摘要:

The effect ofNysius huttoniWhite feeding on immature plant seeds was examined by caging the insect with the seed heads of the following plants: wireweed(Polygonum aviculare),twin cress(Coronopus didymus),yarrow(Achillea mille‐folium),fathen(Chenopodium album),and native wheat grass. The largest seeds (wheat grass and wireweed) were the most physically damaged with shrivelling and colour changes. The amount of N.huttoniproteinases in infested seeds varied widely from 48 enzyme units/g wireweed seed to 8075 enzyme units/g yarrow seed, but there appeared to be no relationship between proteinase content and the amount of physical damage to the seeds. Sodium dodecyl sulphate (SDS)‐polyacrylamide gel electro‐phoresis showed that high levels of proteinase in twin cress and yarrow seeds could hydrolyse protein subunits of a wide range of molecular weights. In contrast, incubation of undamaged twin cress and yarrow seeds with proteinase purified fromN.Wtom‐damaged wheat grain, did not hydrolyse any protein. The purified enzyme only hydrolysed high molecular weight (HMW) protein subunits in wheat‐grass seeds and wheat grain(Triticum aestivum),and possibly protein macropolymers in giant Spaniard(Aciphylla scott‐thomsonii)and koromiko{Hebe salicifolia)seeds. These HMW proteins in wheat grass, giant Spaniard, and koromiko seeds may have similar structure to the HMW glutenin subunits of wheat grain. We conclude that whenN. huttonifeeds on some seeds it can inject proteinases of a broader specificity range than the highly specific proteinase found inN. huttoni‐damagsdwheat, and we suggest that particularly the latter enzyme has a role in softening the outer layers of seeds to facilitate bug stylus penetration and maintain the flow of sap.

ISSN:0114-0671    

DOI:10.1080/01140671.1999.9514096

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Cucumber mosaic virus (CMV) has been detected in lentil(Lens culinarisL.) seed grown in New Zealand. In 1994 experimental plots of lentil plants ‘Rajah’ inoculated with CMV yielded 15% less seed than uninoculated. In 1995, seed losses were similar for ‘Rajah’ and ‘Titore’, but losses were greater at 17 and 19%, respectively. Plant numbers were also reduced by CMV infection—by 18% in ‘Rajah’ and 7% in ‘Titore’. Thousand seed weight was not affected by infection. Surveys of commercial lentil seed lines detected CMV incidences of between 0.05 and 2.5%. In a field experiment in 1996, using four levels of seed‐borne CMV (0, 0.5, 1, and 2%) obtained by blending infected and healthy seed, mean seed‐borne incidences in harvested material of between 1.5 and 6% were recorded. No reductions in seed weight or subsequent germination rate were recorded. Plant numbers were slightly reduced by seed‐borne CMV. Transmission of CMV from infected seed was measured. A linear relationship was observed from 1% transmission in plots sown with clean seed to 4.9% transmission in plots sown with seed having a 2% level of infection.

ISSN:0114-0671    

DOI:10.1080/01140671.1999.9514097

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The infection process byBotrytis cinereaPers. on lemon fruits (Citrus Union(L.) Burm.), and development of rind distortion are described. Infections occur on juvenile fruitlets soon after petal fall from hyphae growing over the surface of the fruit from adjacent colonised flower debris. The hyphae form compact infection cushions at their tips. There is a collapse of epidermal cells and several layers of underlying cells in the vicinity of the infection cushion, leading to the formation of small necrotic pits on the surface of the fruit. As the fruitlets grow, there is generalised hyperplasia in a zone up to 20 cell layers deep in the region of the necrotic pits, leading to conspicuous outgrowths on the fruit surface. The initial wound becomes stretched, flattened, and corky as the fruit enlarges. A cambial layer is located below the area of damaged tissue, fluorescence in the vicinity of the cork cambium indicates the presence of suberin in the cambium. There was no evidence of suberin or lignin deposition in the region of the original necrotic pit. The necrotic pits are characteristic of a non‐pathogenic reaction between the fungus and the host, with fungal hyphae failing to become established in the necrotic tissues of the pit. The hyperplasia leading to the rind distortions is considered to be a generalised reaction to the initial wound and is commonly observed in lemon following other types of injury to the rind. The principal sources of inoculum in orchards areBotrytis‐colonised floral debris caught up in flower clusters or adhering directly to the fruit surface. The etiology of the disorder helps explain why control by conventional fungicides is seldom successful. Not only are there physical limitations to providing a protective cover on very small fruit, but also the extended period over which flowering occurs in lemon imposes limits on the number of applications able to be economically applied. In the absence of effective control systems, growers are advised to modify husbandry practices such as lowering the density of shelter belts, opening lemon canopies to assist drying out of the flowers, and use of air blast orchard sprayers to physically remove floral debris from the vicinity of young fruit.

ISSN:0114-0671    

DOI:10.1080/01140671.1999.9514098

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The patterns of fungal infection and mycotoxin contamination in leaf and ear sections of plants of two maize(Zea maysL.) hybrids, one resistant to mycotoxin accumulation under New Zealand conditions (Pioneer 3902 (P3902)) and one less so (Pioneer 3751 (P3751)), have been measured. Sampling commenced early in the season, well before ear and tassel formation, and continued until harvest. A number of fungi were isolated, the most common overall beingFusarium.Most common in leaf fractions wereEpicoccum, Fusarium,andAlter‐naria,whereas in ear fractions the most common wereFusarium, Penicillium, Cladosporium,andMucor.The most common fusaria isolated from leaf fractions were the toxigenic speciesF. crookwellenseandF. graminearum.These species were evident from late February although other, non‐toxigenic, species were present in leaf axils from early January. For ear fractions the most common species wereF. graminearum, F. crookwellense,andF. subglutinans. Fusariuminfection was evident in ears of P3902 from March to April, although heavy infection by the toxigenic species tended to occur later towards May‐June, especially for the basal ear fractions. For P3751 ear infection commenced in May, and then was predominantly by toxigenic species. Mycotoxins were found in most plant fractions measured, especially as the plants aged. The toxins found reflected the particular toxigenicFusariumspecies present in the fraction. The highest mycotoxin concentration in a leaf fraction was 16.6 mg/ kg of zearalenone (ZEN) in an upper leaf axil sample. Nivalenol (NIV) was also found at up to 7.4 mg/ kg in leaf axils. The most contaminated ear fraction was the rachis, with over 40–95 mg/kg of ZEN, NIV, or deoxynivalenol (DON) at various times. The highest concentration found in kernels was 3.8 mg/kg of DON found in apical kernels of P3751 two weeks before harvest. The results suggest that the mechanisms of maize infection byFusariumin New Zealand may not be controlled by factors at silk emergence but rather by later season events such as high rainfall and warmer temperatures.

ISSN:0114-0671    

DOI:10.1080/01140671.1999.9514099

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

In a commercial orchard, mature trees of the almond(Prunus dulcis(Mill.) D. Webb) cultivar ‘Butte’ propagated on peach(P. persica(L.) Batsch) seedlings exhibited delayed budbreak in spring, sparse foliage, poor shoot growth, and produced shriveled kernels. Extracts of leaf petioles from diseased, but not healthy, ‘Butte’ trees were positive by dot‐blot hybridisation assays for the presence of a phytoplasma. In addition, diseased almond buds were graft‐inoculated onto the ‘Peerless’ almond propagated on ‘Marianna 2624’ plum rootstock and induced brown line and pitting at the rootstock/ cultivar union, a condition associated with peach yellow leaf roll phytoplasma (PYLR‐phytoplasma) infection in this indicator host. Furthermore, buds of peach infected with PYLR‐phytoplasma induced similar canopy and kernel symptoms when bud‐inoculated onto previously healthy trees of the almond cultivars ‘Peerless’ and ‘Nonpareil’ propagated on peach seedlings. However, a ‘Peerless’ tree infected with X‐disease phytoplasma appeared unaffected. Ilarvirus and dsRNA analyses of diseased ‘Butte’ trees were negative. Diseased trees treated with oxy‐tetracycline caused remission of symptoms. These results indicate that infections by a phytoplasma, specifically PYLR‐phytoplasma, are responsible for kernel shrivel symptoms in almond trees grown on peach seedlings.

ISSN:0114-0671    

DOI:10.1080/01140671.1999.9514100

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Sweet pepper (Capsicum annuumL.) plants were grown using Nutrient Film Technique (NFT) system with a nutrient solution of electrical conductivity (EC) 2 mS cm‐1. Higher conductivity levels of 4, 6, 8, and 10 mS cm‐1were achieved by adding concentrated KC1 solution to the basic nutrient solution. Higher ionic strength of the nutrient solution resulted in smaller sized fruit, reduced fruit dry weights, and decreased vegetative growth in terms of lower leaf area and specific leaf area (SLA). It also encouraged accumulation of more assimilates in shoots than fruits, decreased plant water consumption, leaf ψ, and fruit firmness. It increased leaf sto‐matal resistance, fruit dry matter content, fruit respiration and ethylene production, and advanced fruit colour change.

ISSN:0114-0671    

DOI:10.1080/01140671.1999.9514101

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Sweet pepper(Capsicum annuumL.) plants were grown using Nutrient Film Technique (NFT) at electrical conductivity (EC) levels of 2 ,4, 6, 8, and 10 mS cm‐1. Higher EC levels were achieved by adding concentrated KC1 solution to the basic nutrient solution maintained at EC 2 mS cm‐1. An additional treatment of high Ca with EC 10 mS cm‐1was made up of a solution of KC1 and CaCl2at a ratio of 3:1 (w/w). High nutrient conductivities resulted in high blossom‐end rot (BER) incidence. This was related to the suppression of Ca uptake and reduced accumulation in the fruit accompanied by an increase in the accumulation of Mg and particularly K. Extra Ca at the highest EC level promoted the accumulation of Ca by the fruit and reduced the incidence of BER. The reduction of Ca uptake in the fruit at higher EC was more pronounced at the blossom‐end of the fruit. Fractionation of Ca compounds revealed that higher EC levels reduced the physiologically active acetic acid soluble component, particularly during the BER sensitive rapid fruit growth stage.

ISSN:0114-0671    

DOI:10.1080/01140671.1999.9514102

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The phenological development of one variety of chickpea(Cicer arietinumL. ‘Hernandez') was studied in Canterbury, New Zealand using eight sowing dates in 1992–93 (July and September), 1993–94 (July until November), and 1994–95 (October). The duration of all phases was predicted based on thermal time above 4°C. For emergence to flowering (E‐F), photoperiod‐corrected thermal time with a base photoperiod of 10 h was calculated, but thermal time gave a better relationship with flowering rate. The mean accumulated thermal times for the different phases were 133, 447, 761, and 377°C days for sowing to emergence (S‐E), E‐F, flowering to mature pod (F‐MP), and mature pod to harvest maturity (MP‐HM) respectively. An accurate prediction of time to flowering was made based on an accumulated mean thermal time requirement of 447°C days from E to F. The relationship between the actual and predicted dates of flowering was highly significant(r2=0.983), and data from an independent source fitted the model well.

ISSN:0114-0671    

DOI:10.1080/01140671.1999.9514103

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This study was initiated to evaluate the chemical properties in terms of fatty acid compositional changes in developing persimmon(Diospyros lotusL.) fruits. Seven stages of fruit development (days of year, DOY) were chosen beginning from fully green to fully yellow. The fruits were collected between 201 and 320 DOY. In the fruit, 11 fatty acids were identified and quantified: myristic acid (14:0), palmitic acid (16:0), palmitoleic acid (16:1), stearic acid (18:0), oleic acid (18:1), li‐noleic acid (18:2), linolenic acid (18:3), arachidic acid (20:0), behenic acid (22:0), lignoceric acid (24:0), and pentacosanoic acid (26:0). Four acids: palmitic acid (16:0), palmitoleic acid (16:1), linoleic acid (18:2), and linolenic acid (18:3) were identified as the major acids in significant amounts(P= 0.05) during development. The highest levels of these four acids were found at 251 DOY whereas the levels of these acids began to decrease between 273 and 320 DOY. However, a sharp decrease in the level of 14:0 acid was seen at 273 DOY, and then the level increased at 290 DOY. Between 290 and 320 DOY the level of the acid remained constant. Another four fatty acids: arachidic acid (20:0), behenic acid (22:0), lignoceric acid (24:0), and pentacosanoic acid (26:0), did not show the same increases or decreases in during development, but the levels were found to be significantly important in some stages.

ISSN:0114-0671    

DOI:10.1080/01140671.1999.9514104

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:0114-0671    

DOI:10.1080/01140671.1999.9514105

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor