under development in various other Asian countries including Vietnam Thailand Korea and China. See www.aventis.com/ …Microbio Ltd Cambridge UK has been acquired by Becker Underwood Inc Ames IO. The agreement includes the exclusive AGCHEM Forum Ad Reduce to fit Pes ti cide Out look – Fe b r u a ry 2001 COMPANY NEWS production and marketing rights for all MicroBio biofertilisers and biopesticides for the agricultural professional turf and glasshouse markets. Included in MicroBio’s product range is HiStick (rhizobium inoculant for legume crops) Nemasys (a nematode-based biopesticide for glasshouse nursery stock and speciality crops) and MBI 600 (a novel strain of Bacillus subtilis). See www.microbiogroup. com/ …UK company A H Marks has commissioned a new plant. The opening of the unit marks the start of a ten-year agreement under which Marks will produce phenoxy herbicides for BASF. See www.ahmarks. com/ …Bayer A G celebrated the topping-out ceremony in December 2000 for a new DM 220M multipurpose pesticides production facility at Dormagen. From 2002 production and process development throughout Germany will be brought together at Dormagen. See www.agro.bayer.com/ 3

ISSN:0956-1250    

DOI:10.1039/b100792k

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

REGULATORY NEWS Persistent Organic Pollutants (POPs) treaty finalised Diplomats from 122 countries finalised the text of a legally binding treaty at the INC-5 meeting in Johannesburg in December 2000. The treaty will require governments to minimise and eliminate an initial list of 12 toxic chemicals which include eight pesticides (aldrin chlordane DDT dieldrin endrin heptachlor mirex and toxaphene) two industrial chemicals (PCBs and hexachloro-benzene) and two unwanted by-products of combustion and industrial processes (dioxins and furans). The treaty sets out control measures covering the production import export disposal and use of POPs. Governments are to promote the best available technologies and practices for replacing existing POPs while preventing the development of new POPs.A POPs Review Committee will consider additional candidates for the POPs list on a regular basis to ensure that the treaty remains dynamic and responsive to new scientific findings. A financial “mechanism” will help developing countries and countries with economies in transition. “New and a d d i t i o n a l” funding and technical assistance will be provided. Most of the 12 chemicals are subject to an immediate ban. However a healthrelated exemption has been granted for DDT which is still needed in many countries to control malarial mosquitoes. This will permit governments to protect their citizens from malaria until they are able to replace DDT with chemical and non-chemical alternatives that are costeffective and environmentally friendly.The meeting was the fifth and final POPs negotiating session and was attended by some 600 participants. The treaty will be formally adopted and signed by ministers and other plenipotentiaries at a Diplomatic Conference in Stockholm on 22–23 May 2001. Governments must then ratify and when 50 have done so the treaty will enter into force; this process normally takes several years. For more information on the POPs negotiations see Pesticide Outlook 2000 11 123 and http://www.chem. unep.ch/pops/ 4 Swedish ban on BioAgri’s Cedomon removed Kemikalieinspektionen (KemI) Sweden has withdrawn its ban on BioAgri’s biological fungicidal seed dressing Cedomon. This product consists of the bacterium Pseudomonas chloraphis and is used to protect cereals.KemI imposed a temporary Pest ic ide Outl ook – Fe b r u a r y 2001 This journal is © The Royal Society of Chemistry 2001 sales ban on Cedomon in spring 2000 when it learned that the bacterium produced a metabolite that was a suspected carcinogen and requested further information from BioAgri. It was established that the metabolite was broken down rapidly and that the bacterium was unable to survive at human body temperature; furthermore it was not spread via plants. The agent has now been approved until February 2002 but it is required that every batch produced must be examined to check that the concentration of the metabolite 2,3-diepoxy-2,3-didehydrorhizoxin does not exceed 0.24 mg/l Cedomon.Provisional EU approval has been granted for Cedomon and at some point a decision will be made whether to place it in the Annex 1 list of products that can be used in all member states. See www.bioagri.se/ Own use parallel import approvals Own use parallel import approval is where in the UK individuals or groups of farmers may apply for and receive an approval for use and storage of a foreign pesticide/plant protection product if they can prove that it is identical to a product already approved in the UK. The product may not be advertised marketed or sold and may only be used by the individual or group who have been granted the approval. In order to make this system easier to use the UK’s Pesticides Safety Directorate will release a list of approvals granted showing the imported products and their equivalent UK product.A table lists existing own-use approvals and their identical products for example Allegro (BASF) Belgium (country of origin) identical to Landmark (BASF) UK product MAFF number M08889. Further information can be found in Pesticides Monitor Nov-Dec 2000 (11) 1–2 (Available from The Stationery Office PO Box 276 London SW8 5DT UK). UK pesticide tax Following the rejection of the agrochemical industry’s latest proposal for voluntary measures in the November 2000 pre-budget statement UK government plans to introduce a pesticide tax will be fought to the end. The industry’s proposal was intended to minimise the potential impact of agrochemicals but it was not considered adequate by the government.The government will introduce a £120 M/y tax in the second quarter of 2001 unless a revised package can be agreed. The UK’s Crop Protection Association (CPA) representing the agrochemical industry proposed voluntary measures to regulate pesticides which included training research into integrated crop management additional spray equipment further promotion of best practice and annual crop protection plans. This would have cost the industry £11.5 M/y. The CPA is convinced that any tax on pesticides would damage UK agriculture without any environmental benefits. The CPA will now work with farming groups to try to identify an alternative solution.The CPA does not believes that pesticide taxes are the most effective means of reducing pesticide use and it has put together an alternative plan to help regulate their use. A summary of the 24 revised proposals (February 2001) minimising the environmental impacts of crop protection chemicals can be downloaded from http://www.cropprotection. org.uk/. and a copy of the full version of the submission can be obtained by contacting Sue Thompson at the Crop Protection Association (Tel. 01733 349225 or e-mail sue.t@cropprotection.org.uk). Two pesticides added to Rotterdam Convention Two insecticides suspected of being carcinogenic (ethylene oxide and ethylene chloride) were added to the list of dangerous chemical products under international control by the 6 November 2000 meeting of experts from more than 100 countries charged with completing the Rotterdam Convention (formerly the PIC Procedure).The Convention was adopted in 1998 under the aegis of the United Nationals Environment Programme and the United Nations Food and Agriculture Organisation and sets out special procedures for the import of 22 pesticides and 5 industrial chemicals products. Countries have the right to refuse to allow imports of these substances and must be informed in advance about potential dangers to health and the environment. 73 countries have signed the convention but it has only been ratified by 11. It will not come into full force until it obtains 50% ratification.Both ethylene oxide and ethylene chloride are used as agricultural pesticides on stored foodstuffs; they are also used in making industrial chemical products. Only the agricultural use of these products (already banned in 20 countries) is covered by the Rotterdam Convention. For more information on the Rotterdam Convention see Pesticide Outlook and DOI 10.1039/ b100794g h t t p / / w w w. f a o . o rg / WA I C E N T / F a o I n f o / Agricult/AGP/AGPP/Pesticid/PIC/pichome. htm/ l l l Snippets l …The UK government is calling for agreement on national indicators of the impact of the use of pesticides on the environment. The five criteria which have been put forward are water quality area of cereal field margin under environmental management measurement of operator training levels on farm investigation of proportion of active agronomists who are on the BASIS professional register uptake of new technologies.Monitoring of any improvements would be better achieved if benchmark levels of these indicators could be established. l …Bayer is prepared to withdraw two thirds of its 60 agrochemicals from the market a decision which was made in the context of proposed new European environmental regulations. This will result in a small decrease in turnover and profits but an increase in income from the remaining products. The European Commission wants around 800 insecticidal formulations to be thoroughly reviewed. …a protest against the use of Gaucho Bayer’s insecticide imidacloprid has been held in France by beekeepers’ organisations.Since 1996 over 450,000 apiaries claim to have been affected by the insecticide and beekeepers are seeking a ban on the product. However Bayer claims that studies were partial and take no account of recent studies that illustrate the insecticide is harmless. …The US Environmental Protection Agency has revised its assessment of the pesticide malathion. It now says that the organophosphate does not pose risks to the public in drinking water food or through mosquito or cotton pest control. Some risks for agricultural workers have been identified. The agency is considering if organophosphates meet the stricter risk assessment standards of the Food Quality Protection Act.The EPA estimates that malathion usage is 16.7 M pounds/yr. …on 14 December 2000 the Dutch Second Chamber passed a motion by the Christen- Unie party that farmers and horticulturalists should pay a tax on pesticides. The motion had the support of PvdA The Pesticide Manual Ad to go here reduce to fit. Pes ti cide Out look – Fe b r u a ry 2001 REGULATORY NEWS GroenLinks SP and D66. It is hoped to use the money raised to stimulate the development and use of more environmentally friendly agents. …The European Commission is to withdraw its authorization for all pesticides containing the active ingredient tecnazene because of a insufficient safety data. The withdrawal will take around 6 months but member states can grant a period of grace of up to 20 months to allow for disposal and use of existing stocks. …The US EPA has reached an agreement with producers of diazinon on the phasing out of the insecticide in lawn and garden uses. The plans call for an end to sales of diazinon for use in the home by December 2002; and an end to lawn and garden use by December 2003. Certain agricultural uses will continue but current overall use of over 13 M lbs/y will fall 75%. Syngenta Crop Protection USA is to phase out all of its US diazinon insecticide business by 2004. …on 4 December 2000 the European Commission adopted a Directive amending Annex I of Directive 91/414/EEC on the marketing of plant protection products so as to include a further active substance lambda-cyhalothrin from 1 January 2002. 5

ISSN:0956-1250    

DOI:10.1039/b100794g

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

CONFERENCE REPORT PLANT DISEASE CONFERENCE IN FRANCE France from 6–8 December. The event was organised by AFPP (www.afpp.net) the French counterpart of the British Crop Protection Council. Over 600 delegates attended some 15% from abroad (24 countries). There were 130 presentations and posters as well as a trade exhibition with some 25 stands. Brian Hicks editor of the business newsletter Crop Protection Monthly reports on some key parts of the 6th International Conference on Plant Diseases (CIMA) which was held at the Vinci conference centre in Tours made quicker by adding fluorescent dye to the system socalled “TaqMan chemistry”. With the use of robotics and microtitre plates PCR diagnostics can be speeded up to take as little as two hours. Dr Hollomon identified a number of problems that still need to be resolved with diagnostic techniques such as linking them with fungicide rates spraying thresholds and economic decisions of whether to spray fungicides or not.One diagnostic technique not mentioned by Dr Hollomon but pointed out by Dr Phil Russell of Aventis CropScience is the human sense of smell which can be very helpful to farmers. It can be used to detect potato blight bunt and other diseases and some research has been done into the development of “artificial noses”. Diagnostics in crop production Dr Derek Hollomon of the department of agricultural sciences at the University of Bristol (UK) gave the introductory presentation on Modern Diagnostics in Crop Production. A French translation of his text also appeared in December’s edition of the French journal Phytoma.Dr Hollomon’s laboratory is actively involved in the detection of disease resistance. He argued that more precision is needed with crop inputs and that diagnostic tools were an important contributor giving both consumer and environmental benefits. Payment for the use of diagnostics could come from agrochemical companies to promote product sales from the advisory sector to improve advice given or directly by farmers themselves. Dr Hollomon reviewed the different technologies in agricultural diagnostics including imaging ELISA and PCR and their potential uses in optimising seed pesticide and fertiliser inputs. He commented that converting diagnostics into something practical still posed some real challenges.Immuno-assay techniques such as ELISA are not being developed much further. The focus is now on DNA-based approaches such as PCR which are usually much more sensitive allowing for earlier “pre-symptomatic” disease detection (2–3 days in the case of Septoria). Diagnostics are being regularly used in oilseed rape cereals bananas grass (especially on golf courses) grapes (for detecting Botrytis) and peas (for bacterial diseases). He cautioned that commercialising diagnostics is not easy. One US company backed by venture capital which pioneered turf grass disease diagnosis is no longer in business. Detection of Fusarium spp producing mycotoxins is now done regularly by PCR in the UK for about £30 per test.However to understand the problems better Dr Hollomon said that more of the biochemistry needs to be known in particular relating to the conditions under which mycotoxins are produced. PCR methods require the use and availability of suitable primers. Dr Hollomon’s laboratory and another in Bordeaux have developed specific primers to detect fungicide resistance to DMI fungicides triazoles and strobies. One example is the detection of point mutations conferring resistance to barley powdery mildew. PCR detection of resistance alleles can be Pest ic ide Outl ook – Fe b r u a r y 2001 This journal is © The Royal Society of Chemistry 2001 New products Seven new fungicides were presented in both poster and round table sessions. More details (post-Brighton) were given about trifloxystrobin picoxystrobin BAS 500F and famoxodone.Aspects were revealed of the unique mode of action of quinoxyfen which has been gaining sales in cases of known resistance problems. It is very rapid in its activity in both vines and cereals. French approval for trifloxystrobin is expected for the start of 2001 for cereals top-fruit and vines. In cereals it will be sold alone (as a 125 g/l formulation) and as a mixture containing 187.5 g/l trifloxystrobin and 80 g/l cyproconazole. Picoxystrobin is being developed AFPP AFPP (Association Française de Protection des Plantes) has a secretariat of three staff based in Paris under the director Philippe Printz. The origins of AFPP date back to 1953 from which ANPP (Association Nationale de Protection des Plantes) was formed in 1984.There was a slight change in the association’s name in January 2000 from ANPP to AFPP to better reflect the association’s role in plant protection in France and the French-speaking world. AFPP has just established a new commission on “alternative 6 methods of control” which has five working groups under its auspices. These cover micro-organisms macro-organisms natural products mechanical methods and prophylaxis respectively. Next year’s AFPP conference (“COLUMA”) will be devoted to the theme of weed control and will be held in Toulouse from 5–7 December 2001 under the presidency of Jean-Louis Pasquereau a well-known technical specialist at the co-operative Agri 18 (part of Épis-Centre) Bourges.DOI 10. 1 0 3 9 / b 1 0 0 7 9 5 p in France for use in cereals alone and as a mixture (125 g/l picoxystrobin + 25 g/l hexaconazole). Zoxamide is a new benzamide fungicide from Rohm and Haas which inhibits cellular division. The first microgranule formulations for sale in France will be for potatoes (8.33% zoxamide + 66.7% mancozeb) and for vines (6.25% zoxamide + 70% mancozeb). Fenamidone developed by Aventis is an optically active isomer. It will only be sold in mixtures in France in vines at a dose rate of 75–133 g ai/ha with fosetyl-al cymoxanil copper hydroxide or folpet. For potatoes a formulation with 10% fenamidone and 50% mancozeb will be commercialised. The unique mode of action of the Monsanto seed treatment for take-all in wheat silthiopham (Latitude) has recently been elucidated.It disrupts the energy process outside the mitochondrion. Goëmar Laboratories St Malo France presented details of a natural seaweed-derived product laminarin which enhances cereal disease resistance. Roundtable on food security There was some animated discussion in the conference “round table” on food security and the response of the sector to the demands of distributors and consumers. French consumers have become “sensitised” with recent revelations that “mad cow disease” is a real problem and that the effects have been underestimated. Beef sales have been plummeting in France as a consequence and strict feed controls will now be enforced. Gérard Benoist du Sablon from the French consumer group Organisation Générale des Consommateurs (http:// perso.wanadoo.fr/orgeco) gave delegates a foretaste of the results of a consumer survey conducted by the Ipsos group.French consumers broadly feel that there is “more choice and more control but less taste in food today”. Some 75% of those surveyed said that risks were small due to frequent checks. He personally prefers “to view the glass as half-full rather than half-empty” and does not want to look at his plate and examine “what is a GMO and what is not”. Mr du Sablon said that big brands still have a positive image. Consumers are eating much more varied food but want to know more about the controls applied and its history. They are in “permanent crisis and psychosis” because of the risks.A representative of a tomato and cucumber growers’ group (accounting for 10% of the French market) explained its national quality charter and focus on biological and ADDITIONS AND CORRECTIONS Promoting international collaboration for potato late blight disease management K.V. Raman Niklaus J. Grunwald and William E. Fry Pesticide Outlook October 2000 11(5) 81–185 (DOI 1039/b008008j) The authors would like to point out that on page 182 under the section “The need for global research to control late blight” the sentence “However Eastern Europe and Mexico are not yet involved in these initiatives” should be replaced by the following “Both Eastern Europe and Mexico are currently participating in GILB. GILB supported the first meeting of Eastern Europe’s linkage group in 2000 and also had Eastern Europe represented at the Global Conference on Late Blight in Quito Ecuador in 1999.In the same way Mexico was represented in GILB organized global meetings. National program staff from Mexico have been members of the Latin American and Carribbean Linkage Group.” Evolving disease control Phytopathogenic fungi are estimated to account for some 20% of crop losses today. Their adaptability and diversity makes it a continuous struggle. One speaker said that it now typically costs some FFr 2,000 million to develop a new fungicide and that only five or so firms could now afford these development costs. At the end of the conference Nadine Cavelier (INRA) reflected on how disease control should evolve.She said that better knowledge of fungi and the epidemiology of diseases was essential adding that “common sense” was sometimes lacking in the approaches followed. She argued that a lot of work was required at the “prescription” and education levels and that it was important that what had been presented at the conference reached “those in the field”. CONFERENCE REPORT integrated crop protection. He commented that predators could sometimes cause problems and that traceability is a key consideration. The group set up a quality assurance scheme at the end of 1997. Export requirements are strict with residues an important aspect. Only specified products are permitted and this is controlled by an outside organisation from seed to final product.On the taste issue he said that tomatoes and cucumbers must be at room temperature for best results and commented that “if you want to eat well you have to consider the price”. Dr Hervé Lafforgue a toxicologist at the food company Danone commented that “you cannot separate good agricultural practice (GAP) from environmental protection and quality”. He added that too much focus is often put by farmers on the products used rather than “the whole picture” which should take into account aspects such as whether a sprayer was working properly. Mr Lafforgue said that pesticide residue analysis was becoming very effective but that it should be a toxicologist who judges it and the analyst must not fix the norms a comment met with much applause from the conference floor. Several delegates stressed the need to develop a single official “IPM logo” as a reference standard in France for food marketing purposes rather than having a plethora of standa rds. Appreciable premiums can be obtained for assured produce commented one delegate as evidenced by “IPM flour” sold at the supermarket chain Carrefour. 7 Pes ti cide Out look – Fe b r u a ry 2001

ISSN:0956-1250    

DOI:10.1039/b100795p

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

R&D NEWS Two new strobilurins BASF is moving toward the launch of a new fungicidal active ingredient of the strobilurin class code named F 500. Details were presented by BASF scientists at the British Crop Protection Conference in Brighton UK. Found to control the major plant pathogens from all classes of fungi F 500 has a broad range of efficacy against many diseases in many crops including cereals grapes vegetables and fruits. It is claimed to set a new standard for Septoria tritici control. Zeneca Crop Protection UK also made a high profile launch for Syngenta’s picoxystrobin strobilurin fungicide claiming faster uptake systemic activity and greater curative control of Septoria tritici net blotch and rhynchosporium than existing strobilurins (see page 38).Parkinson’s pesticide connection reinforced Researchers at Emory University say new studies support the notion that chronic exposure to pesticides could contribute to the onset of Parkinson’s disease although observers advise against reaching sweeping conclusions from the studies of rotenone in rats. These studies were meant to test scientific concepts to see if a better animal model for Parkinson’s disease could be produced. Low doses of rotenone in rats produced Parkinson’s symptoms accompanied by Lewy bodies (a characteristic of Parkinson’s) and a generalised deficiency of Complex 1 in the rats. It is acknowledged however that the study does not furnish enough evidence that rotenone or any other specific pesticide is a culprit in Parkinson’s disease.The results justify further epidemiological studies on the effects of pesticides. Other studies by the University of Rochester found a link between Parkinson’s and exposure to a combination of paraquat and maneb. For more information see Nature Neuroscience 2000 3(12) 1301. 8 Volatiles for defence Maize releases a cocktail of indole and terpenoid compounds when attacked by the beet armyworm (Spodoptera exigua). These compounds attract a parasitic wasp which deposits its eggs in the caterpillar; the wasp larvae then devour the caterpillar. Two groups have identified the genes involved in the production of these volatile defence chemicals [Proceedings of the National Academy of Sciences 2000 97( 2 6 ) 14801– Pest ic ide Outl ook – Fe b r u a r y 2001 This journal is © The Royal Society of Chemistry 2001 14812].Frey et al. (pp. 14801–14816) identified the gene IgI involved in the synthesis of indole while Binzhang Shen et al. (pp. 14817–14812) identified the gene stc1 required for maize to make a terpenoid. Termite control Heumann Greenhouse & Laboratory Metairie LA and the Louisiana State University Agricultural Center are cooperating in the development of vetiver as a “miracle insecticide”. Vetiver is a fragrant grass containing over 300 chemical compounds one of which nookatone is repellent to Formosan subterranean termites. The partners hold a preliminary patent on the compound. As a wood treatment nookatone prevented the termites moving on the treated surface and in the soil it stopped tunnelling activity.As a semi-volatile material it would need to be applied every few months. Recent tests have shown that the mixture of oils from the plant may be more effective than nookatone on its own. For more information see www.vetiver.com/ Methyl bromide …paddy fields release halides Paddy fields release methyl halides as a metabolic by-product of methane generation. Measurements by GC-MS of methyl chloride methyl bromide and methyl iodide released from growing rice plants show that more methyl iodide is released than either of the other two halides indicating a possible preferential take-up of iodide during active biological processes.Extrapolation suggests that global rice production might be responsible for 1–4% of atmospheric methyl bromide and methyl iodide respectively. …naturally occurring soil micro-organisms as alternatives A research programme into methyl bromide substitutes at the ARS Horticultural Research Laboratory in Fort Pierce FL found that adding the soil micro-organisms Paenobacillus macerans a n d Bacillus amylo-liquefaciens to a transplant mix stimulated plant growth. A combination of the organisms were added to the transplant mix BioYield 213. This gave yields similar to those obtained using the soil fumigant methyl bromide. …propargyl bromide as alternative Propargyl bromide (3-bromo-1-propyne) is active against a broad range of soilinhabiting pests and may prove to be the best of the methyl bromide alternative options.However this is still a long way to go before a pesticide registration application is made to commercialise propargyl bromide. For more information on methyl bromide alternatives see http://www.epa.gov/ docs/ozone/mbr/mbrqa.html …14 consumer health and environmental organisations from around the world have called on the government of the People’s Republic of China to end the rapidly increasing production and consumption of methyl bromide. China has become the leading producer and consumer of methyl bromide in the developing world producing 2320 tons in 1998 with production expected to rise to over 4000 tons in 2002. Snippets …the glassy winged sharpshooter is a major problem for Californian viticulture (Pesticide Outlook 2000 11(6) 218).A researcher at the University of California Riverside has identified 5 pesticides with 100% efficacy against the insect Admire (the unregistered acetamiprid) Marathon (malathion) Merit (imidacloprid) Mesurol (methiocarb) and Tame (fenpropathrin). …the US Agricultural Research Service (ARS) is working with Trécé Inc. who have a licence for a patented gluten-based syrup which shields insecticides against the effects of UV light. The ARS says that treatments which use the syrup with pyrethroids carbamates and organophosphates at 10% dose levels worked better than conventional sprays. The new technology may also slow down the development of insecticide resistance in corn rootworms. For more information see www.trece.com/ …following £1.5 M of research in the UK it has been concluded that strobilurin resistance to wheat mildew is now widespread. …research by the USDA ARS has shown that treating apple trees with processed kaolin produces larger fruit. This may be due to reflective properties of the material reducing leaf temperature and heat stress. Other US studies show that kaolin applications reduce insect attack. It is hoped that kaolin film can be used to reduce mildew infection. DOI 10.1039/b100796n

ISSN:0956-1250    

DOI:10.1039/b100796n

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

Plant genomes sequenced …Arabidopsis The first complete sequence of a plant genome has been published – namely the sequence of the genetic model plant Arabidopsis thaliana (Nature 2000 408 796–815). Arabidopsis was chosen as a genetic model because its genome is one of the smallest and seemingly one of the simplest among flowering plants. Other plant genomes will follow [e.g. rice (see below) and maize] and eventually researchers will be able to identify important genes in crop plants for breeding or genetic engineering programmes. For more information see h t t p / / w w w. n a t u re . c o m / g e n o m i c s / p a p e r s / a_thaliana.html …rice Syngenta and Myriad Genetics announced in late January 2001 that they had finished the sequencing of the genetic code for rice – the first crop plant to be completed.The two companies had beaten a publicly funded group of scientists working in Japan China Korea Europe and the USA (see T Sasaki Pesticide Outlook 1999 10(3) 114). Action Aid a hunger charity was alarmed by the announcement as there are currently 239 patents granted on the crop which is the staple diet of much of the world’s poorest people. Syngenta says that it will sell data to seed and other companies and make the information available to research scientists through contracts but that it will not charge those working with subsistence farmers. The companies do not plan to patent the genes but they will cover their uses. For more information see http://www.myriad.com/ or http://www.syngenta.com/ Gametocides in hybrid production Gametocides are chemicals used to sterilise the pollen of the mother line in the production of hybrid crops.Only two are approved in the EU Genesis from Monsanto and Crosoir from Hybrinova. In northern Europe their use is only permitted in France. Monsanto now intends to sell Genesis and its interests in present wheat hybrids ostensibly because of indifferent profitability of the enterprise. However the product is on conditional approval until 2003 has high application rates and soil DOI 10.1039/b100797l BIOTECHNOLOGY NEWS residue problems. Monsanto intends to stay in hybrid wheat production but perhaps through gene technology. Hybrinova’s problems are different; Crosoir is environmentally benign but less effective as a steriliser.Field trials in the UK with current wheat hybrids show gametocides to be unsuitable for the climate For more information see www.monsanto.com and www.hybrinova.com Aventis halts research on GM sugar beet because of crosspollination Aventis has stopped research on a genetically modified glufosinate-resistant sugar beet after discovering that some plants had also developed resistance to glyphosate through accidental cross pollination with another sugar beet crop. This is the first time in Europe that involuntary crosspollination has occurred between two different GM crops. The glufosinatetolerant sugar beet was developed for Aventis by KWS Germany.The EU’s standing committee for seed and propagation material is holding discussions on how much cross-pollination should be allowed from approved and non-approved GM seed varieties. The levels currently being considered are 0.5% for approved GM varieties and zero amounts of nonapproved seeds. If no degree of mixing is permitted then crops will have to be separated by unprecedented distances which according to Novartis Seeds Sweden would be impractical and very expensive. For more information see www.aventis.com Transgenic corn contamination saga The reverberations from the discovery some weeks ago of unapproved genetically modified corn in taco shells continue. The companies involved are taking action to prevent any similar occurrence and federal agencies are intensifying efforts to make sure the corn does not contaminate any further human food products.The US Department of Agriculture is to buy almost all the corn grown this year from Aventis CropScience’s StarLink seed and sell it to animal feedlots or ethanol makers. The corn is approved for animal feed but not for human consumption because there are Pes ti cide Out look – Fe b r u a ry 2001 This journal is © The Royal Society of Chemistry 2001 concerns it may cause allergic reactions. It is engineered with a gene to produce a Btendotoxin (Cry9C). The protein is stable to heat and digestion – two of the characteristics of food allergens. The USDA’s repurchase of the corn is aimed at preventing more StarLink entering the human food supply.It is also seeks to reassure foreign grain customers like Japan that shipments will not contain any StarLink. The FDA is testing more processed food for the presence of StarLink. California high court takes up Bt dispute The California Supreme Court is to hear an appeal filed by Dow AgroSciences subsidiary Mycogen in a dispute over the licensing of Bacillus thuringiensis genes. The dispute relates to a 1989 technology arrangement between Monsanto and Lubrizol Genetics which Mycogen acquired in 1992. Mycogen sued after Monsanto delayed Mycogen’s access to the genes in the agreement for 4 years. A California jury awarded Mycogen damages of $175 M in 1998 but an appeals court overturned the verdict against Monsanto.Mycogen then filed to have the damage award reinstated. Snippets …France’s highest administrative court has upheld the French government’s approval in 1998 for the sale and planting of three types of GM corn containing Syngenta’s Novartis Event 176. …Monsanto says it has developed genetically modified potatoes containing an antifungal gene present in alfalfa. Researchers isolated an alfalfa peptide sequence known as defensin that inhibits the growth of a key potato fungal pathogen. The company says defensin genes have potential for fungal control in commercial crops. …Demegen has been awarded a US patent for a method of modifying plants to produce lytic peptides. Crops producing these peptides show resistance to gram-negative bacteria as well as fungi causing a number of foliar and crown diseases. The technology is likely to benefit US farmers whose crops are affected by citrus canker Pierce’s disease and late blight. See www.demegen. com. 9

ISSN:0956-1250    

DOI:10.1039/b100797l

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

SAFENERS 10 HERBICIDE SAFENERS – COMMERCIAL PRODUCTS AND TOOLS FOR AGROCHEMICAL RESEARCH What is a herbicide safener? Herbicide safeners selectively protect crop plants from herbicide damage without reducing activity in target weed species. They are used commercially to improve herbicide selectivity between crop and weed species and can be applied either as a mixture with the herbicide or as a seed-treatment to the crop seed prior to sowing. This phenomenon is illustrated in Figure 1 which shows the response of maize plants to applications of the imidazolinone herbicide AC 263222 (Cadre). Those plants also treated with a seed-dressing of the herbicide safener naphthalic anhydride (NA) prior to herbicide application suffered little damage compared to those plants grown from untreated seed.Joanna Davies from IACR-Long Ashton Research Station in the UK discusses a group of chemicals which complement herbicides protected wheat from injury caused by the herbicide barban. However these interactions could not be exploited commercially as foliar sprays also protected target weed species while treatment of wheat seed with 2,4-D damaged the crop. Despite this initial set-back the potential significance of these interactions was recognized by Hoffman and a screening programme was set up to identify compounds with safener activity. This produced the first commercial herbicide safener 1,8-naphthalic anhydride (NA) which was patented by the Gulf Oil Company in 1971 for use as a seed-treatment to protect maize from injury by thiocarbamate herbicides.However Stauffer Chemical Company who marketed the thiocarbamates subsequently patented their own safener dichlormid. Unlike NA dichlormid with its superior selectivity could be formulated with the herbicide thus reducing application costs. This undermined the commercial value of NA which despite being active in a number of species and against a diverse selection of herbicides was withdrawn from the market (Hatzios 1983). Nevertheless the discovery of NA initiated intensive industrial research which over the last 30 years has led to the discovery of the oxime ether safeners namely cyometrinil oxabetrinil and fluxofenim by Ciba-Geigy (now Syngenta) and the 2,4-disubstituted thiazole carboxylates such as flurazole by Monsanto.The majority of these early compounds were active in cereal crops namely maize sorghum and rice while protection was only provided against preemergence applications of herbicides representing a narrow spectrum of chemistries and modes of action. However trends towards post-emergence herbicide treatments and the use of high activity herbicide molecules has led to the development of safeners to protect winter cereals against postemergence herbicides. Safener activity is now widely reported against many herbicides classes including aryloxyphenoxypropionate sulfonylurea imidazolinone cyclohexanedione and isoxazolidinone herbicides. Those safeners that have been used commercially are listed in Table 1. An accidental discovery The phenomenon of herbicide safening was discovered by Otto Hoffman in 1947 following the accidental exposure of tomato plants to vapour of the herbicide 2,4-D.Although previously treated with another herbicide 2,4,6-T plants curiously did not develop any herbicide symptoms. Further experiments showed that foliar treatment with 2,4-D also Figure 1. Protection of maize from AC 263222 injury by seed-treatment with naphthalic anhydride (NA). Pest ic ide Outlook – Fe b r u a r y 2001 This journal is © The Royal Society of Chemistry 2001 Safeners enable the use of environmentally-safe herbicides Safeners have many potential uses. Their major role enables the development of molecules with favourable environmental toxicology whose use would otherwise be limited by poor selectivity.To DOI 10.1039/ b100799h SAFENERS Table 1. Herbicide safeners available as commercial products. Pes ti cide Out look – Fe b r u a ry 2001 1 1 SAFENERS a lesser extent they are used to extend the use patterns of currently available herbicides. Other potential uses include protection of crops from damaging levels of pesticide residues to allow greater flexibility in the choice of crops grown in rotation and the use of herbicides under adverse environmental conditions where crop damage is likely to occur. In addition safeners can be used to address difficult weed problems which for technical and economic reasons are unlikely to be solved by the development of conventional selective herbicides.For example herbicide safeners could be used to facilitate the control of weeds in botanically-related crops or provide weed control options for minor crops which due to their small market value are not generally targeted for the development of new products. The commercial success of safeners is clearly reflected in the number of herbicide-safener products now on the market. However possibly their most important application lies in their use as powerful research tools with which to identify and manipulate the biochemical and physiological mechanisms controlling herbicide selectivity. It is for this reason that considerable research has been devoted to the study of safener mode of action. How do safeners work? Safeners work by reducing the ability of herbicides to reach and inhibit their target sites.Theoretically safeners could do this by interacting directly with the biochemical targets or receptor proteins of herbicides in crop plants. Alternatively they could reduce the amount of herbicide reaching this target in an active form either by reducing herbicide uptake or translocation or increasing the degradation of herbicides to less active or immobile metabolites. In reality safeners have been found to affect all of these processes and the elucidation of their primary mode of action has been a long process. The ability of safeners to prevent the detrimental effects of herbicides originally led to suggestions that safeners interact with those biochemical processes or target proteins whose activity would normally be inhibited by the herbicide.The structural similarity of several herbicide-safener combinations led to development of the competitive antagonist hypothesis whereby safeners are believed to compete with herbicide molecules for binding sites on target proteins. Recent comparisons of the 3D similarity between 28 safener and 20 herbicide molecules suggest that structural similarity between herbicides and safeners could provide a useful guide in the design of new safeners (Bordas et al. 2000). However where isolation of known herbicide receptors has been possible safeners have not directly influenced herbicide interactions with these sites. Instead safeners have been found to elevate levels of herbicide target enzymes and in some cases reduce the susceptibility of these enzymes to herbicide inhibition.For example levels of acetolactate synthase an enzyme involved in branched chain amino acid biosynthesis and the target of sulfonylurea and imidazolinone herbicides were not only elevated in maize plants treated with NA but were also less sensitive to inhibition by the sulfonylurea herbicide metsulfuron-methyl. Generally these studies have produced inconsistent results and have Pest ic ide Outlook – Fe b r u a r y 2001 12 failed to explain how a single safener such as NA can prevent injury from several herbicides which act at different target sites. Safeners could act by reducing herbicide uptake or translocation to sensitive tissue within the crop plant.However studies into the effects of safeners on these processes have produced a series of contradictory results with the majority suggesting that uptake is unaffected or actually enhanced by safener treatments. Where reductions in uptake have been seen they are usually considered a consequence of safener interactions with other processes. For example reductions in the uptake of the herbicide metolachlor seen following treatment with the safener cyometrinil can be attributed to a decrease in transpiration rate. This reflects the ability of cyometrinil to prevent the inhibition of epicuticular wax formation associated with metolachlor treatment. Further evidence dismissing the relevance of effects on uptake and translocation comes from the fact that in some cases safeners work even when applied after the herbicide.Under these circumstances safeners cannot interfere with herbicide uptake processes (Davies and Caseley 1999). Safeners promote herbicide metabolism in crop plants The susceptibility of a plant species to herbicide damage is often correlated with its ability to degrade the herbicide to less active or immobile metabolites. Most plant species detoxify herbicide molecules in three phases. Detoxification begins with oxidation of the parent molecule during Phase I followed by conjugation with natural substrates such as glucose amino acids or more commonly glutathione during Phase II. In some cases parent molecules bypass Phase I and enter Phase II directly.Although these reactions usually reduce the phytotoxicity and mobility of the herbicide Phase I metabolism is required for the activation of some herbicides such as fenoxaprop-ethyl. In this case the parent compond is de-ethylated during Phase I to produce the active compound fenoxaprop (Figure 2). During Phase III Phase II metabolites may undergo further conjugation to produce insoluble residues which are sequestered in vacuoles or bound in lignin biopolymers. Alternatively Phase II conjugates can be directly sequestered in the vacuole by the activity of glutathione or glucoside-conjugate pumps located in the vacuolar membrane (Cole 1994). The majority of oxidative Phase I reactions are catalyzed by cytochrome P450-dependent mono-oxygenases.These enzymes are haemoproteins associated with the smooth endoplasmic reticulum and are characterized by their ability to bind carbon monoxide producing an absorption maximum at 450 nm. Over 50 different systems are believed to exist in plants including biosynthetic systems involved in synthesis of natural substrates such as sterol terpene isoflavonoid gibberellin abscisic acid cytokinin and lignins as well as detoxification systems involved in the metabolism of herbicides. This class of enzymes has been demonstrated to be responsible for the degradation of the herbicides monuron chlorotoluron metolachlor alachlor bentazone chlorotoluron 2,4-D diclofop flumetsulam primisulfuron prosulfuron and triasulfuron (Barrett 1995; Schuler 1996). (1) Phase I – de-ethylation (2) Phase II – ether cleavage; glutathione conjugation (3) Phase II – cysteine conjugation (4) Phase II – glucose conjugation Figure 2.Metabolism of fenoxaprop-ethyl in higher plants. Several herbicide safeners increase crop tolerance to herbicides known to undergo oxidation suggesting that safeners could work by increasing the activity of the cytochrome P450 enzymes. At least 10 safeners have been shown to increase the oxidative metabolism of several mainly sulfonylurea and imidazolinone herbicides in several crop species including maize sorghum and rice. In many cases this increased degradation has been attributed to increases in the activity of enzymes with the characteristics of cytochrome P450 mono-oxygenases.When incubated with herbicide in the presence of NADPH and molecular oxygen membrane fractions extracted from safener-treated plants generate oxidative metabolites faster than membranes extracted from untreated plants. In some cases safeners cause up to 30-fold increases in the amounts of oxidative metabolites produced in vitro. Furthermore metabolite production can be inhibited by the addition of carbon monoxide (CO) or compounds such as 1-aminobenzotriazole (ABT) piperonyl butoxide and tetcyclacis which are known to inhibit P450 activities. These observations strongly suggest that such degradation is catalysed by cytochrome P450-dependent systems and that safeners work by promoting the activity of these systems (Davies and Caseley 1999). During Phase II metabolism conjugation of herbicides or their Phase I metabolites with glutathione is catalyzed by glutathione S-transferases (GST).In 1997 35 genes encoding GST enzymes were reported to have been identified from 13 plant species and seven of these were known to be involved in herbicide metabolism in maize (Droog 1997). Alternatively some herbicides undergo conjugation with glucose during Phase II. These reactions are usually catalyzed by glucosyl transferase enzymes (Cole 1994). SAFENERS Herbicide safeners also enhance crop tolerance to several chloroacetanilide and thiocarbamate herbicides which undergo glutathione conjugation during Phase II. At least 12 safeners have been shown to increase rates of glutathione-conjugation in several crop species Many of these reports are accompanied by observations of safener-induced promotion of glutathione levels in the crop plant.Safeners known to promote glutathione content include BAS145138 benoxacor dichlormid flurazole fenclorim MG191 and AD67. In some cases increases can be attributed to the increased activity of enzymes involved in glutathione biosynthesis. However safener activity is not always accompanied by elevated glutathione levels and efficacy is often better correlated with increases in the activity of GST enzymes. At least 12 safeners have been demonstrated to enhance GST activities in maize rice sorghum or wheat (Davies and Caseley 1999; Farago et al. 1994). In addition to enhancing glutathioneconjugation safeners are also reported to enhance the conjugation of oxidative metabolites with glucoside and promote the activity of vacuolarmembrane pumps responsible for the sequestration of metabolite-conjugates in the vacuole.In particular the safener cloquintocet-mexyl is reported to enhance the glucosylation of the herbicide clodinafop in wheat. This effect may result from promotion of UDP-glucosyl transferase activities or the increased availability of glucose due to enhanced synthesis (Kreuz et al. 1991). Furthermore treatment of barley with the safener cloquitocet-mexyl not only accelerates GST activity but has also been reported to enhance the activity of a vacuolar transporter for glutathione- and glucoside-conjugates (Gaillard et al.1994). The future for safeners Thus herbicide safeners have been shown to work by promoting the activity of enzymes responsible for Phase I and II metabolism and the membrane components responsible for compartmentation of the resulting metabolites. While safeners undoubtedly offer new solutions to the problems of herbicide selectivity there are still two major challenges concerning their activity. Firstly the failure of safeners to protect dicotyledonous crops remains a mystery. Safener activity has been observed in broad-leaf crops including potatoes soybeans and oilseed rape but these interactions have not resulted in the development of a commercial product. There is evidence to suggest that inducible metabolic activities responsible for safener activity in monocotyledons are also present in dicotyledonous crops.For example NA-inducible cytochrome P450 and safener-inducible GSTs have been reported in mung bean (Vigna radiata L.) and pea (Pisum sativum L.) respectively. (Edwards 1996; Moreland et al. 1995). Secondly the molecular pathway leading from recognition of safener presence to enhanced enzyme expression remains unknown. Safeners are believed to regulate gene expression 1 3 Pes ti cide Out look – Fe b r u a ry 2001 SAFENERS and have been demonstrated to increase levels of messenger RNA encoding GSTs responsible for herbicide conjugation in maize (Wiegand et al. 1986; Jepson et al. 1994). It is assumed that safeners modulate the activity of transcription factors that interact with regulatory elements within the promoter region of those genes encoding metabolic enzymes.However evidence for the interaction of safeners with such regulatory mechanisms has not been forthcoming. Tools for research Perhaps the most powerful application for herbicide safeners lies in their use as research tools with which to identify the biochemical processes determining herbicide selectivity. Characterization of biochemical dichotomies between target and non-target plant species is essential if these are to be exploited in the development of new environmentally-safe selective weed control strategies. The identification of safenerresponsive enzymes and genes will greatly assist this process and will inevitably provide biochemical and molecular tools with wide-ranging applications.The most obvious application of this information is in the development of genetically-modified herbicide-resistant crops with enhanced capacities for herbicide metabolism. This possibility has already been demonstrated in tobacco where introduction of a cytochrome P450 gene isolated from soybean gave resistance to the herbicide linuron (Ohkawa et al. 1999; Werck-Reichhart et al. 2000). However safenerresponsive genes also have a second less obvious role. To date the majority of genetically-modified resistant varieties have been produced by transformation with DNA comprising the “gene of interest” and a promoter region to which RNA polymerase must bind to initiate gene transcription. The use of constitutive promoters such as 35S from cauliflower mosaic virus (35S CaMV) results in expression of the gene in all tissue types throughout plant development.However combination of the gene of interest with a promoter region that is responsive to a specific stimulus produces an inducible gene expression system or gene switch which enables temporal spatial and quantitative regulation of gene expression . For example by using promoters derived from safenerresponsive genes gene expression can be switched on by treatment with the safener. This has been demonstrated by De Veylder et al. (1997) who introduced a b-glucuronidase (gus) reporter gene under the control of a promoter which responds to treatment with benzenesulfonamide safeners i n t o Arabidopsis.Plants treated with these safeners expressed the gene while untreated plants did not. Such systems have both commercial and academic uses allowing the regulation of resistance genes in the production of pesticide-resistant crops or the regulation of other genes of interest in the study of physiological and biochemical processes (Jepson et al. 1998). The isolation of safener-responsive enzymes and genes will also generate probes or biomarkers which could be used as tools in their own right. For example the availability of antibodies for specific enzymes known to be responsible for herbicide resistance could lead to the development of in vitro screens to identify potential safeners by testing their ability to induce critical activities or genes in Pesti c ide Outlook – Fe b r u a r y 2001 14 crop plants.Such probes could also be used in the development of field testing methods for the early detection of herbicide resistance problems in weeds. For example increases in GST levels as measured by ELISA could be used as an indicator of herbicide resistance in weed species. This approach is already used for environmental monitoring where the presence of pollutants particularly pesticides in complex water or effluent samples can be detected by the ability of a sample to induce a response such as enhanced cytochrome P450 activity in fish (Aas et al. 2000). Conclusion It is now widely accepted that herbicide safeners improve crop tolerance to herbicides by regulating the expression of genes involved in herbicide metabolism.With this mode of action safeners provide a relatively inexpensive and flexible method of improving herbicide selectivity without incurring the ecological risks perceived to be associated with geneticallymodified varieties. In commercial terms they will undoubtedly continue to provide new solutions to many weed control problems. In research terms their ability to modulate the metabolic pathways controlling herbicide selectivity makes them powerful tools with numerous applications. In particular the continued development of environmentally-safe crop p rotection products is dependent on fundamental knowledge of the differences in herbicide metabolism between target and non-target plants. Herbicide safeners with their unique mode of action are vital tools in the aquisition of this knowledge.References Aas E.; Baussant T.; Balk L.; Liewenborg B.; Andersen O. K. (2000). PAH metabolites in bile cytochrome P4501A and DNA adducts as environmental risk parameters for chronic oil exposure a laboratory experiment with Atlantic cod. Aquatic Toxicology 51(2) 241–258. Barrett M. (1995). Metabolism of herbicides by cytochrome P450 in corn. Drug Metabolism and Drug Interactions 12(3-4) 299–315. Bordas B.; Komives T.; Szanto Z.; Lopata A. (2000). Comparative three-dimensional quantitative structure-activity relationship study of safeners and herbicides. Journal of Agricultural and Food Chemistry 48 926–931. Cole D. J. (1994). Detoxification and activation of agrochemicals in plants.Pesticide Science 42 209–222. Davies J.; Caseley J. C. (1999). Herbicide safeners a review. Pesticide Science 55 1043–1058. DeVeylder L.; VanMontagu M.; Inze D. (1997). Herbicide safener-inducible gene expression in Arabidopsis thaliana. Plant and Cell Physiology 38(5) 568–577. Droog F. (1997). Plant glutathione S-transferases a tale of theta and tau. Journal of Plant Growth Regulation 16(2) 95–107. Edwards R. (1996). Characterization of glutathione transferases and glutathione peroxidases in pea (Pisum sativum). Physiologia Plantarum 98 594–604. Farago S.; Brunold C.; Kreuz K. (1994). Herbicide safeners and glutathione metabolism. Physiologia Plantarum 91 537–542. Gaillard C.; Dufaud A.; Tommasini R.; Kreuz K.; Amrhein N.; Martinoia E.(1994). A herbicide antidote (safener) induces the activity of both the herbicide detoxifying enzyme and of a vacuolar transporter for the detoxified herbicide. FEBS Letters 352 219–221. Hatzios K. K. (1983). Herbicide antidotes Development chemistry and mode of action. Advances in Agronomy 36 265–316. Jepson I.; Lay V. J.; Holt D. C.; Bright S. W. J.; Greenland A. J. (1994). Cloning and characterization of maize herbicide safener-induced cDNAs encoding subunits of glutathione Stransferase isoforms I II and IV. Plant Molecular Biology 26 1855–1866. Jepson I.; Martinez A.; Sweetman J. P. (1998). Chemicalinducible gene expression systems for plants – a review. Pesticide Science 54 360–367. Kreuz K.; Gaudin J.; Stingelin J.; Ebert E.(1991). Metabolism of the aryloxyphenoxypropanoate herbicide CGA 184927 in wheat barley and maize Differential effects of the safener CGA 185072. Zeitschrift fur Naturforschung 46c 901–905. Moreland D. E.; Corbin F. T.; Fleischmann T. J.; McFarland J. E. (1995). Partial characterization of microsomes isolated from mung bean cotyledons. Pesticide Biochemistry and Physiology 52 98–108. CROP PROTECTION BOOKS from the Royal Society of Chemistry Metabolic Pathways of Agrochemicals EDITORS-IN-CHIEF Terry Roberts and David Hutson ISBN 0 85404 489 2 £425.00 Part 1 Herbicides and Plant Growth Regulators ISBN 0 85404 494 9 Part 2 Insecticides and Fungicides ISBN 0 85404 499 X Package price (Parts 1 and 2) Chemistry and Mode of Action of Crop Protection Agents by L.G. Copping and H. G. Hewitt (ISBN 0 85404 559 7 £18.50) Crop Protection Agents from Nature. Natural Products and Analogues Edited by L. G. Copping (ISBN 0 85404 414 0 £140.00) Pesticide Chemistry and Bioscience. The Food-Environment Challenge Edited by G. T. Brooks and T. Roberts (ISBN 0 85404 709 3 £49.50) Agri-Food Quality II. Quality Management of Fruits and Vegetables Edited by M. Hagg R. Ahvenainen A-M Evers and K Tiilikkala (ISBN 0 85404 788 3 £69.50) Order to be sent to Sales & Customer Care Royal Society of Chemistry Thomas Graham House Science Park Milton Road Cambridge CB4 0WF UK. Tel +44 (0)1223 420066. Fax +44 (0)1223 423429. e-mail sales@rsc.org. £225.00 £250.00 SAFENERS Ohkawa H.; Tsujii H.; Ohkawa Y. (1999). The use of cytochrome P450 genes to introduce herbicide tolerance in crops a review. Pesticide Science 55 867–874. Schuler M. A. (1996). Plant cytochrome P450 mono-oxygenases. Critical Reviews in Plant Sciences 15(3) 235–284. Werck-Reichhart D.; Hehn A.; Didierjean L. (2000). Cytochromes P450 for engineering herbicide tolerance. Trends In Plant Science 5(3) 116–123. Wiegand R. C.; Shah D. M.; Mozer T. J.; Harding E. I.; Diaz- Collier J.; Saunders C.; Jaworski E. G.; Tiemeier D. C. (1986). Messenger RNA encoding a glutathione-S-transferase responsible for herbicide tolerance in maize is induced in response to safener treatment. Plant Molecular Biology 7 235–243. 1 5 Pes ti cide Outlook – Fe b r u a ry 2001

ISSN:0956-1250    

DOI:10.1039/b100799h

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

WEED CONTROL USE OF HERBICIDES ON RAILWAY TRACKS IN SWEDEN Lennart Torstensson of the Swedish University of Agricultural Sciences in Uppsala outlines the methods used to clear weeds along railway tracks in Sweden Another important reason for removal of weeds from railway tracks is the working environment for track maintenance employees. The risk of accidents caused by stumbling or slipping on weeds is obvious and may have fatal consequences. A further reason for weed removal is the risk of train wheels skidding causing longer acceleration distances and more seriously extended braking distances which could result in the train being unable to stop at signals. If weeds on the railway embankment become dry during the summer there is always a risk of fire caused by sparks from the wheels.In addition the quality of wooden sleepers is rapidly destroyed when they are lying in polluted watersaturated ballast. Introduction In Sweden removal of weeds along railway lines has been carried out for more than 50 years by application of herbicides. The Swedish national railway network consists in total of about 12,000 km of which 25–30% is treated annually. A specially equipped spray train (Figure 1) is used by trained staff for the purpose. Theoretically there are several alternative methods of removing weeds from tracks i.e. chemical mechanical or thermal. Methods using hot water and steam have been tested but only delayed growth effects have been achieved. Weeds can also be controlled for short periods using open flames but this method is not possible on all types of track because of the fire-sensitive materials used in signal systems.There is also the risk of setting fire to dry vegetation along the tracks. Other approaches for weed management on embankments are use of impenetrable plastic layers along the sides of the embankments and strategies for establishment of weed competitive vegetation along the base of the establishments. The general opinion in Sweden is against use of pesticides and there have been suggestions that weeds on railway tracks could be removed manually. Manual removal would be possible on railway embankments where the ballast consists of gravel. However apart from the manpower required it is a dangerous operation.Weed removal has to be carried out on tracks without disrupting the traffic. Therefore the method used must have a high capacity. Because of this requirement it is difficult to find viable alternatives to chemicals. The Swedish National Rail Administration (BV) has found that weed removal by chemical means is the only practical and economically realistic method and overall is also the least risky method. Why remove weeds? One of the most important reasons for removal of weeds from railway embankments is to retain the quality of the track and to ensure safe railway traffic. The macadam or gravel which are components of the ballast should not become polluted by weeds or decaying plant residues. If this happens the pollutants will fill up the hollow spaces within the ballast resulting in the binding of water.During the winter this water will freeze to ice and swell thereby causing dislocation of the track. Pest ic ide Outlook – Fe b r u a r y 2001 This journal is © The Royal Society of Chemistry 2001 Environmental concerns To obtain good results from herbicide application on railway embankments requires a thorough knowledge of herbicide behaviour and persistence on and in the embankment. By good results is meant acceptable weed control but also the absence of side-effects such as injury to employees or damage to equipment or to the environment along the tracks. Chemical physical and toxicological properties of herbicides approved by the Swedish Chemicals Inspectorate (KemI) are well known but not always as applied to the environment of railway embankments which are characterized by very low contents of clay and organic matter and low biological activity.Herbicides are mainly absorbed to clay and organic matter. If these are low implying a low adsorption capacity the risk of transport out of the target area is obvious. A low content of organic matter normally means low microbial activity. Since the activity of microorganisms is the main factor controlling decomposition of herbicides in soil this results in slow rates of transformation and consequently long persistence times. This means that when a herbicide is to be chosen for use on a railway track it is not enough simply to be well informed about any effects on weeds appearing on the embankment.It is also necessary to know the binding mobility and decomposition of the substance in material from the embankment to be sure that there will be no risks to the surrounding environment. Today BV is investing in far-reaching experiments to identify effective herbicides and methods of application that reduce to a minimum the risk to the surrounding environ- 16 DOI 10.1039/b100802l Figure 1. The train used for full scale spraying operations. The train consists of an engine a staff carriage also containing equipment for recording all data concerning the spraying including GPS and finally a wagon with the spraying equipment and tanks for water supply. Spray booms are mounted on both ends of the wagon.This makes it possible to drive the wagon in either direction spraying only with the ramp at the back of the wagon. ment to BV employees involved in application or to other employees working along the track. A discussion of some of this research is given below. Herbicide testing Studies of herbicides that might be useful on railway tracks can include several steps such as l Gathering relevant information concerning weed effects appearance in the environment through mobility persistence and side-effects as well as methods for analysis of the compound and its metabolites. It is understood that information concerning human toxicity has been or will be evaluated by KemI. l Laboratory studies concerning adsorption to and desorption from material typical for railway embankments in Sweden as well as studies of decomposition in the sa m e material.The aim is collection of data showing kinetics of degradation and influence on rate of degradation of environmental factors. Laboratory studies may also include setting up suitable methods for analysis of the compound and its metabolites in soil and water. This has recently been done for diflufenican (Wennberg and Torstensson 1997) as well as for glyphosate and AMPA (Börjesson and Torstensson 2000). l Minor and full-scale field studies of the herbicide including – weed control effects. – studies of appearance of the compound and its metabolites in the embankment e.g. mobility and persistence. Minor field studies Minor field studies can be carried out on tracks heavily infested by weeds.Test plots are 25 m long with four replicates. To reduce the total length of the experimental WEED CONTROL distance the plots are divided along the middle of the track. The area of a plot is then (3 � 25=) 75 m2. Pesticides are applied using a 3 m boom with 6 VEEJET (11010) nozzles driven by compressed air and a spray volume counted after what is expected to be the volume in a full scale operation.The equipment is mounted on a trolley and speed regulation is done by an MTR 101 engine trolley or similar (Figure 2). Each experiment should include control plots not sprayed between each 5th test plot or at least 4 control plots per experiment. Minor field studies should be repeated at 3–10 geographically different places representing different climatic zones different weed populations and different types of embankments with variations in particle size pH etc.Evaluation of herbicide effects on the weed can be done by grading in a scale from 0 to 5 where 0 is as untreated control and 5 is all vegetation dead. The scale is relatively crude but handy for practical field work. By repeating the estimations at least 2–3 times during the growing period it gives a fairly good comparison oweed effects of different herbicides or dosages. In the practical evaluation half grades can be used. The same method can be used in both minor field studies and in full scale field studies. For studies of appearance of the compound or its metabolites in the embankment samples are taken from a randomly chosen area of 25 � 40 cm within the experimental plot.The uppermost layer (0–10 cm) is sampled by cutting a cubic sample of an area of 9 � 9 cm and 10 cm depth. After that the whole 10 cm layer within the sample area (25 � 40 cm) is removed. Then the procedure is repeated for each of the remaining layers to be sampled. Full-scale field studies Full scale field studies are carried out to verify if a herbicide tested and found useful in minor field studies can also be used on an operative scale. The train used for full scale spraying operations can be seen in Figure 1 with a closer view of the spray boom in Figure 3. The normal speed of operation is 25 km h–1 with the potential for higher speeds.Instead of spraying the herbicide may be wiped onto the weeds using equipment like that illustrated in Figure 4. The Figure 2. Equipment for spraying experimental plots with herbicide in minor field studies. 1 7 Pes ti cide Out look – Fe b r u a ry 2001 Weeds on railway embankments WEED CONTROL Figure 3. Detailed view of one of the spray booms in spray position. The boom can be moved more or less outside the wagon. The speed wind is used to press down the spray liquid against the ballast surface. The boom is equipped with individually fed triple nozzle bodies with diaphragm check valves for drip free shut off. Latin name Figure 4. Equipment specially designed for wiping herbicides on weeds on railway embankments. The wiping unit mixes the concentrated herbicide liquid to the desired concentration and then distributes it to the different ramp sections with its wiping fingers as can be seen in the figure.wiping technique is founded on contact application of herbicide directly on aerial parts of the weed. This type of application eliminates the risk of wind drift. It also reduces the amount of herbicide used since it is only applied on existing weeds. Wiping with this equipment is particularly useful where wind drift has to be avoided or where the application rate has to be as low as possible. However the speed of operation is low 5–8 km h–1. Evaluation of weed control effects as well as studies of the compound’s appearance in the embankment are monitored. Possible transport down to the watertable is studied through sampling in groundwater pipes of the kind described by Börjesson and Torstensson (2000).These are iron standpipes 1.5 m in length and 6 cm in diameter excavated down into the railway embankment as close to the tracks as Pest ic ide Outlook – Fe b r u a r y 2001 18 possible. The upper part of the pipes must not be an impediment for vehicles of any kind in traffic on the tracks. A layer of bentonite is put around the pipes to avoid mechanical transport of contaminated soil particles and surface water along the pipe walls. A layer of gravel filling is put around the bottom of the pipes to allow ground-water to percolate into them. At each sampling sits normally three groundwater pipes are placed in a row with about 10 m spacings.When choosing a herbicide and strategy for weed removal it is important to know what kind of weeds are to be removed. Inventories have been made showing that a large number of plant species both herbaceous and woody are found on the tracks. Examples of frequently appearing species are given in Table 1. Some weed species have caused particular problems on railway embankments. G. boreale and G. verum seem to have become resistent to diuron after it has been used for about 15 years. Glyphosate has no effect on the very common weed Equisetum arvense resulting in an increase of that species after some years of glyphosate application (Figure 5). Table 1. Examples of weed species found along the Swedish railway network.F = frequent VF = very frequent Frequency English name Achillea millefolium Artemisia vulgaris Campanula rotundifolia Equisetum arvense Galium boreale G. verum Gramineae (several spp.) Lapsana communis Linaria vulgaris Melilotus alba Plantago major Ranunculus repens Senecio vulgaris Taraxacum officinale Populus tremula Betula (several species) Picea abies Pinus silvestris Rubus idaeus Salix (several species) VF F F VF VF VF VF F F VF VF F F VF F VF F F F F Yarrow Common mugwort Harebell Common horsetail Northern bedstraw Ladies bedstraw Grass Nipplewort Toadflax Melilot Waybread Buttercup Groundsel Dandelion Aspen Birch Norway spruce Scots pine Raspberry Willow Herbicides Many different herbicides have been used on railway tracks.Active substances used before 1970 include amitrol bromacil diuron monuron and sodium chlorate. From 1974 only diuron formulated as Karmex 80 (800 g a.i. kg–1) was used. However after some years of application in certain areas damage to Scots pine was observed along tracks where diuron had been applied (Torstensson 1983 1985, WEED CONTROL identified in needles and branches of dead and damaged trees. Diuron has also been found to have a very long persistence several years in a railway embankment and in 1993 it was banned for use on Swedish railway tracks. A number of herbicides have been tested for use on Swedish railways.The tests have first identified the weed control effect. If that has been acceptable further tests have investigated mobility and persistence in the embankment. Some herbicides have passed these tests but with other considerations taken into account by BV or KemI few of them have been accepted for practical use. From 1986 glyphosate has been used for weeding of tracks. Since glyphosate has no effect on the very frequent weed common horsetail (E. arvense) that plant has increased in significance on Swedish tracks (Figure 5). Imazapyr provides good control of common horsetail and has been used since 1995. The only two herbicides registered by KemI for use on tracks to-day are glyphosate formulated as Roundup Bio (360 g a.e. l–1) and imazapyr Arsenal 250 (250 g a.i.l–1). The application rates are generally 5 l ha–1 of glyphosate or when there are problems with common horsetail a mixture of 3 l ha–1 glyphosate plus 2 l ha–1 imazapyr the first year followed by 2 l ha–1 imazapyr alone the second year. Figure 5. Common horsetail (Equisetum arvense) growing along railway tracks previously treated repeatedly with glyphosate. 1994). The explanation was that diuron had been transported downward within the embankment and at deeper levels come in contact with roots of Scots pine trees penetrating the embankments. Residues of diuron have been None glyphosate glyphosate 5 l ha–1 5 l ha–1 0 l ha–1 None imazapyr glyphosate + imazapyr 3 + 2 l ha–1 2 l ha–1 Effect on weeds The effects on weeds of the three herbicides used in practical application on railway embankments during the past 10–20 years have been tested in a number of minor field studies all over the country.The weed control effects of the herbicides vary of course depending on geographical site type of vegetation and yearly variations in climatic conditions. If one looks at the mean values for a number of experiments however the differences between the application strategies appear as shown in Table 2. Diuron gave an acceptable effect initially but during its last years of application the effects on certain weeds like G. apparine and G. verum seemed to disappear. Glyphosate has a good weed control effect in most cases on the condition 13 12 10 Table 2.Weed control effects of glyphosate* and imazapyr* on railway embankments after different spraying strategies. SD = standard deviation. N = number of field experiments N Weed control effect ±SD 3rd year 2nd year Treatment 1st year 3.1 ± 0.6 3.8 &pl0.5** 3.0 ± 0.7** 3.7 ± 0.6 4.6 ± 0.4 4.2 ± 0.8 0 l ha–1 15 11 10 * glyphosate formulated as Roundup Bio and imazapyr formulated as Arsenal. ** On condition that common horsetail is rare on the embankment. If it is frequent the effect will go down rapidly. 1 9 Pes ti cide Out look – Fe b r u a ry 2001 WEED CONTROL HERBICIDES ON RAILWAY TRACKS IN THE UK Maintenance of railway tracks in the UK is the responsibility of Railtrack PLC as owners of the 20,000 miles of track in the UK.Since the unchecked growth of vegetation can reduce the operational safety of the line and the life of the track most of the open track is sprayed annually with herbicide by contractors to facilitate maintenance. The aim is to control all weeds on the tracks and injurious or invasive weeds on the trackside. Over the last few years Railtrack has developed a best practice manual for vegetation management based on case studies and increasingly requires its contractors to give careful consideration to sensitive methods of controlling vegetation. In consultation with their contractors Serco Railtest Ltd. and the Environment Agency guidelines have been developed to ensure that control of vegetation is carried out on the basis of an evaluation of the risk to railway operations and the environment.Herbicides used Railtrack uses herbicides that work as selectively as possible. Three main herbicides are in current use l l l Roundup (glyphosate) – a foliar-acting contact herbicide Freeway (diuron) – a residual herbicide which remains in the soil killing seeds as they germinate Garlon 4 (triclopyr) – a selective herbicide which is specifically designed to kill broadleaf weeds and woody scrub growth These herbicides are normally applied using a fleet of specially designed Multi Purpose Vehicles (MPVs) fitted with spraying arms backed up by back-pack spraying in stations and sensitive locations. These MPVs are also used to apply anti-skid Sandite coating and water-jet conditioning of track. Environmental protection Railtrack works with the Environment Agency (EA) the Scottish Environment Protection Agency (SEPA) English Nature Scottish Natural Heritage Countryside Commission for Wales and the water companies to agree a list of sites for protection against potentially damaging effects of herbicide spraying.In these areas for example near water courses near abstraction sites for drinking water or where the ecology needs special protection the types of herbicides used by contractors are restricted. In 1999 728 such sites were agreed with these parties. Railtrack is also collaborating with the EA to carry out research into the leaching of herbicides. To minimise the effects on ecology all Railtrack zones have locally held databases. In all these databases contain over 3000 listed assets including sites of conservation interest and protected trees.Efforts are also made to protect and preserve wildlife wherever possible although in certain circumstances there is of course a need to control vermin. The following are two examples of ways in which Railtrack are seeking to protect the environment within its track maintenance programme. Protecting the sand lizard Railtrack is tailoring lineside works to help preserve the rail corridor as a linking habitat to Europe’s most northerly colony of the rare sand lizard (Lacerata agilis) on the Sefton coast on Merseyside. This is thanks to a joint initiative with English Nature the Life Fund Project Sefton Metropolitan Council and Jarvis Facilities Management on the Merseyrail Northern Line.Creating green corridors Within the Capital Greenlinks Lineside Regeneration Projects in South London Railtrack is improving the management and diversity of rail lines and linking public spaces with green corridors. At Wandsworth a seamless parkland landscape between the Common and the railway is being created with improvements to a mile and a half of rail corridor. Biodiversity Action Plans Railtrack has worked recently with the Wildlife Trusts and English Nature to develop a biodiversity action plan for their East Anglia Zone. The plan made available to contractors identifies the location of protected sites or species on the railway infrastructure on best practice for their management. For further information on Railtrack see http://www.railtrack.co.uk Pesti c ide Outlook – Fe b r u a r y 2001 20 that common horsetail is rare on the embankment.I f i t occurs a few years of treatment with glyphosate may render it dominant (Figure 5) but in such cases a mixture of glyphosate and imazapyr gives a good effect especially if followed the next year with a treatment of imazapyr alone. Normally there is then no need of any herbicide during the third year in southern and central Sweden. In the north of Sweden there may be no need for herbicide during the fourth year. Figure 7. Half-lives of diuron glyphosate and imazapyr in railway embankments. SD = standard deviation. Number of field experiments glyphosate 10 imazapyr 20 diuron 10. glyphosate 10 imazapyr 20 diuron 10. Mobility and decomposition Soil factors and climatic conditions influence mobility and decomposition of the herbicides.Diuron was very mobile in the railway embankment (Figure 6). All the herbicides studied move downward through the uppermost 20–30 cm of the embankment the part built up of macadam or gravel. This is probably a result of mechanical downward particle transport caused by the train traffic and transport in solution due to rain. The particles carry the applied herbicides adsorbed to them. With regard to glyphosate the main proportion of the herbicide is found in the uppermost 20 cm although amounts above the detection limit may be found down to a depth of 50–60 cm on certain sites. The main proportion of imazapyr is found in the upper 30 cm but amounts above the detection limit have been found down to a depth of 60–80 cm on several sites (Figure 6).Figure 6. Mobility of diuron glyphosate and imazapyr in railway embankments. Number of field experiments Diuron has a very long persistence in railway embankments (Figure 7). In spite of the fact that it has not been used since 1993 diuron and its metabolite demethylated diuron are still detectable in the embankments. Glyphosate and imazapyr have considerably shorter half-lives than diuron. Minor amounts of them however as well as of the glyphosate metabolite AMPA may be found a long time (1–2 years) after application. At sampling of groundwater pipes along tracks transport down to the groundwater has been detected for diuron and its demethylated metabolite.Glyphosate and imazapyr applied at the recommended rates have not been detected in WEED CONTROL amounts above 0.1 µg l–1 in water taken from the groundwater pipes. Conclusions l Weeds on railway tracks have to be removed to retain quality of track and to ensure safe railway traffic. l Acceptable weed control on railway embankments requires thorough knowledge of the weed control effect of the herbicide as well as its behaviour and persistence on and in the embankment. l To gather this knowledge there is a great need for testing of herbicides before they are introduced to the specific environment that a railway embankment provides. l From such studies it is an obvious fact that herbicides behave differently from what is known from their use on agricultural land usually with greater mobility and longer persistence.l After careful testing and evaluation of herbicides it is possible to select substances for weed control on railway tracks that fulfil high demands for a good weed control effect as well as a minimal influence on the surrounding environment. References Börjesson E.; Torstensson L. (2000). New methods for determination of glyphosate and (aminomethyl)phosphonic acid in water and soil. Journal of Chromatography A 886 207–216. Torstensson L. (1983). Investigations of mobility and decomposition of diuron in railway embankments. Swedish Environmental Protection Agency SNV PM 1764 43 pp. (in Swedish) Torstensson L. (1985). Further investigations of mobility and decomposition of diuron in railway embankments. Swedish Environmental Protection Agency SNV PM 2001 20 pp. (in Swedish) Torstensson L. (1994). Mobility and transformation of diuron in railway embankments. Proc. 5th Int. Workshop. Environmental Behaviour of Pesticides and Regulatory Aspects Brussels April 26–29 1994. Copin A. Houins G. Pussemier L. Salembier J.F. (Eds.) Developed from a symposium sponsored by the European Commission within the framework of COST Action 66 366–371. Wennberg E; Torstensson L. (1997). Gas-chromatographic method for determination of diflufenican in soil. International Journal of Environmental Analytical Chemistry 67 73–79. Dr Lennart Torstensson is Associate Professor of Microbiology at the Swedish University of Agricultural Sciences Uppsala Sweden. 2 1 Pes ti cide Out look – Fe b r u a ry 2001

ISSN:0956-1250    

DOI:10.1039/b100802l

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

Figure 1. Macroconidia RICE BLAST DISEASE Importance of the disease Rice blast disease is distributed in about 85 countries in all continents where the rice plant is cultivated in both paddy and upland conditions. Although the damage is very much influenced by environmental factors this disease is recognized to be one of the most serious diseases of the rice plant worldwide. Causal organism Rice blast is caused by the Ascomycete fungus Magnaporthe grisea Barr (anamorph Pyricularia grisea Sacc. synonym P. oryzae Cav.). Pyriform macroconidia ca. 20 � 10 mm (Figure 1) are produced on conidiophores which protrude from lesions on plants. These germinate and develop an appressorium (Figure 2) at the tip of the germ tube which attaches to the surface of plant tissues; an infection-peg from the appresorium penetrates into plant tissues.The wall of conidiophores and appressorium are pigmented by melanin. Symptoms The fungus is able to infect and produce lesions on all organs of the rice plant except the root. Leaf blast (Figure 3) When the fungus attacks a young leaf purple spots can be observed after an incubation period changing into a spindle shape which has a gray centre with a purple-to-brown border and then surrounded by a yellow zone as time passes. Brown Hajime Kato Director of the Japan Plant Protection Association and former Head of the Department of Plant Protection National Agricultural Research Centre Ministry of Agriculture Forestry and Fisheries and Professor of Plant Pathology at Kobe University in Japan introduces a series of articles on an important disease affecting rice growing worldwide Pes ti cide Out look – Fe b r u a ry 2001 This journal is © The Royal Society of Chemistry 2001 spots appear only on the older leaves or leaves of resistant cultivars.In young or susceptible leaves lesions coalesce and cause withering of the leaves themselves especially at the seedling and tillering stages. Lesion formation on the n-leaf (where n is the top developing leaf) causes shortening of the n + 1 leaf sheath and the n + 2 leaf blade with consequent stunting of the whole plant. Neck rot and panicle blast (Figure 4) Infection to the neck node produces triangular purplish lesions followed by lesion elongation to both sides of the neck node – symptoms which are very serious for grain development.When young neck nodes are invaded the panicles become white in colour – the so-called ‘white head’ that is sometimes misinterpreted as insect damage. Later infection causes incomplete grain filling and poor grain quality. Panicle branches and glumes may also be infected. Spikelets attacked by the fungus change to white in colour from the top and produce many conidia which become the inoculum source after heading. Collar rot (Figure 4) Infection at the junction of the leaf blade and the leaf sheath i.e. the collar readily occurs and causes browning of the tissues and withering of the leaves. Node blast During heading the stem nodes which appeared from the leaf sheaths are attacked and sometimes cause lodging.Diseased nodes are brown or black in color. DOI 10.1039/b100803j RICE BLAST CONTROL Figure 2. Appressoria 2 3 Figure 3. Leaf blast lesions RICE BLAST CONTROL Disease cycle A disease cycle begins when a blast spore infects and produces a lesion on the rice plant and ends when the fungus sporulates repeatedly for about 20 days and disperses many new airborne spores. Under favourable moisture and temperature conditions (long periods of plant surface wetness high humidity little or no wind at night and night temperatures between 12– 32 °C) the infection cycle can continue. In the canopy of rice plants newly developed leaves act as receptors for the spores. The maximum number of spores produced was 20,000 on one lesion on leaves and 60,000 on one spikelet in one night.Lesions on leaves become an inoculum source for panicles. Overwintering The pathogen can continue to live in plants from one crop season to another in the tropics or survive in the temperate zone on residues of diseased plants or seeds or on ratoons of stubble. Weeds can act as alternative hosts for the disease in glasshouse tests but their role in the field in unclear. Figure 4. Neck rot and collar rot 24 Pest ic ide Outlook – Fe b r u a r y 2001 Incubation period Incubation period y can be expressed by y = –0.45 + 16.3 at seedling stage and y = –0.60 + 20.8 at tillering stage where x is the average daily temperature. The incubation period is longer from spikelets (5–7 days) branch nodes and neck nodes (10–12 days) respectively.Lesion expansion Exposure of the diseased plants to higher temperatures e.g. around 32 ºC causes lesions to expand rapidly in the first 8 days and level off shortly thereafter then a swift cessation of lesion enlargement takes place. On the other hand the rate of enlargement is slow and constant over the 20-day period at lower temperatures e.g. 16 ºC. Lesions expand slowly and cessation occurs gradually in the intermediate temperature regime 20–25 ºC. Yield loss Severe outbreak of leaf blast causes stunting and the development of small panicles. Early infection of neck nodes causes white head and yield loss y expressed as y = 1.45x to y =2.55x (where x is the percentage of white head) and y = 0.31x to y = 0.57x (where x is the percentage of diseased neck node); x is surveyed on the 30th day after heading.15 years of data collected in Japan shows that y varies considerably under different circumstances from 1–100%. Control measures Burning or composting of diseased tissues Diseased straw and stubble must be burned or composted otherwise they can become inoculum sources for the next crop season. Healthy seed To obtain healthy seeds the seeds must be collected from the field located under unfavorable conditions for the pathogen and fungicide must be applied if necessary. Gravity separation methods for seeds are useful. Salt solution 200 g l–1 or ammonium sulfate solution 230 g l–1 is used to separate sufficiently matured seeds followed by chemical treatment for seed disinfection against a range of pathogens.Fertilizer management Nitrogen and phosphorus content in the plants affects disease proneness. Excess nitrogen fertilizer encourage disease development while silica application reduces disease development. Therefore the amount and type of fertilizer must be carefully decided upon according to the cultivar used soil condition climatic conditions and disease risk. Cultural systems Sowing into water eliminates disease transmission from seeds to seedlings because of the anaerobic condition that is unfavorable to the pathogen. On the contrary sowing on wet soil allows seed transmission. Shade affects disease occurrence because of the longer wet condition.Chemical control Many fungicides are used against blast disease including benomyl fthalide edifenphos iprobenfos tricyclazole isoprothiolane probenazole pyroquilon felimzone(= meferimzone) diclocymet carpropamid fenoxanil and metominostrobin and antibiotics such as blasticidin and kasugamycin. Systemic fungicides are widely used to protect against leaf blast by seedling application and also to protect against panicle blast when applied more than 20 days before heading. The composition amount timing and application method of fungicide applied depends on the disease forecast or level of disease present. To avoid pathogen resistance problems chemical control must involve the use of chemicals with different modes of action – see the three succeeding papers by Iwata Uesugi and Kurahashi respectively which illustrate how wellestablished chemicals with different modes of action can continued to find a place in protection against rice blast from their contribution toward the avoidance of resistance problems.Resistant cultivars Race-specific and race-nonspecific resistant cultivars have been bred all over the world. Based on the information of distribuon of races these cultivars can be selected. JAPAN CROP PROTECTION ASSOCIATION (JCPA) JCPA is the non-profit organization of Japanese manufacturers formulators and distributors of agricultural crop protection products (CPPs). Founded in 1953 JCPA represents more than 90 companies which manufacture sell and distribute CPPs in Japan Objectives JCPA promotes mutual information exchange and cultivates mutual friendship among its members.Also in conformity with FAO International Code of Conduct on the Distribution and Use of Pesticides JCPA seeks to l to supply necessary CPPs required by the public and to secure enough food and environmental conservation. l to promote the proper use of CPPs and to secure the safety in human health and environment. l to cope with the issues surrounding CPPs industry and to contribute to the sound progress of the industry Priorities l to promote technical developments of CPPs for increasing the productivity of agricultural products and for protecting the green land. l to take the safety measures for protecting the health of users and consumers and for conserving the environment.l to intensify the public relations about CPPs for promoting their proper use and understanding. l to streamline the distribution channels of CPPs for stable supply and cost reduction. l to participate in the international activities of the related organizations for promoting the increase of food production and safe use of CPPs. For further information contact Japan Crop Protection Association 5-8 1-Chome Muromachi Nihonbashi Chuo-Ku Tokyo 103 Japan [Tel Tokyo +81 (3)3241-0215; Fax +81(3)3241-3149; http://www.jcpa] RICE BLAST CONTROL Forecasting systems Forecasting systems have been developed in some countries and being used effectively. Conclusion Blast disease can be controlled by an integrated management system using a variety of methods – resistant cultivars cultural practices and chemical application – based on the information from disease forecasting systems. Chemical methods of control will continue to have a role to play in fighting blast and there follow papers on 3 classes of such chemicals—probenazole (a plant activator) choline biosynthesis inhibitors (CBIs) and melanin biosynthesis inhibitors (MBIs). Although many of these chemicals have been in use for some time they illustrate the value in retaining different classes of chemicals to help in the fight against resistance development. Further reading Inoue S. Pesticide Outlook 1990 1(4) 31. Webster R. K.; Gunnell P. S. (1992). Compendium of rice diseases. The American Phytopathological Society St Paul MN USA. Zeigler R. S.; Leong S. A.; Teng P. S. (Eds) (1994). Rice blast disease. CAB International,Wallingford UK. 2 5 Pes ti cide Outlook – Fe b r u a ry 2001

ISSN:0956-1250    

DOI:10.1039/b100803j

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

RICE BLAST CONTROL Introduction The phosphorothiolate fungicides including iprobenfos and edifenphos were introduced in Japan as rice blast fungicides in 1963 and are still being used as one of the major groups of rice blast fungicides; a related dithiolane fungicide isoprothiolane has been used against blast since 1975 (Figure 1). Iprobenfos and isoprothiolane have systemic action and are used mainly as granules for application on the surface of paddy water (soil application). On the other hand edifenphos seems to be less soluble in water and less stable in plants and hence is most effective by foliar application. This short article outlines the development of our knowledge of the mode of fungicidal action of phosphorothiolates and isoprothiolane as choline biosynthesis inhibitors (CBIs) and relates this to their influence on mammals and insects.FUNGAL CHOLINE BIOSYNTHESIS – A TARGET FOR CONTROLLING RICE BLAST Yasuhiko Uesugi formerly of the National Institute of Agro-Environmental Sciences Japan discusses the mode of action and biological activity of phosphorothiolate and related fungicides Figure 1. Chemical structures of CBIs and related fungicides fungal metabolism of both groups of fungicides. The wildtype strains detoxified phosphoramidates by N-demethylation and hydroxylation of the higher alkyl group at the (w– 1) position and seemed to activate phosphorothiolates by a metabolism accompanied by cleavage of the P–S bond. These detoxifying and activating metabolic reactions were mediated by mixed function oxygenases.In the laboratory mutants these reactions were almost lost and this loss of the metabolism may explain the negative cross-resistance between phosphorothiolates and phosphoramidates. With this type of fungal mutant cross-resistance between isoprothiolane and phosphorothiolates and negative cross-resistance between isoprothiolane and phosphoramidates were also observed so that similar activation in the fungicidal action of isoprothiolane has been suggested though the details of the metabolism have not been studied. Figure 2. Two major pathways of phosphatidylcholine biosynthesis showing the site of action of CBI fungicides 26 Mode of action of phosphorothiolate and related fungicides Initially the mode of action of phosphorothiolate fungicides was proposed to be interference with biosynthesis of chitin a component of the fungal cell wall but this was later rejected as a secondary effect of the fungicides.During these studies disorganization of the fungal cell membrane with leakage of cytoplasmic substances from the fungal cells was often observed leading to the conclusion that the mode of action is inhibition of the biosynthesis of phosphatidylcholine an important component of the fungal cell membrane (Kodama et al. 1979 1980). Two major pathways have been known for phosphatidylcholine biosynthesis (Figure 2). In Greenberg’s pathway the transmethylation occurs at the final step while in Kennedy’s pathway it occurs at the preliminary step yielding choline a precursor to be further incorporated into phosphatidylcholine.Using 13C labeling studies Yoshida showed that Kennedy’s pathway is the principal route of phosphatidylcholine biosynthesis in the rice blast fungus (Yoshida 1984) and that the transmethylation yielding choline is inhibited by phosphorothiolates and isoprothiolane (Figure 2). Phosphorothiolates and isoprothiolane were thus classified as choline biosynthesis inhibitors (CBIs). Interesting relationships have been observed between phosphorothiolate and other rice blast fungicides (Uesugi and Takenaka 1993). Laboratory fungal mutants resistant to phosphorothiolates have proved to be specifically sensitive to a group of experimental fungicides having phosphoramidate structure.The phosphoramidates exhibited however little activity against normal wild-type strains of the fungus. This negative cross-resistance has been studied in relation to Pest ic ide Outlook – Fe b r u a r y 2001 This journal is © The Royal Society of Chemistry 2001 (* = transmethylation steps) DOI 10.1039/ b100804h The fungal activation of phosphorothiolates was further ascertained by antagonistic action on wild-type fungal strains with another group of fungicides – the demethylation inhibitor (DMI) type of sterol biosynthesis inhibiting (SBI) fungicides which are thought to be inhibitors of mixed function oxygenases. Possibly DMIs antagonize the fungicidal activity of phosphorothiolates by interfering with enzymatic activation. Activation of phosphorothiolates was thus suggested but the activated form of the fungicides seemed to be an unstable intermediate or a by-product produced during the course of cleavage of the P–S bond.Fungicidal spectrum of CBIs CBIs act against several diseases of rice plants but their effectiveness against diseases other than rice blast is not reliable enough to enable them to be used as major protectants. The rice blast fungus seems to have peculiar physiological characteristics yielding sensitivity to CBIs. Possible hypotheses are that the fungicides are specific inhibitors of choline biosynthesis and phosphatidylcholine biosynthesis proceeds exclusively through the Kennedy’s pathway in this fungus but not in most other fungi and/or that only this fungus is equipped with an enzymatic system to activate phosphorothiolates and isoprothiolane; these hypothesis have not been examined.Resistance to CBI fungicides among various strains of the rice blast fungus has been an important problem in practice and also an interesting physiological phenomenon. As stated before laboratory resistance to CBIs seemingly caused by decreased activation has been observed and this resistance was accompanied by sensitivity to phosphoramidates by decreased detoxification. Resistance to CBIs was later observed in the field but the field resistance differed from the laboratory resistance in that negative cross resistance to phosphoramidates was not observed in most resistant field isolates. In CBI-resistant field isolates activation of phosphorothiolates accompanied by P–S cleavage decreased but another mode of metabolism S–C cleavage increased.Detoxification of phosphoramidates still remained in the resistant field isolates though the detoxifying metabolism was slightly modified decreasing N-demethylation and increasing hydroxylation. In other words the field resistance seemed to be caused by a change in the mode of fungicide metabolism by mixed function oxidases not by total loss of it. Field resistance to CBI fungicides in the rice blast fungus has been observed when this group of fungicides were used successively and exclusively but it is not a problem when fungicides with different modes of action are used in turn. Low mammalian toxicity of CBIs Choline is an important component for animals including mammals and insects in transmission of stimuli within their nervous systems.It also plays other roles such as prevention of dysfunction diseases like fatty liver. Biosynthesis of choline in mammals however seems poor so that choline has been classed as a nutrient or vitamin for mammals; this explains why CBIs display very low mammalian toxicity. This situation is comparable to that of sulfonylurea and imidazolinone herbicides which inhibit biosynthesis of branched chain amino acids such as valine leucine and RICE BLAST CONTROL isoleucine and to that of glyphosate which interferes with biosynthesis of aromatic amino acids such as phenylalanine tyrosine and tryptophan. Inhibitors of the biosynthesis of mammalian vitamins or nutrients like choline and the above amino acids are useful candidate pesticides with low mammalian toxicity.Influence of CBIs on insects CBI fungicides sometimes control leafhoppers and planthoppers on rice plants; e.g. isoprothiolane was registered as an insecticide to control brown planthoppers on rice plants in Japan. It is not a quick-acting insecticide but reduces insect populations. Could this be related to the inhibitory action on choline biosynthesis? Choline is known to accelerate growth of insects such as rice stem borer in laboratory studies but its necessity as an insect nutrient has not been demonstrated. Moreover symbiotic microbes which are common in insects may synthesize choline and supply it to host insects.If choline biosynthesis is vital to insects and/or their symbiotic systems its inhibition may be lethal to them though this has not been established as the mode of action of CBI fungicides on insects. Future outlook CBI fungicides such as phosphorothiolates and isoprothiolane were developed following the discovery that sensitivity to chemical inhibition of fungal choline biosynthesis is a specific characteristic of the rice blast fungus; there is a possibility of development of new fungicide molecules with a similar action. Although existing CBI fungicides are already old this group of fungicides have been and will continue to be necessary as one of the major fungicide classes used against the disease and required to give the diversity of action needed in the fight against resistance development.The development of new CBIs is also encouraged by their low toxicity to mammals and their secondary insecticidal action reducing the population of insects such as plant hoppers and leaf hoppers. References Kodama O; Yamada H.; Akatsuka T. (1979) Kitazin P inhibitor of phosphatidylcholine biosynthesis in Pyricularia oryzae. Agricultural and Biological Chemistry 43(8) 1719–1725. inhibitor of phosphatidylcholine biosynthesis in Pyricularia oryzae. Agricultural and Biological Chemistry 44(5) methylation from methionine into choline in the intact mycelia of Pyricularia oryzae by 13C NMR under the influence of Kodama O.; Yamashita K.; Akatsuka T. (1980) Edifenphos 1015–1021. Yoshida M.; Moriya S.; Uesugi Y. (1984) Observation of transfungicides. Journal of Pesticide Science 9(4) 703–708. Uesugi Y.; Takenaka M. (1993) Mechanism of action of phosphorothiolate fungicides. Proceedings of the 10th International Symposium on Systemic Fungicides and Antifungal Compounds 1992 159–164. Yasuhiko Uesugi worked as a scientist in Japanese national research institutes dealing with pesticides for 32 years and was head of the Division of Pesticides and of the Laboratory of Fungicide Chemistry at the National Institute of Agroenvironmental Sciences (formerly Agricultural Sciences). Later he worked for 9 years in pesticide research and development at Ube Industries Ltd. 2 7 Pes ti cide Out look – Fe b r u a ry 2001

ISSN:0956-1250    

DOI:10.1039/b100804h

出版商:RSC    

年代:2001

数据来源: RSC

摘要:

RICE BLAST CONTROL l l PROBENAZOLE – A PLANT DEFENCE ACTIVATOR Michiaki Iwata from the Meiji Seika Kaisha Ltd. Pharmaceutical Research Centre in Yokohama in Japan discusses the mode of action of probenazole a leading agent for the control of rice blast l rice plant tissue or in an environment such as paddy water it does not reduce virulence of the fungus it does not inhibit biosynthesis of fungal melanin pigment which is essential for penetration of the fungus into the plant tissue Introduction Probenazole (3-allyloxy-1,2-benzisothiazole-1,1-oxide) (Figure 1) is a protectant developed by Meiji Seika Kaisha Ltd. for rice blast control. Oryzemate containing probenazole has been widely used against blast by Japanese farmers since 1975 because it provides good long-lasting control when applied on a paddy field or in a seedling box.After application to rice plants probenazole is absorbed by the roots then systemically transferred to the whole plant almost completely controlling leaf blast for 40–70 days after application. Despite extensive use over many years no development of resistance in the target fungus has been observed. Figure 1. Structure of probenazole Activation of the natural plant disease defence system Most plants have the ability to escape invasion of pathogens by using defence systems even if they do not have a specific disease resistance gene. There is a delicate relationship between plant and pathogen. When environmental conditions such as temperature and humidity are favourable for the pathogen the pathogen can easily invade the plant.When the defence system of the plant functions effectively on the other hand the plant can overcome pathogen attack. Our studies show that probenazole activates the disease defence system of a plant – an unusual mode of action for a disease control chemical previously unreported. By activating the plant defence system probenazole alters the balance of the plant–pathogen relationship in favour of the plant. Non-fungicidal protection Our experiments on the effect of probenazole on the blast fungus have shown it does not have any fungicidal activity against the fungus it is not changed to a fungicidal substance within the Pest ic ide Outlook – Fe b r u a r y 2001 This journal is © The Royal Society of Chemistry 2001 l Hence although probenazole gives excellent control of blast it and its metabolites do not affect the growth or infectivity of the blast fungus.Activation of defence-related phenylpropanoid pathway Activities of enzymes in the phenylpropanoid pathway such as phenylalanine ammonia-lyase peroxidase and polyphenoloxidase are enhanced in rice plants treated with probenazole especially in plants inoculated with the blast fungus after probenazole application (Iwata et al. 1980). The phenylpropanoid pathway plays an important role in the plant defence system; when the plant is being infected lignin is synthesised and acts as a physical barrier against pathogen invasion and a phytoalexin with antimicrobial activity is produced.These contribute to the limitation of pathogen invasion in the plant tissue. Our results show that probenazole activates the phenylpropanoid pathway and thereby enhances the defence response in the plant. Accumulation of fungicidal substances We found that fungicidal substances accumulate within the tissue of the treated and inoculated rice leaf. Since probenazole and its metabolites do not have any fungicidal activity we thought that these substances originated from the rice plant. They were identified as hydroxy unsaturated fatty acids derived from a-linolenic acid (Shimura et al. 1983). We also proposed a biosynthesis pathway of these hydroxyl unsaturated fatty acids as follows a-linolenic acid cut off by phospholipase A2 from phospholipid in cell plasma membrane is peroxidized into hydroperoxylinolenic acids by lipoxygenase; then the hydroperoxides are rapidly reduced to hydroxides (Figure 2).Activities of both enzymes in the rice leaf were enhanced when the plant was inoculated with a resistant-reaction-inducing incompatible race of the blast fungus suggesting participation of both enzymes in defence response. The hydroperoxide synthesis forms part of the octadecanoid (18-carbon) pathway by which the plant hormone jasmonic acid an endogenous elicitor of defence 28 DOI 10.1039/ b100805f Figure 2. Octadecanoid cascade in plant activated by probenazole. gene expression and phytoalexin biosynthesis (Nojiri et al. 1996) is synthesized. Amplification of superoxide production Superoxide production in a protoplast prepared from rice leaves treated with probenazole was amplified by treatment with an elicitor extracted from the blast fungus cell wall showing that probenazole amplifies superoxide production in leaves attacked with the pathogen.Superoxide was released from the protoplast within several seconds after elicitor treatment suggesting that superoxide production is one of the earliest defence responses in the rice plant. In many plants production of reactive oxygen including superoxide is part of the hypersensitive response which is a powerful defence mechanism against pathogen attack (Doke et al. 1983). Since the production of reactive oxygen proceeds with rapid oxygen consumption this phenomenon is called an oxidative burst.Superoxide after generation from the NADP(H) oxidase system in plant plasma membrane is readily dismuted into hydrogen peroxide which is the most stable form of reactive oxygen. It has been reported that hydrogen peroxide is implicated in the direct killing of invading pathogen in the cross-linking of cell wall sugar proteins in the plant cell death process as a cytotoxin and in the induction of defence gene expression. Activation of the signal transduction system Plants have intercellular and intracellular signal transduction systems which transfer information from cell to cell and RICE BLAST CONTROL from outside to inside a cell relating to stresses pathogen attack wounding etc. We have observed that the defence system of the rice plant is activated through cell membrane and intracellular signal transduction pathways after treatment with a blast fungus elicitor (Kanoh et al.1993). One of the metabolites of probenazole in the rice plant accelerated an activity of cell membrane GTPase which plays an important role in membrane signal transduction from the receptor of the elicitor (Sekizawa et al. 1995). Also the expression of protein kinase C to regulate the intracellular signal transduction is induced by treatment with probenazole (Kiribuchi et al. 1998). These observations suggest that cell membrane and intracellular signal transduction systems in the rice plant are activated by probenazole. The rice plant with an activated defence signal transduction pathway can more quickly respond to the attack of pathogen and hence escape infection.Rice genes expressed by probenazole We hypothesized that the sensitization of the disease defence system in plants treated with probenazole would be brought about by a response involved with gene transcription. We screened for rice expression induced by probenazole application to prove this hypothesis and found a new rice gene PBZ1 (Midoh and Iwata 1996). The amino acid sequence estimated from the nucleic acid sequence of the PBZ1 gene showed about 30% homology with PR (pathogenesisrelated)-10 protein. This PR protein is induced after an infection of pathogen and is thought to be an infection response and defence-participating protein.When rice plants untreated with probenazole were inoculated with the blast fungus the PBZ1 gene was also induced in the rice leaf tissue. Expression of the PBZ1 gene induced by inoculation with the incompatible fungus occurred earlier than with the compatible fungus. These results show that the PBZ1 gene product is a kind of PR protein and that probenazole induces this PR protein. Expression of the PBZ1 gene was highly induced in a lesion-mimic rice mutant in which defence responses were extremely expressed (Takahashi et al. 1999). Although the function of PBZ1 protein in disease defence is still unclear the expression of the PBZ1 gene is clearly correlated with expression of disease resistance. Sakamoto et al. (1999) isolated another rice gene RPR1 (rice probenazole responsible gene) by a differential display technique.Transcription of the RPR1 gene was detected 3 days after treatment of probenazole and reached its maximum level at 6–9 days. Mode of the RPR1 expression in probenazole-treated rice plants correlated well with protection of the blast. The RPR1 protein deduced from the amino acid sequence contains a nucleotide binding site (NBS) and leucine-rich repeats (LRR). Interestingly NBS and LRR are common characteristics in the proteins coded within disease resistance genes isolated from many plants including rice. These characteristics suggest that expression of the RPR1 gene induced by probenazole leads to induction of a disease resistance response. Recently researchers have reported that many defence related genes in the rice plant are induced by application of probenazole (Shimono et al.2000; Schaffrath et al. 2000). 2 9 Pes ti cide Out look – Fe b r u a ry 2001 References RICE BLAST CONTROL Our conclusion on the mode of action of probenazole is that it prevents the invasion of pathogen by inducing many defence genes through the signal transduction pathway (Figure 3). The future Several chemicals that activate the defence system of plants like have now been reported. Benzo(1,2,3)thiadiazole-7- carbothioic acid S-methyl ester (acibenzolar-S-methyl) (Figure 4) induces systemic acquired resistance (Friedrich et al. 1996) which is one of the natural defence systems of plants. This compound has been introduced commercially by Novartis for control of a range of plant diseases.The modes of action of probenazole and acibenzolar-S-methyl are not the same because expression of the RPR1 gene is induced by acibenzolar-S-methyl but that of the PBZ1 gene is not. Figure 4. Structure of acibenzolar-S-methyl. Plant activators such as probenazole and acibenzolar-Smethyl usually do not have biocidal activity have good environmental safety are good protectants act against a wide range of plant pathogens (fungi bacteria and viruses) and have a low risk of development of pathogen resistance. It is expected that plant activators will occupy a major position as agrochemicals for controlling diseases and insects early in the 21st century. Pest ic ide Outl ook – Fe b r u a r y 2001 30 2 Figure 3.Hypothetical action site of probenazole in disease defence system of rice plant. PBZ1,RPR1 probenazoleinduced gene products; PLA phospholipase A2; LOX lipoxygenase; PAL phenylalanine ammonia-lyase; TAL tyrosine ammonia-lyase; POX peroxidase; CH2=CH2 ethylene; G GTP binding protein; PIP2 phosphatidylinositol 4,5-bisphosphate; IP3 inositol 1,4,5-triphosphate; DAG diacylglycerol; ER endoplasmic reticulum. Doke N. (1983) Involvement of superoxide anion generation in the hypersensitive response of potato tuber tissues to infection with an incompatible race of Phytophthora infestans and to the hyphal wall components. Physiological Plant Pathology 23 345–357. Friedrich L.; Lawton K.; Ruess W.; Masner P.; Specker N.; Rella M.G.; Meier B.; Dincher S.; Staub T.; Uknes S.; Metraux J-P.; Kessmann H.; Ryals J. (1996) A benzothiadiazole derivative induces systemic acquired resistance in tobacco. Plant Journal 10 61–70. Kanoh H.; Haga M.; Iwata M.; Sekizawa Y. (1993) Transmembrane signaling operated at rice blade cells stimulated by blast fungus elicitor I. Operation of the phospholipase C system. Journal of Pesticide Science 18 299–308. Kiribuchi K.; Dunlap D. Y.; Matsumura F.; Yamaguchi I. (1998) Protein kinase C as a biomarker for assessing the effect of environmental stress and fungal invasion on plant defence mechanism. Journal of Pesticide Science 23 123–128. Iwata M.; Suzuki Y.; Watanabe T.; Mase S.; Sekizawa Y. (1980) Effect of probenazole on the activities of enzymes related to the resistant reaction in the rice plant.Annals of the Phytopathological Society of Japan 46 297–306. Midoh N.; Iwata M. (1996) Cloning and characterization of a probenazole-inducible gene for an intracellular pathogenesisrelated protein in rice. Plant Cell Physiology 37 9–18. Nojiri H.; Sugimori M.; Yamane H.; Nishimura Y.; Yamada A.; Shibuya N.; Kodama O.; Murofushi N.; Omori T. (1996) Involvement of jasmonic acid in elicitor-induced phytoalexin production in suspension-cultured rice cells. Plant Physiology 110 387–392. Sakamoto K.; Tada Y.; Yokozeki Y.; Akagi H.; Hayashi N.; Fujimura T. Ichikawa N. (1999) Chemical induction of disease resistance in rice is correlated with the expression of a gene encoding a nucleotide binding site and leucine-rich repeats.Plant Molecular Biology 40 847–855. Schaffrath U.; Zabbai F.; Dudler R. (2000) Characterization of RCI-1 a chloroplastic rice lipoxygenase whose synthesis is induced by chemical plant resistance activators. European Journal of Biochemistry 267 5935-5942. Sekizawa Y.; Aoyama H.; Kimura M.; Yamaguchi I. (1995) GTPase activity in rice plasma membrane preparation enhanced by a priming effector for plant defence reactions. Journal of Pesticide Science 20 165–168. Shimono M.; Yazaki J.; Nakamura K.; Kishimoto N.; Kikuchi Takahashi A.; Kawasaki T.; Henmi K.; Shii K.; Kodama O.; Satoh H.; Shimamoto K. (1999) Lesion mimic mutants of rice with alterations in early signaling events of defence.Plant Journal 17 535–545. S.; Kubo N.; Kadowaki K.; Mochizuki A.; Yamamoto K.; Sasaki T.; Nishiguchi M. (2000) Analysis of gene expression in rice plants treated with an inducer of disease resistance probenazole using DNA microarray. . Annals of the Phytopathological Society of Japan 66 115–116 (Japanese abstract). Shimura M.; Mase S.; Iwata M.; Suzuki A.; Watanabe T.; Sekizawa Y.; Sasaki T.; Furihata K.; Seto H.; Otake N. (1983) Anti-conidial germination factors induces in the presence of probenazole in infected host leaves. III. Structural elucidation of substances A and C. Agricultural and Biological Chemistry 47 1983–1989. RICE BLAST CONTROL Michiaki Iwata is a plant pathologist at the Pharmaceutical Research Center of Meiji Seiki Kaishi Ltd.He has been involved in research into the control of plant diseases for 30 years and in particular has extensive experience in the elucidation of plant self-defence systems. 3 1 JAPAN PLANT PROTECTION ASSOCIATION The Japan Plant Protection Association (JPPA) was established in 1953 for the promotion of scientific and technical aspects of crop protection particularly with pesticides as an incorporated body under the supervision of the Ministry of Agriculture Forestry and Fisheries. Membership The membership consists of private individuals supporting members and affiliated prefectural plant protection society members (Japan is divided into 47 prefectures) Organisation The JPPA is composed of 4 divisions (General Affairs Promotion Test and Study and Publication Divisions) and a research institute.The latter operates a research and test farm at Ushiku Ibaraki Prefecture and two test farms at Noichi Kochi Prefecture and at Sadowara Miyazaki Prefecture. Activities Conferences and symposia The JPPA holds annual district plant protection conferences in 6 districts and annual symposia and field observation tours. Research and testing Here work is done firstly on research to develop and improve testing procedures to evaluate the efficacy of candidate products in controlling target pests and diseases to study effects on non-target organisms and carry out environmental fate studies. Publications Plant Protection (Shokubutsu Roueki) – monthly journal in Japanese Agrochemicals Japan – biennial journal in English and a number of books International activites The JPPA hosted the 6th International Congress of Entomology in 1980 the 5th International Congress of Pesticide Chemistry in 1982 and the 5th International Congress of Plant Pathology on 1988 (all in Kyoto). Further information Japan Plant Protection Association (JPPA) 43-11 1-chome Komagome Toshima-ku Tokyo 170 Japan. Tel. +81 (0)3 3944 1561; FAX +81 (0)3 3944 2103 Pesti cide Outlook – Fe b r u a r y 2001

ISSN:0956-1250    

DOI:10.1039/b100805f

出版商:RSC    

年代:2001

数据来源: RSC