摘要:

Field experiments were carried out from 1956 to 1958 on the effect of soil applications of aldrin on clubroot disease of summer cabbage. In the first two seasons the compound was applied either as a dust, broadcast and worked into the soil, or as an emulsion watered round the plants. Results in 1956 were inconclusive and the same plots were used again in 1957, the same quantities of aldrin being re‐applied. In this season increasing doses of the compound gave increasing control of the disease. The treatment of individual plants with emulsion was more successful than the application of dusts.In 1957 half of each plot received a heavy dressing of ground limestone. Lime alone gave a control equal to that given by the highest aldrin treatment. Lime and aldrin together gave a further reduction in clubbing.In 1958 increasing doses of emulsion were tested. These gave increasing control of disease but the higher doses caused some phytotoxicity which was reflected in a delay in maturation of the crop.A reduction of clubbing from ‘severe’ to ‘moderate’ caused a marked increase in crop, but further reductions in clubbing did not result in any corresponding increase in cr

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1960.tb03497.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

Sclerotia from 6‐week‐old pure cultures ofSclerotium cepivorumgerminated immediately in soil only after abrasion of their rinds, but after burial in soil for a month or more, unabraded sclerotia became capable of germination.Marked stimulation of germination occurred in the presence of host plants (onion, leek and shallot). Little or no germination occurred in soil alone or in the presence of non‐host plants (barley, cabbage, carrot and white clover). Sclerotial germination was observed in a number of soils of widely differing pH and over a wide range of soil water content. Germination of sclerotia on uninjured onion roots was greatest at the tip region. On artificially injured roots sclerotial germination was enhanced but the effect of position was lost.Sclerotial germination was independent of contact between roots and sclerotia. It was induced by root extracts of allAlliumspp. tested, but of no other plants. Boiling or autoclaving root extracts did not destroy the active principle and it is concluded that under field conditions sclerotia are induced to germinate by a thermostable chemical substance fromAlliumroots.The process of germination of sclerotia is desc

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1960.tb03498.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

The incidence of ergot,Claviceps purpurea(Fr.) Tul., in commercial cereal seed samples submitted to the Official Seed Testing Station from 1918 to 1957 has been examined.Rye samples were more frequently contaminated than wheat or barley and no cereal ergots were recorded in oats.A relatively high proportion of ergot‐contaminated rye samples occurred every 8–10 years. This appeared to be associated with high relative humidity and low maximum temperature during June. Similar trends were found for wheat and barley.No varietal differences in susceptibility to ergot contamination were found for rye or barley, but there was some evidence that spring wheat varieties were more frequently contaminated than winter o

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1960.tb03499.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

Commercial samples of celery seed have been submitted to the Official Seed Testing Station, Cambridge, from 1926 to 1958, for tests to determine the percentage infection bySeptorialeaf spot (Septoria apii‐graveolentisandS. apii). The disease test and a method for estimating the viability ofSeptoriaspores is described. The percentage of samples with less than 1% infection increased from 6.1% in 1926‐31 to 46.2% in 1953‐8 and the percentage of heavily infected samples decreased. But celery samples submitted since 1949 for purity and germination only were more heavily infected (in 1953‐8 only 26.3% had less than 1% infection). In 1957‐8, 78.8% of all celery seed samples tested showed evidence of infection withSeptoriaspp.No effect of variety or season on the incidence of disease was found during the survey.Six out of thirty samples were found to carry viableSeptoriaas estimated by germination of pycnidiospores.The similarity between the percentage germination of healthy seeds and those bearingSeptoriapycnidia confirmed the general belief thatSeptoriaspp. do not affect ge

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1960.tb03500.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

Samples of commercial wheat seed submitted to the Official Seed Testing Station, Cambridge, have been examined from 1918 to 1957 for the presence of bunt balls (Tilletia caries(DC.) Tul.) and earcockles (Anguina tritici(Stein.) Filipjev) and the incidence of these organisms is reported.The highest proportion of contaminated samples was found in 1921 (33% with bunt balls and 9% with earcockles). Since then incidence has decreased rapidly and is now steady at less than 1% with bunt balls and nil or less than 0.1% with earcockles. Low bunt‐contamination was confirmed by finding no bunt spores in 122 samples in 1957.The survey illustrates the effective control and almost complete elimination of a seed‐borne disease and pest in the United Kingdom.No seasonal effect on the incidence of either pathogen was found nor was any varietal susceptibility to bunt detec

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1960.tb03501.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

The inoculation of barley with loose smut (Ustilago nuda) using various techniques has given results which do not reflect the known behaviour of varieties under natural conditions. No consistent results have been obtained, but all the varieties thus inoculated could become infected. No variety therefore possessed true physiological resistance and in the field some must escape infection. The inoculation techniques obviously overcame this escape.A method has been devised which, with the varieties used, has reflected their behaviour in the field. Drops of coloured water or spore suspension are allowed to fall from a height on to ears at anthesis. Grains on the ears of varieties which do not become infected in the field do not become coloured or infected (depending on the drops used), while grains of varieties susceptible in the field do become coloured or infected. This is due to the glumes of the former group of varieties remaining closed, and so preventing access of smut spores under natural conditions.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1960.tb03502.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

Twelve glasshouse trials using twenty‐five isolates of coliform soft‐rot bacteria obtained from various countries showed that all the isolates produced typical black‐leg of potato at temperatures of 76° F. (24.5° C.) or over, while some of them could also produce the disease at temperatures below 66° F. (19° C.).Thus the isolates fall into two main groups of which the high‐temperature group originates mostly from tropical or subtropical countries or from plants grown in heated glasshouses, whereas the low‐temperature group is indigenous in the north temperate regions. The high‐temperature group comprisesPectobacterium carotovorum (Erwinia carotovora), P. carotovorumvar.chrysanthemi (E. chrysanthemi)andP. carotovorumvar.aroideae (E. aroideae).The low‐temperature group consists of one variety,P. carotovorumvar.atrosepticum (E. atroseptica).This temperature relation provides a possible means of discovering the origin of the black‐leg pathogen in crops grown from Scottish seed in certain tropical or subtropical countries.As a result of this investigation it is considered that all soft‐rot coliform bacteria are varieties of a single species,P. caro

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1960.tb03503.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

The biochemical characteristics of twenty‐five isolates of soft‐rot coliform bacteria from different countries are recorded. Because of the variability of the reactions, strains capable of producing potato black‐leg at both low and high temperatures, or at higher temperatures only, cannot be distinguished from one another with certainty by biochemical tests alone. They do, however, give an indication of potential pathogenic reactions. Thus the low‐temperature strains correspond withPecto‐bacterium carotovorumvar.atrosepticumand are distinguished from the high‐temperature isolates by their gas production, rapid fermentation of lactose and maltose, methyl red and Voges‐Proskauer reactions and failure to give a positive indole test.Because of their delayed lactose fermentation the chrysanthemum blight pathogen, the carnation slow wilt organism, the guayule bacterium and the organism causing leaf rot ofPhilodendronare classified as a new variety ofP. carotovorum(Jones) Waldee.The diagnosis of the coliform soft‐rot bacteria should be based on qualitative and quantitative biochemical reactions rather tha

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1960.tb03504.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

A coppicing technique was used to determine the incidence and distribution of latent and unrecognized infection around naturally occurring outbreaks of cacao swollen‐shoot virus disease in Western Nigeria. All the apparently healthy trees within 30 yards of eighty outbreaks of various sizes were coppiced and most of the infected stumps which regenerated showed symptoms within a year.The distribution of the infected stumps around thirty‐five outbreaks studied in detail is expressed by the equation log10I=a+bx. Iis the estimated intensity of infection in the coppiced stumps at distancexfrom the nearest infected tree removed at the time of coppicing. The constantadetermines the height of the peak of the infection gradient and increases with outbreak size, whereas the slope of the gradient, determined by the negative constantb, is similar around all outbreaks.The results are consistent with information on the movement of the mealybugs and spread of cacao swollen‐shoot virus in outbreaks. Moreover, they indicate that outbreaks are controlled most economically by removing all obviously infected trees and adjacent apparently healthy ones. Control does not require the destruction of all the trees around outbreaks up to a distance of 30 yards as done previously, but can be achieved by felling fewer trees, the actual number depending on the size of the out

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1960.tb03505.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

The frequency of success of attempts to transmit a virus disease from one plant to another has long been used to measure the effects of any of the factors which influence transmission. Samples are taken from the population under test (e.g. vectors, diseased plants, etc.), and usually one sample is tested on each test plant; this is binomial sampling. However, in the procedure we name the ‘multiple‐transfer method’ more than one sample may be tested on each test plant. This increases the number of samples tested without increasing the number of test plants used, and errors due to heterogeneity in the population under test are therefore minimized. Results from experiments using the multiple‐transfer method may be evaluated by using the maximum likelihood estimator. The method is particularly reliable when the proportion of infected samples being studied is small, but can lead to considerable over‐estimation when the proportio

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1960.tb03506.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY