摘要:

SUMMARYCarrots that show symptoms of carrot motley dwarf contain two viruses, carrot mottle virus (CMV) and red‐leaf virus (RLV). CMV cannot be manually inoculated to carrot, but can be to some other members of the Umbelliferae, as well as to some species of the Solanaceae, Leguminoseae and Chenopodiaceae. The host range of RLV is limited to the Umbelliferae, and it is not manually transmissible but was transmitted by grafting.Cavariella aegopodiaeScop, transmits RLV alone but will transmit CMV only from plants infected with both viruses. Thus aphids were unable to transmit from coriander plants manually inoculated with CMV, but after these plants were infected with RLV by aphids, virus‐free aphids acquired and transmitted both viruses from them.Aphids remain infective with both viruses for 1–2 weeks, and retain infectivity through the moult. A minimum total of about 9 hr. is needed for acquisition and transmission; vector‐efficiency increases with increasing feeding times up to severaj days.The viruses causing motley dwarf become attenuated in the glasshouse after continued aphid‐transmission; avirulent isolates protect their hosts against infection by virulent ones.Infectivity of saps from CMV infected plants was increased by extraction at high pH in the presence of a trace of Zn, and was associated in carrot with particles 30 mμ in diameter. Water‐phenol extracts are almost as infective as extracts in buffer, but are inactivated by 0·02 μg./l. pancreatic ribonuclease.Parsnip mottle virus (PMV) resembles CMV in many ways, but also differs in some important respects. Unlike CMV it infects celery and parsnip, and it is transmitted byC. pastinacaeas well asC. aegopodiae, the only vector of CMV (in combination with RLV). PMV is transmitted by aphids from plants infected with it alone, whether these plants were infected by aphids or by manual inoculation.Carrot plants infected first with PMV and then with the motley dwarf virus complex developed symptoms of motley dwarf, but in coriander the reverse happened. CMV and PMV appear to interfere with each other's multiplication in the hosts, but CMV is dominant in carrot and PMV in coriander. They have some properties of distantly r

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1964.tb01179.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SUMMARYThe properties and mode of transmission of strawberry latent ringspot virus (SLRV) are described. Natural infections have been found, in several widely separated localities, on cultivated and wild rosaceous species—strawberry, raspberry, cherry, plum, black currant—and on elder (Caprifoliaceae), but so far no diseases in these plants have definitely been associated with SLRV. Similarly, SLRV was transmitted mechanically to a wide range of hosts, many of which it infected symptom‐lessly. SLRV is transmitted byXiphinema diversicaudatum(Micoletsky), has polyhedral‐shaped particles of about 26 mμ diameter, and has other features that suggest it should be classified along with a group of other similar soil‐bor

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1964.tb01180.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SUMMARYBlack‐currant yellows virus restricted the growth of bushes var. Baldwin and Wellington XXX and decreased the total weight of fruit harvested in six seasons by 70%. The size and number of fruits were decreased and in one season ripening was retarded. Virus spread naturally to only four of 250 other bushes in the trial.A strain of reversion virus which caused transitory vein‐pattern symptoms did not restrict vegetative growth, yet decreased the number and size of fruits. In contrast to the more severe effects of prevalent virulent strains, the total crops from the Wellington XXX and Baldwin bushes were decreased by 50 and 33% respectively. The virus spread to fifteen of the 136 healthy bushes and to at least six of the 108 bushes previously infected with yellows virus.The black‐currant gall mite (Phytoptus ribisNal.) increased more rapidly on the Wellington XXX bushes than on those of Baldwin. In each variety the infestation was much greater on reverted than on other bushes, apparently because infection with reversion virus decreased natural resistance to

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1964.tb01181.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SUMMARYA strain of raspberry ringspot virus (RRV‐E) infecting blackberry in Essex was transmitted by inoculation of sap to twenty‐six herbaceous species, and caused symptoms inNicandra physaloides, Datura metelandGomphrena globosathat differentiated it from the Scottish strain of the virus (RRV‐S). In sap, with an infection end‐point of 10‐5, it was inactivated in 10 min. at 74° C, and in 5 weeks at 23° C. It was precipitated without inactivation by a 30% acetone or 30%‐saturated ammonium sulphate solution, but was inactivated when acidified to less than pH 4. Partially purified preparations of RRV‐E contained approximately equal amounts of three components with sedimentation rates of 50, 90 and 127S; electron micrographs of preparations mounted in neutral sodium phosphotungstate showed three kinds of particles with diameters about 30 mμ but with different internal structure. A preparation of RRV‐S contained a main component with a sedimentation rate of 129s, and a minor one with 50S.Petunia hybrida, cucumber and French bean seemed equally susceptible to infection with RRV‐E when grown in soil containing the nematode vectorLongidorus macrosoma, but inoculation of sap infected the roots ofP. hybridamuch more readily than roots of the other two species. Cucumber seedlings became infected when exposed for 1 day to infectiveL. macrosoma, and virus‐freeL. macrosomaacquired the virus from plants in 4 days. InfectiveL. macrosomatransmitted readily at 20° C, occasionally at 25° C, and not at 30° C; feeding seems inhibited at 30° C. RRV‐E was transmitted to seedlings grown in soil containingL. macrosomathat had been kept free from plants for 34 days. Of sixty‐eight extracts of infectiveL. macrosomainoculated toChenopodium quinoapla

