摘要:

When potato tubers were stored at 37‐5°C. in a humid atmosphere, some lost their germinating power after 20 days but others survived up to 40 days. All tubers infected with leaf‐roll virus that survived 25 days at this temperature produced healthy plants. Similar treatments up to 40 days did not free tubers from potato virusesX

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1950.tb00959.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

Pea mosaic virus was transmitted byMyzus persicaeSulz.,Macrosiphum pisiKalt.,M. solanifoliiAsh. andAphis fabaeScop., but not byHyperomyzus staphyleaeKoch. It is a ‘non‐persistent’ virus (Watson&Roberts, 1939), and is most readily transmitted when vectors are fasted and then given a short infection feeding. Vector efficiency was not increased by increases in preliminary fasting beyond 15 min. or with increasing infection feeding beyond 1 hr. Most aphids became non‐infective within 15 min. when feeding, but fasting aphids remained infective for 3 hr. Species that fed readily on the infected plants were less efficient vectors than those which did not. Seed set by infected plants produced healthy seedlings.Pea enation mosaic virus persisted inMyzus persicaeandMacrosiphum pisifor more than 140 hr.; its transmission was unaffected by preliminary treatments of aphids. No transmission was obtained until at least 4 hr. after aphids had left infected plants; usually the ‘latent’ period exceeded 1 day and its duration was apparently unaffected by the length of the infect

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1950.tb00960.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

Young potato plants in pots exposed in the open near plots of potatoes for limited periods at intervals during the summer, became infested with large numbers of winged aphids only during warm, calm and dry weather. Although visited by aphids during May and June, when much of the spread of viruses occurred in nearby potato crops, few of the potted plants became infected. Most potted plants became infected in July when alate aphids were leaving neighbouring potato crops. Widely different proportions of the exposed plants became infected in different years; in two of the three years, many more plants were infected with virusYthan with leaf roll virus.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1950.tb00961.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

Increasing the number ofPseudococcus njalensisper test plant increased the infection rate with cacao virus 1A and 1M to 95 % with twenty‐five insects. Young leaves with the red vein‐banding symptoms were better sources of virus than mature leaves, and there was evidence of virus localization in the plant. It was estimated thatPs. njalensisnymphs took about 16 min. to penetrate plant tissues with their stylets.Infection rates increased with time of test feeding up to 50 min. The virus was non‐persistent in the feeding insect, but persisted up to 36 hr. in insects starved after the infection feed. Starvation before the infection feed increased the infection rate with infection feeds up to 10 hrs., after which the infection rate with pre‐starved insects declined to the level attained by unstarved

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1950.tb00962.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

Thirteen species in the Coccoidea were tested as vectors of seventeen cacao viruses or virus strains; in addition to the vectors previously recorded, the following species transmitted some of the viruses:Paraputo ritchieiLaing,Phenacocctissp. H 6418 (? sp.nov.)PseudococcusbukobensisLaing,Ps. brevipes(Ckll.),Pseudococcussp. nearcelt isStrickland,Pseudococcussp. neargahaniGreen,Ps. longispinusT.‐T. andPseudo‐coccussp. nearmasakensisJames. The viruses transmitted byPs. longispinuswere not usually transmitted byFerrisia virgata(Ckll.), but there was no other virus‐vector specif

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1950.tb00963.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

Roots of young tomato plants became infected when inoculated with tomato bushy stunt, tobacco mosaic, and potatoXviruses. Root infections also occurred when these viruses were added to soil or culture solutions in which plants were growing.The viruses were sometimes localized around their initial entry points in roots; sometimes they invaded the root system but not the shoots, and sometimes they produced full systemic infection of roots and shoots. In some experiments, but not all, systemic infections were more frequent when the upper tap root or superficial roots were inoculated than when fibrous roots were inoculated.In both tomato and potato, virusXspread from diseased to healthy plants sharing the same culture solution, if their roots were in contact, but not otherwise. Infection of the roots of potato plants by inoculation, produced only one plant with virus‐infected haulms, although several had infected tuber

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1950.tb00964.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

The relative importance in North Wales of various factors said to cause blindness in oats was investigated. It is concluded that a direct attack on the developing panicles by frit fly larvae and by adults and larvae of thrips was of little importance in causing the blindness encountered. Most of the blindness appeared to result from adverse physiological conditions probably operative during early growth. Varying varietal susceptibility to blindness was noted, and the effect on the subsequent panicles of an early insect attack on the vegetative parts of the plant is discussed.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1950.tb00965.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

An account is given of observations made between 1944 and 1948 on beet eelworm and related species ofHeterodera.The host ranges of beet‐, potato‐, pea‐, carrot‐ andGaleopsis‐rooteelworms were studied in the field, on sites where previous information had been obtained of the species ofHeteroderapresent. The beet eelworm attacked plants in the Polygonaceae, Chenopodiaceae, Amarantaceae, Aizoaceae, Caryo‐phyllaceae, Cruciferae, Onagraceae and Labiatae. Considerable differences were observed in the intensity of attack upon different hosts. The Cruciferae contains many efficient hosts and is the most important host family in the British flora. TheGaleopsiseelworm, like the beet eelworm, attacked plants in several families, including the Chenopodiaceae, Caryophyllaceae and Labiatae, which also contain hosts of the beet eelworm. The other root eelworms were more specific, the carrot eelworm attacked only cultivated and wild carrots(Daucus carotaL.), the potato eelworm attacked only plants in the generaSolanumandLy copersicum(potato,Solatium dulcamaraL. and tomato), while the pea eelworm attacked only peas(Pisutn), beans and tares(Vicia).The potato eelworm did not attackSolanum nigrumL. orS. sarrachoidesSendt. and there was no evidence that potato eelworm is capable of attacking weeds in natural orders other than the Solanaceae. In pot‐tests, the hop eelworm attacked only hops and nettles and the cabbage eelworm only plants in the family Cruciferae. The rates of development of cysts of the beet, potato, pea and carrot eelworms were studied in the field. In all four species, the rate of development was similar and varied with the soil temperature, being slow in spring, more rapid in summer, falling off during the autumn and becoming negligible during the winter. In the pea eelworm, drought caused delay in the invasion of rootlets by eelworm larvae and reduced the intensity of attack. Assuming adequate moisture, the maximum number of generations for all four species is between two and three per year. In practice, the number of generations is also governed by the vegetative period of the host crop. During the host‐range trials and observations on rates of development, fresh cysts were examined in large numbers. Some differences in shape were observed between the larger cysts of the various species. There were also differences in colour and in the number of eggs extruded into the gelatinous egg sac. Analysis of length and breadth measurements suggested that size ranges and regression coefficients are somewhat more valuable than average lengths and breadths, and length‐breadth ratios, which are usually given. The carrot‐root eelworm(Heterodera carotaeJones) is described, and the status of theGaleopsis‐rooteelworm is discussed. The latter is distinct from beet eelworm and appears to be identical with a form found by Goffart in 1936, for which the nameHeterodera galeopsidisis proposed. The observations here recorded do not support the theory of adaptability of root

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1950.tb00966.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

The wind direction during the primary migration ofAphis fabaeScop, gave a plausible explanation of the infestation pattern round the edge of a bean field; but it is emphasized that other factors are involved whose effects have not been adequately‐assessed in this preliminary surve

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1950.tb00967.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

A method is described for producing some hundreds of apterous and thousands of alate virginoparousAphis fabaeevery day continuously throughout the year. Broad beans are used as the host plants, in a ‘production‐line’ arrangement of eleven ventilated breeding cages, with additional cages for starting subcultures and rearing alatae, all contained in a portion of a small greenhouse with supplementary lighting in winter. When running smoothly, the culture requires about half an hour's work by one man per day.An ‘aphid gun’, being a modified type of aspirator catcher, is described, with which large numbers of aphids could be handled and counted rapidly without damaging them.Amodified technique for host‐transference experiments is described, which permits individual leaves to be compared one with another as host‐units for the aphids. Two types of small metal cages are used, both easily attached to leaves in their natural positions on growing plants. One type confines the aphids to a part of a single leaf and is used mainly for determining relative reproduction rates on different leaves. The other type encloses equal areas of two different leaves between which the aphids can move freely, and is used for determining their behavioural preferences. The principles underlying the use of such cages, the experimental procedures and the interpretation of the results obtained

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1950.tb00968.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY