ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb00993.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

A study has been made of the incidence of dry rot in seed potatoes in relation to commercial handling methods, and it has been shown that infection following grading by mechanical reciprocating riddles fitted with bare wire screens is more serious than that following normal handling at harvest or during transport. Hand picking, hand riddling and the use of rubber‐spool graders or rubber‐coated screens reduced infection by varying amounts. The higher incidence of the disease in ‘transported’ as against ‘home‐saved’ seed is regarded as being due to machine grading of such stocks some months prior to planting.Contamination of stores or boxes has not been found to play any material part in the spread of infection under commercial conditions unless tubers are roughly handled during storage. As contact infection has been found to be rare, it is considered that the practice of ‘picking over’ stocks during the winter to remove diseased tubers is unnecessary and may lead to further infection.In addition to wounds, lesions of both blight and powdery scab, but not common scab, have been found to be a m

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb00994.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

Examination of 144 samples of seed potatoes affected with dry rot, comprising 1218 tubers, showed the presence of parasitic Fusaria in 91% of the lesions. The parasitic Fusaria consisted of 93%Fusarium caeruleum, 6%F. avenaceumand less than 1% each ofF. arthrosporioidesandF. tricinctum. F. tricinctumhas not previously been recorded on potato in this country.A method is described whereby the presence ofF. caeruleumcan readily be detected in tubers affected with dry rot.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb00995.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

Living tubers were inoculated by a standard method with small quantities of the soil to be tested and held under conditions suitable for infection. The number of dry‐rot lesions that developed was regarded as giving a measure of the soil infectivity; this number, expressed as a percentage of the total number of inoculations, was termed the ‘Infectivity Index’ of the soil.In these experiments, 91% of the lesions were caused either byFusarium caeruleumor by a few otherFusariumspecies of which much the most common wasF. avenaceum.In most instances it proved possible to distinguish the lesions caused by these two groups of fungi in tubers of the variety Doon Star by the colour of the rotted tissues as seen on cutting; isolations showed that 85% of the separations made in this way were correct.Data are given indicating the sensitivity and consistency which may be expected from the m

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb00996.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

Scabiosa caucasicahas been found affected by a new species ofAphelenchoides, herein described and namedA. blastophthorus.The symptoms of disease are destruction of the inflorescences and distortion of the leaves with reduction of the laminae. Similar symptoms were produced in scabious by experimental infestation. The nematode can infest teazle (Dipsacus fullonum), but has not been found naturally occurring on any host but scabious.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb00997.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

Three diseases characterized by vein chlorosis of varying grades of severity are shown to be graft transmissible to a wide range of raspberry varieties. The diseases are thought to be caused by related strains of a virus transmissible byDoralis (Aphis) idaeiV. d. G. and rarely, if at all, byAmphorophora rubiKalt. It is proposed to refer to the diseases and viruses respectively as mild, moderate and severe vein chlorosis.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb00998.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

A chlorotic veinbanding disease of raspberries is shown to be due to a virus transmissible by the aphidAmphorophora rubiKalt. after infection feeding periods of 18 hr. or more.This virus causes leaf symptoms, masked in hot weather, on a wide range of European and North American varieties. Symptoms on the latter are analogous to those of the red raspberry mosaic of American authors.The names veinbanding disease and raspberry veinbanding virus are proposed.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb00999.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

A virus causing a wilt ofDatura stramoniumwas identified as a strain of henbane mosaic virus. It causes necrotic local lesions inNicotiana rustica, and local lesions are demonstrable in tobacco by staining with iodine. Some of the factors affecting its transmission byMyzus persicae(Sulz.) were studied quantitatively using these lesions.Infective aphids differed little in their ability to cause infection, and usually produced two or three lesions. The duration of the feeding puncture did not affect the number of infections and had little effect on the percentage of aphids becoming infective. Transmissible virus did not seem to be continually imbibed while aphids fed on infected plants, and there were indications that it was acquired immediately before aphids withdrew their stylets from the leaf. Aphids became infective when allowed to make feeding punctures into epidermis stripped from infected leaves.M. persicaetransmitted during feeding punctures as brief as 5–10 sec; the probability of single feeding punctures resulting in infection reached a maximum with those lasting from 20 to 30 sec, during which the stylets did not penetrate as far as the centre of the epidermal cell and little or no saliva appeared to be ejected.M. persicaedid not transmit the virus when its stylets were artificially wetted with infective sap.Periods of darkness before inoculation with datura wilt virus increased the susceptibility ofNicotiana rusticato infection by rubbing, but not to infection by aphid

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb01000.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

This paper records some observations on the effect of the virus of aspermy disease of tomato on the formation of the mega‐ and micro‐spores of the plant. The obvious interference by the virus in the normal meiotic processes suggests that this is the cause of the non‐formation of seed in infected plants. It is suggested that the interference by virus with nuclear divisions may be more widespread and of greater biological significance than is at present rea

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb01001.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY

摘要:

Experimental grafting between cloves is very difficult with shoots, and so far has proved impossible with roots. Use has therefore been made of naturally occurring grafts in the study of sudden‐death disease. Volunteer seedlings often grow up closely adpressed to old trees. If the old tree dies from sudden‐death disease, the pole† usually survives, but occasionally it dies almost simultaneously with the old tree. The poles discussed invariably had an independent root system, but those which died were found to have their roots grafted to those of the old tree whilst poles which survived, although closely adpressed to the old tree, had no organic connexion with it. These observations cannot be reconciled with any but a pathogenic hypothesis as to the nature of the sudden‐death

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1952.tb01002.x

出版商:Blackwell Publishing Ltd    

年代:1952

数据来源: WILEY