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1964.tb01182.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SUMMARYShading retarded the growth of cocoa seedlings infected with cocoa swollen‐shoot virus proportionately more than the growth of uninfected seedlings. Infected seedlings grown in bright light did not produce the swellings on stems and roots which were consistent symptoms of infection on plants grown under shade. The type of leaf symptoms also differed in shaded and unshaded seedlings.Attention is drawn to the possible implications of shade in the severity of swollen‐shoot outbreaks in farmers' co

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1964.tb01183.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SUMMARYAt Mokwa in Northern Nigeria early planting and close spacing increased the yield of groundnuts and decreased rosette incidence. With late planting, increasing the plant population reduced both the rosette incidence and the number of aphid‐infested plants. It is suggested that wingedAphis craccivoraKoch bring the virus into the crop, and that spacing and planting date affect rosette incidence because of the influence of groundcover on the optomotor landing response of the winged aphid

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1964.tb01184.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SUMMARYFour experiments were done under glass in which tomato plants were inoculated with TMV (tomato strains of tobacco mosaic virus) at different times during their growth, and most of the healthy control plants were kept uninfected throughout the season. Leaf symptoms were visible 2–3 weeks after inoculation, and infected plants were checked and grew more slowly than healthy ones. Leaves of infected plants were sometimes scorched by overhead damping with water, and lower leaves died earlier than those of healthy plants.In the 1960 experiment, with a winter‐sown crop, plants inoculated on 3 March, when the first trusses began to flower, suffered a 15% loss in weight of fruit; those inoculated on 14 April, when the fifth trusses began to flower, an 18% loss, and those inoculated on 31 May, when most of the fruits had set, a 14% loss. The two early infections caused 13% fewer fruits to set, but the last one only 3% fewer; however, with successively later infection dates, mean fruit size progressively decreased. Fruit quality was severely affected by later infection, 10% of the fruits from plants infected in April showing necrotic pitting, bronzing or severe mottle, but 31% of those infected on 31 May.Three experiments with spring‐sown plants gave similar results. In the 1961 experiment, plants inoculated on 3 May, when the first trusses began to flower, yielded 21% less weight of fruit than the controls, and those inoculated on 8 June, when the fifth trusses began to flower, 14% less. A tobacco strain of TMV that caused no symptoms in tomato failed to protect plants from later infection with a tomato strain. In the 1962 experiment, seedlings inoculated on 13 March, just after pricking out, yielded 10% less weight of fruit; plants inoculated on 4 April, just after planting out, 3% less; those inoculated on 3 May, when the first trusses began to flower, 11% less; and those inoculated on 7 June, when the fifth trusses began to flower, 16% less. In the 1963 experiment, plants inoculated on 21 May, when the first trusses began to flower, yielded 17% less weight of fruit than the controls, and those inoculated on 20 June, when the fifth trusses began to flower, yielded 23% less; many of the control plants became infected during August in this last experiment. As in the first experiment, losses were largely due to poor setting of fruits at the time the plants became systemically infected with virus, and necrotic pitting and severe bronzing again mainly affected fruits from the late‐infected plants. The plants grew vigorously and were ‘soft’ or lush in all the four

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1964.tb01185.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SUMMARYIn the seedling method of inoculation of barley withUstilago nuda, a chlamydospore suspension is introduced into decapitated coleoptiles held under partial vacuum. The optimum conditions for infection were provided by the use of a partial vacuum of 25 in. of mercury for 2 min. on coleoptiles 1‐1·5 cm. long: lower infection percentages resulted when the coleoptiles were over 1·5 cm. No benefit was obtained by suspending the spores in dextrose or peptone solutions.The variety Jet remained immune to infect

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1964.tb01186.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SUMMARYSclerotia ofRhizoctonia solanisurvived for long periods in the laboratory. When left undisturbed in the soil, 79% of buried sclerotia survived for a period of 6 months. Sclerotia retained their infectivity towards seedling wheat plants throughout all viability tests.Sclerotia germinated readily in response to various stimuli and were able to regerminate at least ten times: it is considered that this property enhances their survival value.Although wheat stem isolates decomposed cellulose in pure culture and competitively colonized certain types of cellulose in soil, they were ineffective in colonizing cereal straws in the soil. The pathogen quickly died out in artificially infested soil and showed only limited survival in naturally infected cereal straw buried in soil. In pot experiments the pathogen persisted parasitically under a number of crops.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1964.tb01187.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

SUMMARYLaboratory methods are described for testing soil insecticides against wireworms, and the results obtained with some organophosphorus and carbamate compounds tried as possible alternatives to chlorinated hydrocarbons are reported. The most promising compounds in the laboratory tests were thionazin,O‐ethylS‐p‐tolylethylphosphonodithioate (Bayer 38156) and fenthion. These were tested in a small‐plot field trial with cereals, on land severely infested with wireworms: the compounds were applied to the soil as sprays at 2·7 lb./acre active ingredient before the crop was drilled. Fenthion was ineffective, but thionazin and Bayer 38156 each increased yields significantly and the increases were associated with diminished wireworm pop

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1964.tb01188.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY