ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1969.tb02869.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

SUMMARYResistance toBrevicoryne brassicaeL. attacks in a New Zealand variety of forage rape resulted from a combination of host non–preference and antibiosis. Using clonal plant material obtained from cuttings, only half the numbers of immigrant alate cabbage aphids that settled to reproduce on the susceptible rape were to be found on the resistant rape. The reproduction rate of these alates was about 12 % slower on the resistant plants than on the susceptibles and the young took about 13% longer to mature. Antibiosis then shortened the reproductive life of the apterae by one‐third, reduced their fecundity by nearly 50 % and caused 40% mortality in their progeny. The over‐all effect of this was considerable and under conditions specified in the text could result in the population on the resistant plants being about one‐eighth that on the susceptible plants in under 1 month. The resistant plants lost their resistance on flowering and became normally susceptible to cabbage aphid attack. With maturity, however, theB. brassicae‐resistant plants became slightly resistant toMyzus

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1969.tb02870.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

SUMMARYFrom the type strain of tobacco mosaic virus, defective strains were isolated that produced chlorotic or ringspot type symptoms in tobacco and were difficult to transmit without carborundum in the inoculum. Their concentration was less than 0–1 μg/ml of sap instead of the usual 2 mg/ml with the type strain. Phenol extracts of infected leaves were a little more infective than extracts in buffer, whereas phenol extracts of leaves infected with type strain were very much less infective than extracts in buffer. Electron microscopy of infective sap rarely showed any virus particles, but preparations concentrated by ultracentrifugation contained virus particles, many of which were broken or seemed inadequately assembled.Changing the ambient temperature at which infected plants were kept from 20 to 35°C did not increase the amount or improve the appearance of the virus. Some of the strains were inactivated during heating for 10 min between 70 and 80 °C.Undiluted sap lost its infectivity in 3 days at 20 °C, as did the type strain when diluted to 0–1 μg/ml in sap from healthy leaves. This is because substances that inhibit infection were produced by microbes in the sap. The ability of sap from healthy leaves to inhibit infection increased by more than twenty‐five times when left 3 days at 20 °C. Infectivity of appropriate mixtures of type strain and aged sap was restored by diluting them in buffer. Sodium azide at 0·02% in sap prevented formation of the inhibitor. The infectivity of the defective strains increased when inoculated together with the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1969.tb02871.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

SUMMARYEggplant mosaic virus (EMV), obtained fromSolanum melongenaL. from Trinidad, is readily transmitted by inoculation of sap to several solanaceous and a few non‐solanaceous plant species. Purified preparations of EMV contain isometric particles 30 nm in diameter, and with sedimentation co efficients of either 111 or 53S.The particles have thirty‐two major morphological subunits. EMV is closely serologically related to Andean potato latent virus and has a similar host range, but is more virulent. Also, whereas EMV accumulates fastest inNicotiana clevelandiileaves at 20–24 °C, Andean potato latent virus accumulates fastest at 15 °C, and fails to attain a serologically detectable concentration at 24 °C. A few symptomatologically or serologically distinguishable strains of EMV were obtained. EMV has properties typical of viruses of the Andean potato latent subgroup of the turnip yellow mosaic group of viruses, and its present cryptogram is */*:*/*:

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1969.tb02872.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

SUMMARYElectron microscopy of thin sections ofLongidorus elongatus(de Man) fed on plants infected with raspberry ringspot and tomato black ring viruses showed virus‐like particles in the lumen of the buccal capsule and in the space between the stylet and the guiding sheath. In sections ofL. elongatusfed on plants infected with arabis mosaic virus, which it does not normally transmit, a few virus particles were seen in the buccal capsule but none was associated with the stylet guiding sheath. It is suggested that the association of virus particles with the cuticular guiding sheath is an explanation of the specificity of virus transmission evident inL. elongatu

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1969.tb02873.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

SUMMARYSeed treatment with thiram reduced post–emergence damping–off, while fumigating forest nursery soils with methyl bromide or DD improved Douglas‐fir seedling emergence, shoot and root growth, and decreased the incidence of root disease.At an old site, where corky root develops, the benefits from these fumigants were associated with fewer(a) Xiphinema bakeriand(b)isolates ofCylindrocarpon radicicola.At a new site, decrease inFusariumroot rot and increase in shoot growth were related to reduction of populations ofParatylenchusandPratylenchus, respectively. In unfumigated soils,Fusarium oxysporumwas isolated from diseased and healthy

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1969.tb02874.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

SUMMARYA method of soaking seeds in an 0·2% aqueous suspension of thiram for 24 h at 30 °C, which had previously been shown to eradicate infection by several fungi, was tested against a further thirteen seed‐borne pathogens. Eleven of these were completely controlled, one was almost completely controlled and one was not adequately controlled by the treatment.The thiram soak treatment was much more effective than dust treatments with fungicides for the control of many internal fungal pathogens. It was also generally more effective and less damaging than hot‐water treatment.The ways of applying the method commercially have been investigated and it is being adopted for the treatment of celery, brassicas and red

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1969.tb02875.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

SUMMARYSeed dressings with Vitavax—75 % w.p.—eliminatedUstilago nudain spring barley seeds and greatly reduced infection due toU. triticiin winter wheat. Emergence and yield of these crops were not adversely affected. Seed soak treatments including 0·2 % aqueous Vitavax for 6 h at 30 °C (wheat and barley), 0·2% thiram for 24 h at 30 °C (barley) and 0·2% Vitavax for 1 h at 30 °C (barley) also rid the seeds of infection. In other tests with barley 2 h soaks in 0·2 % aqueous suspensions of Vitavax at 30 °C gave equivalent control to 12 h soaks in 0·2% thi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1969.tb02876.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

SUMMARYUnderground stems and roots of the potato varieties King Edward and Majestic became more severely infected byOospora pustulans(skin spot) as the growing season advanced. Tubers became infected at their initiation in June and July but the proportion of infected eyes usually increased during both the growth of the crop and bulk storage. Some buds on tubers in bulk stores died in December, but few were killed until after January, when attacks increased until by March about a quarter of Majestic eyes were usually dead. Boxing (chitting) not only prevented most eyes from dying but also prevented much skin spotting on tubers. At High Mowthorpe, Majestic seed unboxed or boxed in March yielded, respectively, 3 and 1 ton/acre less than seed boxed by January. Early boxing increased the yield of seed–sized tubers but did not affect the infection of progeny tubers. Dipping Majestic seed tubers in organo–mercurial fungicide and then boxing soon after lifting decreased their infection byO. pustulans;it also lessened infection on plants they produced and increased the yield of progeny seed–sized tubers. However, dipping, even in successive years, had little effect on the infection of progeny tubers byO. pustulans.Rhizoctonia solaniandHelminihosporum atrovirensbecame increasingly prevalent on tubers during growth after July and during bulk storage.H. atrovirenswas decreased by early boxing or dipping tubers in fungicide. Verticillate conidiophores often grew on incubated tuber plugs but their prevalence was affected by past storage.The results suggest that some of the benefit for chitting may be from disease control, it was not possible to measure the extent to which benefits from chitting depend on effects on disease or on the physiology of the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1969.tb02877.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

SUMMARYSeeding parsnip plants on four commercial holdings in Essex showed not only the root cankers and leaf spots associated with infection byItersonilia pastinacae, but also extensive lesions on the petioles and necrosis of the inflorescences. These last‐named symptoms were proved to be caused byI. pastinacaewhich could also be found on some of the seeds. Seed infection, though largely superficial, was sometimes more deep‐seated. It could be eliminated by soaking the seed in an aqueous suspension of 0·2% thiram at 30 °C for 24 h.Heavily infected seed gave a low percentage of seedlings bearing cotyledon lesions: it is uncertain whether hypocotyl lesions, which also occurred, were caused directly by the fungus.An outdoor test failed to show that infected seed gave rise ultimately to roots bearingItersoniliacankers: the significance of this and other possible sources of infection is disc

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1969.tb02878.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY