摘要:

SUMMARYA tomato strain of tobacco mosaic virus infected, on average, about half the cleaned seeds from infected fruits. The proportion differed with tomato cultivar, time of infection and truss. Virus content also varied; seeds usually carried TMV externally, in low concentrations, but about a quarter also carried it within the testa or the endosperm. High virus concentrations sometimes occurred internally, usually when the endosperm was infected. Internal infection decreased, mainly by absence of virus in the testa, as the plant age at the time of infection increased. Endosperm infection occurred mainly in fruits from flowers that set after the plants were infected. The proportion of fruits with seeds was smaller in early infected plants than in those infected later. Fewer necrotic, blackened seeds were obtained from late‐infected plants than from those infected earlier, and more necrotic seeds were infected with TMV than normal ones, especially in the endosperm. Although the embryo was sometimes contaminated during dissection, virus within it was never confirmed. Necrotic seeds often failed to germinate.Treating the fruit pulp with one‐quarter of its volume of conc. hydrochloric acid for 30 min. was the best means of cleaning seeds and of eliminating TMV carried externally. Fermentation and sodium carbonate extraction did not eliminate external TMV. Soaking previously cleaned seeds in 10% Teepol (Shell non‐ionic detergent) solution for 2 hr., or in a 10% tri‐sodium orthophosphate solution for 20 min. also inactivated external virus. The only treatment that often eliminated TMV carried internally was heating dry seeds in an oven at 70d̀C; treatment for 3 days was usually enough to free seeds completely but sometimes 3 weeks would not eliminate all virus, particularly that carried by the endosperm. Such treatments did not affect percentage germination of seeds other than recently harvested ones, but heated seeds sometimes took longer to germinate than unheated ones.TMV was lost within a few months in some stocks of seeds but persisted for at least 9 years in others with endosperm infection. Virus content of seeds fell rapidly for 2 weeks after sowing but then remained at a low level for many weeks. Plants never became infected when allowed to grow undisturbed after the seeds were sown. ‘Seed‐infectio’ occurred only when the seedlings were pricked out (transplanted) and the testas or remaining endosperm were rubbed against the seedlings. The proportion of plants thus infected was usually small because (1) many seeds did not carry virus; (2) virus was rapidly inactivated after sowing; (3) after normal sowing 65% of testas were left behind in the soil when the seedlings were pricked out; (4) very young seedlings resisted infection: and (5) infection was more likely with recently harvested than with older seeds, probably from TMV remaining on the testas. However, all seedlings which were infected, even with dilutions of TMV‐infected leaf sap leaf in water as low as one part in five millions, showed symptoms

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb01227.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYThe viruses causing two tomato leaf‐curl diseases, tomato leaf curl without vein thickening (TLCV) and tomato leaf curl with vein thickening (TVTV), were both transmissible (to tomato and other hosts) by the aleurodidBemisia tabaci(=B. gossypiperdaM.&L.) and by grafting, but not by mechanical inoculation of expressed sap. A third virus, which arrested growth of the shoot apices and caused a disease referred to as tomato condensed top (CT), was transmissible only by grafting and was not studied in detail.Both TLCV and TVTV belong to the complex of tobacco leaf‐curl viruses described by other workers, but the different effects of the two and their failure to interfere with one another in plants suggest that they are not strains of one virus.TLCV and TVTV were not transmissible to cotton nor was cotton leafcurl virus transmissible to tobacco, tomato orDatura stramoniumL. Virus transmitted from okra with leaf curl caused leaf curl both in cotton and tobacco, suggesting that the okra was infected with a mixture of viruses or with a virus having a new combination of properties. TVTV was transmitted with difficulty to okra, causing vein thicken

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb01228.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYCuttings from fifty T17 seedling trees derived from an open‐pollinated pod from the Iquitos selection no. 53 were each infested with fifty infective mealybugs (Planococcus njalensis) carrying either the severe New Juaben strain of cocoa swollen shoot virus or the Kpeve strain of cocoa mottle leaf virus.All but forty‐seven out of 1000 cuttings treated with CSSV became infected. All Amelonado beans treated at the same time as these cuttings with thirty insects each became infected. There was no evidence of variation in susceptibility to infection with CSSV in the T17 progeny. The infected plants were scored for tolerance; one clone seemed more tolerant and five less tolerant than the remainder. Deposition of mixed pollen in the natural pollination is suggested as the cause of this variation in tolerance in the progeny. There was no evidence of rcsistance and tolerance being associated. Tolerance to CSSV was much higher in the T17 progeny than in Amelonado.Transmission rates of CMLV were much lower than of CSSV both to the T17 cuttings and to the Amelonado beans, Conditions at the time of infestation clearly affected the transmission rates. No evidence of variation in susceptibility to infection with CMLV was found in the T17 progeny. Plants infected with CMLV were scored for tolerance in only one replicate; there was little evidence of variation and none of an association between resistance and tolera

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb01229.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYCuttings of twenty‐seven cocoa selections were infested with mealybugs (Planococcus njalensis) which had fed on plants infected with the New Juaben strain of cocoa swollen shoot virus. Susceptibility to infection with CSSV seemed to vary, and in general those selections which had appeared relatively resistant in earlier studies again appeared resistant. There were great differences in reaction to infection, clones from Scavina × unknown progenies being least affected while various other Amazon selections, particularly some from Iquitos × unknown and Nanay × Iquitos progenies, were also very tolerant. Some local Trinitario selections displayed a measure of tolerance. The tolerance results were similar to those previously obtained in Ghana with the same virus and using beans or seedlings, and also to those obtained in field trials and with budded material infected with Nigerian virus isol

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb01230.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYIn 1963 and 1964 single sugar‐beet plants (infectors) growing in commercial root crops were infected with either beet yellows virus (BYV), beet mild yellowing virus (BMYV), or both viruses, by viruliferousMyzus persicae(Sulz.). Virus‐free aphids were put on other beet plants. All theM. persicaewere then removed, but in 1964 additional ones, either virus‐free or viruliferous, were put on half the plots. More plants subsequently became infected with yellows viruses in plots containing infectors than in those without.In 1963 more virus spread from BYV than from BMYV infectors; in 1964 the reverse happened. Usually less of either virus spread from plants with dual infection than from those singly infected. In 1964 more virus spread in plots where additional viruliferous apterae ofM. persicaewere set free on infector plants than in others where the aphids were removed.The greater spread of BYV than of BMYV in 1963 is attributed to transmission byAphis fabaeScop., which was exceptionally abundant.The greater spread of BMYV than of BYV in 1964 is attributed to differences in the virus‐vector relationships of the two viruses when transmitted byM. persi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb01231.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYAn apparatus for heating small quantities of soil with steam/air mixtures, at temperatures from 50 to 100d̀ C., is described.Heating naturally infested soils at 60d̀ C. for 10–30 min. eliminated attack byRhizoctonia solaniKuhn and pathogens causing brown root rot, so increasing survival and growth of lettuce and tomato seedlings respectively.Growth in soils heated at temperatures above 80d̀ C. was often less, however, than in soils heated at 60–75d̀ C. Decreases were associated with relatively high soil concentrations of (1) soluble and exchangeable manganese and (2) nitrite. Amounts of ammonia were greatly increased at 52d̀ C., compared with the unheated controls, but those of manganese (water‐soluble and exchangeable) and nitrite were not significantly increased at temperatures less than 65d̀ C.The damage done to lettuce byR. solaniwhen inoculated to preheated soils usually increased with increasing treatment temperatures. Fewer seedlings survived in soils preheated at 60d̀ C. than in the unheated controls but usually more than in soils preheate

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb01232.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYIn studies of the behaviour of sclerotia ofSclerotinia trifoliorum, S. sclerotiorum, Sclerotium delphiniiandS. rolfsiiit was established thatS. trifoliorumandS. sclerotiorumformed apothecia in the field,S. sclerotiorummainly in spring andS. trifoliorumalmost exclusively in autumn. Apothecia were formed from sclerotia down to 2 in. in the soil, the number diminishing with increasing depth. At 6 in., sclerotia developed apothecial stipes up to 21/2 in. long: this limitation was not due to exhaustion of the food reserves of the sclerotia.InS. trifoliorum, apothecial formation was abundant in August, then steadily declined, and ceased in November. Broad red clover was exceptional in stimulating the initial flush in bothS. trifoliorumandS. sclerotiorum, but very few apothecia formed subsequently.Mycelial growth from sclerotia ofS. trifoliorumandS. sclerotiorumwas much sparser, even in sterilized soil, than that from sclerotia ofSclerotium delphiniiandS. rolfsii.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb01233.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYThe survival in soil of sclerotia ofSclerotinia trifoliorum, S. sclerotiorum, Sclerotium delphiniiandS. rolfiiwas studied. Those ofS. rolfsiidisintegrated in less than 1 month, while 95% of those of S.delphiniiandSclerotinia sclerotiorumwere recovered after 2 years.Sclerotia ofS. trifoliorumplaced in soil in March slowly diminished in numbers over the summer months, and in late autumn there was a rapid decrease in those near the surface, as a consequence of apothecial formation. This rapid fall did not occur when sclerotia were buried under clover. Over the winter, sclerotia 1 and 2 in. deep increased in numbers by the formation of secondary sclerotia. Secondary sclerotia also occurred in samples ofSclerotinia sclerotiorum.Soil moisture content affected sclerotial survival, an accelerating decline in numbers being noted up to a soil moisture‐holding capacity of 30%. Above this level, increasing numbers of secondary sclerotia were formed, so that the numbers of sclerotia recovered were sometimes greater than those originally buried.Sclerotia became more liable to decay after producing apothecia, but they did not invariably disappear, and some were capable of forming two or possibly three crops of apothecia in successive year

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb01234.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYPrevious work showed that germ‐tube growth ofBotrytis cinerea, but not ofB. fabae, is inhibited several hours after germination on the leaves. This study concerns the detection of substances in leaves and pods which could explain the different responses of the two fungi.Ether and methanol extracts of leaf surfaces were not inhibitory to either fungus. Drops of water which were incubated for periods up to 48 hr. on healthy leaf surfaces became slightly inhibitory to germ‐tube growth of both fungi. However, drops of water containing spores ofB. cinereabecame highly inhibitory after incubation on surfaces of leaves or in seed cavities of pods for 72 or 24 hr. respectively. Drops containing spores ofB. fabaeand water controls became stimulatory to test spores after incubation for 24 hr. in pods but slightly inhibitory after 72 hr. on leaves. The inhibitory substances were partially extracted from collected drops into petroleum ether. Substances soluble in petroleum ether extracted from the endocarp of pods were highly inhibitory to test spores 24 hr. after infection byB. cinereabut stimulatory before infection or 24 hr. after infection byB. fa

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb01235.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYThe ascospore productivity of severely scabbed apple leaves was reduced by 93.7–99.9% by a single autumn application of phenylmercuric chloride (PMC) over a concentration range of 0.0025–0.1%. Phenylmercury dimethyl‐dithiocarbamate (PMD) was slightly less effective at equivalent concentrations of mercury. Of the non‐mercury compounds tested, only high concentrations of didecyldimethylammonium bromide and the herbicide diuron approached PMC in effectiveness. Low concentrations of PMC applied in the spring reduced the numbers of ascospores released from leaves bearing mature perithecia.A new technique for estimating the ascospore productivity of overwintered apple leaves is de

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb01236.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY