ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1979.tb02220.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractMost well–known laboratory methods which can be used in the diagnosis of fireblight, as well as more recent developments in identification, have been discussed. They vary from the use of simple culture media to the use of immunofluorescent microscopy. The use of any one method alone is not advised, but by combining methods, accurate and rapid diagnosis is possible. In order to minimize diagnostic errors, especially among less experienced workers, the use of 5 % sucrose–nutrient agar for bacterial isolation followed by serological control is recommended. For further information reference is given particularly to the procedures described by Lelliott at the first EPPO Conference on Fireblight held in 1967 at Canterb

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1979.tb02221.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractUnderstanding the disease cycle of fireblight requires knowledge of the sources of inoculum and means of dissemination. In regions where the disease is endemic, hold–over cankers are the most important source of primary inoculum. Dissemination of primary inoculum occurs by rain or by crawling or flying insects. Often, blossoms infested withErwinia atnylovora(Burrill) Winslow et al. provide secondary inoculum that is disseminated by pollinating insects or by rain. Later in the growing season, secondary inoculum produced in infected tissues may be disseminated by rain or by sucking and biting insects. Relatively rare sources of inoculum and inefficient means of dissemination may be responsible for introducing the pathogen to areas where fireblight has not been found previously.E. amylovoramay be carried to new locations in intimate association with host tissues (infected nursery stock), in association with vectors (insects, birds or man), or by wind as “strands” or in airborne water drops. Every effort should be made to prevent introduction ofE. amylovorainto areas now thought to be free of fireblight. Attempts to eradicate the disease from several new areas in northern Europe have been unsuccessful. Because weather conditions and the host plants present in southern Europe are especially conducive to severe damage from fireblight, plant protection personnel are advised to prepare now for the possible introduction of disease. Personnel should be trained to recognize the disease and plans should be drawn to contain it or to manage host plants to minimize disease l

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1979.tb02222.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractResistance in apple is evaluated by needle–inoculation of succulent shoot tips with 106–107cells of a virulent isolate ofErwinia amylovora(Burr.) Winslow et al. (the incitant of fireblight) and measurement of the resulting cortical lesion when extension is complete. Data are now available on practically all commercial cultivars, some of which have a useful level of resistance. Some newer cultivars, particularly those with resistance to scab (Venluria inaequalis[Cooke] Wint.) derived fromMalus floribunda, have good resistance toE. amylovora. Avery high level of resistance is present in AsiaticMalusspecies, includingM.xrobusta, M.xsublo–bata, M.xatrosanguinea, andM. prunifolia, and in the North American speciesM. fusca.This type of resistance appears to be inherited polygenically, and because of its detectability in young seedlings can be used conveniently in breeding.Objectives of pear breeding programs are aimed at developing superior fruit quality combined with resistance to fireblight, psylla, andFabraealeaf spot. Many high quality cultivars ofPyrus communisare extremely susceptible toE. amylovoraand sensitivity appears to be controlled by a dominant gene Se. A high level of resistance is present inP. ussuriensisbut varies considerably between clonal selections of otherPyrusspecies. Pear seedlings from controlled pollinations are artificially inoculated in the glasshouse with a similar bacterial suspension as used for apples, and only the most resistant ones are selected and planted in the field for future evaluation. In Beltsville, heritability studies of crosses between non–sensitive parents have indicated that selection for resistance within progenies results in a high degree of genetic gain. Interspecific hybridization has an advantage overP. communiscrosses mainly when insect or fungus resistance is r

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1979.tb02223.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractHeritability studies in ornamentals with regard toErwinia amylovora(Burrill) Winslow et al. were started shortly after the introduction of the pathogen into northern Europe. Since that time, approximately 8,000 plants from 17 genera of Rosaceae have been tested; 7 genera were reported to be susceptible: the economically importantCotoneaster, Crataegus, Cydonia, Pyracantha, Sorbus, and, in addition,ChaenomelesandStranvaesia.Moreover, 9,000Cotoneasterseedlings comprising 15 cultivars were tested and the surviving individuals used for breeding purposes. The variation between these first results reported in the different European countries and some American findings is considerable because of different inoculation procedures and various epidemiological conditions. However, resistance sources have been identified and it would be desirable to start co–operation in this field on an international leve

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1979.tb02224.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractThe ideal warning system should indicate conditions favouring inoculum production and dissemination, infection and subsequent symptom expression. It should give guidance on the best times for inspections to be made and for chemical control measures to be applied. The choice of system is governed by the crop, the climate and economic considerations. New systems must be developed to deal with new situations. Most previous systems have been concerned with the spring blossom periods of pear and apple, but systems for assessing fireblight activity at other times in the growing season are being developed. This is especially important in Europe where the blossom periods of susceptible ornamental hosts extend into July and where, in some countries, summer blossom on pear may be present throughout the season. Monitoring of inoculum levels on cankers, blossoms or shoots has proved valuable where economy in the use of sprays has justified its use; sprays are usually withheld until the pathogen is detected.Warning systems based on weather data are broadly in agreement but differ in detail. Sprays during bloom are often withheld until maximum temperatures exceed 18° C (or mean temperatures reach 14.5 —‐ 16.5° C) and there is precipitation or high humidity (>60 % RH) at the same time. Some workers would spray immediately after moderate rain (e.g. 2.5 – 5.0 mm) when inoculum was known to be present. Spray applications immediately after damaging storms are the general rule. Proper evaluation of warning systems is difficult and is only possible in areas where fireblight is endemic and where adequate field records can be o

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1979.tb02225.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

AbstractA review is given of the possible measures against fireblight in countries which so far do not have the disease (the “have–nots”) and in countries which do (the “haves”).In the “have–nots”, precautions can be taken by putting into practice our knowledge of susceptibility and sensitivity of host plants in non–commercial as well as in commercial plantations. Some guidelines are given. Planting of the most susceptible non–commercial host plants should be avoided whilst testing and breeding programs for resistance should be stimulated.In the “haves”, an attempt should first be made to eradicate the disease. Some remarks are made about this point. When eradication has proved to be impossible, special attention should be given to the health of the source material for nurseries. This point is worked out in some detail. Also in the “haves”, preventive measures can and should be taken, inside and outside nurseries and orchards. These measures are specified. In cases where infection is found, the foci should be destroyed as soon as possible, without exception in nurseries and orchards, and preferably also outside these holdings. A number of remarks about this point are made.Only by practising an integrated policy by a combination of the measures mentioned can one achieve a maximum of control and a minimu

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1979.tb02226.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1979.tb02227.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1979.tb02228.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

ISSN:0250-8052    

DOI:10.1111/j.1365-2338.1979.tb02230.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY