摘要:

SUMMARYThree viruses or virus strains were isolated from pawpaw showing field decline symptoms in Tanzania and Kenya, where they are of wide occurrence. Each virus caused a distinct type of local lesion inChenopodium quinoa; a fourth type of local lesion was induced when transmission was from a source containing two of the three viruses. When re‐inoculated to pawpaw, alone or in combination, they caused stunting and decline symptoms similar to those observed in the field.Two were recovered from pawpaw pollen; none was transmitted through seed or from fruit to fruit, nor was any vector found.Purified preparations of the three viruses contained stiff rod‐shaped particles 750 times 12 nm.Latex from pawpaw petiole and fruit totally inhibited sap transmiss

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04596.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYSevere yellowing and stunting was widespread in lettuce crops in Britain in 1968. Cucumber mosaic virus was consistently obtained from affected plants and from weeds which were prevalent in lettuce fields. Infection was most frequent inStellaria mediabut also occurred, more or less commonly, inSenecio vulgaris, Urtica urens, Tripleurospermum maritimumssp.inodorum, Capsella bursa‐pastoris, Lamium purpureumandSonchus oleraceus.Most infected weeds were symptomless. Infected weeds were still common in January‐April 1969 and are considered to be a major overwintering source of the virus for aphid transmission to lett

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04597.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYIn an experiment in which the roots of field‐grown tulip were commonly infected with tobacco necrosis virus (TNV), Augusta disease did not develop in the year of infection or when progeny bulbs were grown in the field or glass‐house. When tulip bulbs of other stocks, including grades of 11 and 12 cm circumference, were forced, the disease developed sporadically, in some instances as the result of infection with TNV from the soil in which they were planted and in others as a result of infection by bulb‐borne virus. The incidence of disease produced by current year infection was increased by warming the plunge bed.Different strains of TNV were obtained from field‐grown plants with Augusta disease and different strains of the virus produced the disease when inoculated to tulip. Some, but not all, naturally diseased plants contained satellite virus, which therefore does not cause or prevent disease development. The disease was produced in some plants by TNV transmitted byOlpidium brassicae,but neither a vector nor a non‐vector isolate ofO. brassicaecompleted its life cycle in tulip. However,Olpidium‐like zoospores were observed in some washings of tulip roots from TNV‐infested soils.TNV was not obtained from all tulip plants with necrotic leaf symptoms resembling Augusta disease. Some were infected with tomato bushy stunt virus or cucumber mosaic virus, or with another agent that was transmitted by inoculation of sap toNicotiana clevelandiiandChenopodium quinoa,and carried by bulbs of up to 11 cm

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04598.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYA routine laboratory method for the detection ofPseudomonas phaseolicolain bean seed is described. The method will detect low levels of seed‐borne infection and has been used in a statistical procedure (the most probable number method) to give an estimate of percentage infection. Infection in seeds harvested from heavily infected crops varied from 10 to 1%, compared with from 1% to less than 0.1% in commercial seed stocks. A high proportion of infected seeds failed to produce infected plants and this may account for the very low levels of primary infection reported in the field. Removal of seeds showing possible ‘symptoms’ of disease reduced, but did not eliminate, infection from seed s

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04599.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYIn three experiments, using laboratory, glasshouse and field tests, seed dressings of benomyl‐1½ (42.4 g) to 2 oz (56.6 g) Benlate 50% w.p. per 28 lb (12.7 kg) of seed‐gave complete control ofAscochytainfection of pea seeds. Mixtures of benomyl and captan and benomyl and thiram were also effective. Carboxin, captan, and thiram used as seed dressings, either singly or in mixtures, did not eliminate the pathogen from peas. Germination, emergence and seedling vigour were not impaired by any dres

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04600.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYIsolates ofV. dahliaefrom strawberry, tested in 1968 against cv. Cambridge Vigour, showed differences in virulence; in cvs Talisman and Cambridge Favourite there were no significant differences between plants that were inoculated and those that were not. Evidence from this experiment, and from an earlier non‐replicated experiment with Cambridge Favourite, in which differences of virulencehadbeen apparent, showed that environmental factors can cause variations in disease development that are of similar magnitude to those attributable to genetic variations in host and parasit

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04601.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYWilt incidence in certain hop cultivars recorded during 15 years of experiments on a plot infested with a virulent strain ofV. albo‐atrum, and over shorter periods on various infested farm sites, was studied by multiple regression analysis in relation to rainfall and soil temperature at various periods during the growing season. In the least‐resistant cultivar, Fuggle, the incidence of wilt was always high, and was independent of rainfall and soil temperature. Wilt incidence in other cultivars showed a negative correlation with mean soil temperature at 20 cm for the period mid‐April to late June; no other single or multiple regression wasconsistentlysignificant. It was concluded that the commonly observed association of high wilt incidence with wet weather in early summer is attributable to low soil temperature rather than to high rai

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04602.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYThe biology and infection‐behaviour of a typical isolate ofPhialophora radicicolaCain have been compared with those of a representative isolate ofOphiobolus graminis(Sacc.) Sacc. Both species can utilize a nitrate source of nitrogen and both require thiamine and biotin for growth on inorganic nitro‐gen; P. radicicola, but notO. graminis, was able to synthesize biotin when grown on asparagine as a nitrogen source. The pH range for good growth ofP. radicicolain nutrient solution was narrower than that forO. graminis, and its growth rate on agar was only one‐third.P. radicicolawas the more active decomposer of cellulose, and its cellulolysis adequacy index was I.66 as com‐pared with a value of 0.33 for0. graminis. In agreement with prediction from Garrett's (I966) hypothesis on the cellulolysis adequacy index, saprophytic survival of P. radicicola in wheat straw was shortened by additional soil nitrogen, which prolongs survival ofO. graminis.P. radicicolawas found to spread ectotrophically over the roots of wheat, oats and barley by runner hyphae indistinguishable from those ofO. graminis,but cortical infection caused no necrosis and no discernible check to growth of the infected cereals, nor any significant decrease in grain yield of inoculated wheat grown to maturity. Pre‐existing infection of wheat roots byP. radicicolaretarded spread of infection byO. graminis; inoculation of several grass species withP. radicicolareduced the extent of infection byO. graminisof wheat following th

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04603.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYTrichoderma viridespores applied in water to apparently uninjured skin of oranges do not cause lesions. Adding orange juice, rind extract, citric acid or orange essential oil did not influence infection. Oranges became infected only when the stem‐end cuts or wounds deeper than 6 mm into oil vesicles were inoculated. Sound oranges in contact with decayed oranges did not become infected. Diphenyl‐impregnated wrappers reduced infection. A mixed inoculum ofT. virideandPenicillium digitatumcaused as fast rotting asP. digitatum, which caused faster rotting thanT. viridealone. Lesions infected withP. digitatumcould become infected byT. viridebut those caused byT. viridedid not become infected byP. digitatum.T. viridewas antagonistic toP. digitatum in vivoandin vitro, possibly because it produces a heat‐labile diffusible substance toxic toP. digi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04604.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYWhen soil was maintained at a mean water potential (Slatyer&Taylor, 1960) of the order of ‐80 J kg‐1at 25 cm depth throughout the growing period, much infection of potato tubers byStreptomyces scabiesoccurred, but when soil was irrigated to maintain it at potentials greater than ‐ 13 J kg‐1at 10 cm depth infection was negligible. Until about 5 weeks after initiation, tubers were very susceptible to infection; irrigation during this period reduced scab considerably, but subsequent irrigation reduced it only slightly.At the low water potential, actinomycete populations on lenticels were high and bacterial populations low; these effects were reversed at the high water potential. Since also actinomycetes were more frequently isolated in the absence than in the presence of bacteria it was deduced that there was an interaction between these two groups. It is suggested that irrigation may decrease the population ofS. scabiesin tuber lenticels by increasing populations of bacteria antagonisti

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04605.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY