摘要:

SUMMARYXylem sap was extracted from cut branches of stone‐fruit and pip‐fruit trees at different times of the year, and analysed for nitrogen and carbohydrate content. Growth ofStereum purpureumwas measured in the different sap samplesin vitro.Nitrogen and carbohydrate levels in xylem sap from peach trees were highest in late winter and early spring, and these samples supported most growth ofS. purpureum.At full bloom the levels of nitrogen and carbohydrate in xylem sap from stone‐fruits (peach, nectarine, plum, cherry) were several times greater than in sap from pip‐fruits (apple, pear), and the growth ofS. purpureumin sap from stone‐fruits was approximately ten times that in sap from pip‐fruits.The results suggest that seasonal variations in susceptibility of stone‐fruits to silver‐leaf disease, and the greater susceptibility of stone‐fruits than of pip‐fruits, are due to differential ability of their xylem saps to support gr

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04565.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYInfection of bean pods withColletotrichum lindemuthianumleads to the appearance in diffusates of a range of fluorescent and phenolic compounds and of at least two inhibitory compounds. These compounds were found to be absent or in reduced concentration in control diffusates, although the inhibitors were frequently observed to appear at low concentrations without infection. Although sugars and amino acids were found to be released into diffusates, variation in the concentration of these stimulants was found to have little effect on spore germination. Evidence from solvent partition, spectrophotometry and chromatography suggests that the two inhibitors can be tentatively identified with inhibitors previously described from French bean, and both appear to be phenolic substances. It is suggested that inhibitor production may be regarded as part of a general change in aromatic biosynthesis following infection.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04566.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYPeroxidase activity and isozyme patterns were investigated in two leguminous species infected with viruses which produced either local necrotic or systemic chlorotic symptoms. Highest peroxidase activity was recorded when the hosts reacted to infection with necrotic local lesions. No new virus‐specific isozymes were found as a result of infection, but some isozymes, apparently associated with senescence, appeared earlier in extracts from leaves showing necrosis than in extracts from healthy leaves, or from infected leaves showing only very mild chlorosis. Increase in peroxidase activity was accompanied by alteration in isozyme patter

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04567.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYThe effects of five different virus inocula on three varieties of plum (Prunus domesticaL.) were studied in a field trial of 10 years duration. The viruses causing line pattern, ringspot, prune dwarf and bark split had no effect on the growth of Marjorie's Seedling and Cambridge Gage, and only that causing prune dwarf stunted Oullins Gage trees. However, these viruses diminished the fruit yield of one or more varieties, and prune dwarf virus seriously decreased the yield of all three. Decline disease, probably caused by a strain ofPrunusnecrotic ringspot virus, developed in Marjorie's Seedling but not in the other varieties. The symptoms first appeared after 5 years and then the trees declined progressively with necrotic ‘incompatibility’ between rootstock and sc

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04568.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYViruses obtained from plum trees infected with either decline, line‐pattern or ringspot diseases were characterized and identified. All the viruses were serologically related toPrunusnecrotic ringspot virus (NRSV); those from trees with decline or ringspot were serologically indistinguishable from cherry strains of NRSV but differed in pathogenicity, whereas the virus from trees with line pattern was closely related to apple mosaic virus. When returned from herbaceous hosts toPrunus, line‐pattern and ringspot isolates reproduced symptoms characteristic of the diseased sources. One virus isolate from trees with decline diminished the vigour of young plum trees. Comparison with other investigations shows that at least two unrelated viruses cause plum line‐pattern disease in America and E

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04569.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYParsnip mosaic virus (PMV) occurs commonly in parsnip in Britain and is transmitted after acquisition access periods of 2–5 min by the aphidsCavariella aegopodii, C. theobaldiandMyzus persicae.It was transmitted by manual inoculation of sap, infecting parsnip, chervil, coriander and carrot plants systemically, and causing local lesions without subsequent systemic infection in eightChenopodiumspp.,Spinacia oleracea, Gomphrena globosa, andToreniafournieri.It lost infectivity inChenopodium quinoasap after dilution to 10‐3–10‐4, heating for 10 min at 55–58 °C, or storage at room temperature for 7–10 days. Preparations partially purified byn‐butanol or chloroform clarification, followed by acid precipitation and/or chromatography on columns of 2% agarose beads, contained filamentous particles, many of which were aggregated or fragmented. Preparations made with chloroform and without acid precipitation contained unaggregated particles of 755 nm normal length, with a sedimentation coefficient of 149S.PMV did not react with antisera to any of fourteen other viruses with filamentous particles. The present cryptogram for PMV is */*

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04570.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYBarley varieties were most tolerant to infection with barley yellow dwarf virus (BYDV) when they grew rapidly, whether the rate of growth was determined by manipulation of the environment or by the innate genetic constitution of the host. A specific, incompletely dominant gene conditioning a high level of tolerance to the virus in certain rapidly growing genotypes in which it occurred naturally, failed to do so when transferred to slower growing genotypes. However, reintroduction into genotypes capable of rapid growth led to full restoration of the gene's effectiveness. Virus‐free aphids recovered BYDV less readily from quick‐ than from slow‐growing genotypes, all homozygous for the tolerance

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04571.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYA barley variety of Ethiopian origin, with a single Mendelian gene con‐fering tolerance to barley yellow dwarf virus (BYDV), was equally tolerant to a number of isolates of the virus, whereas a susceptible European barley was more susceptible to isolates transmitted byRhopalosiphum padiL. than to those transmitted byMacrosiphum (Sitobion) avenae(Fab). However, hybrids between these two varieties homozygous for the Ethiopian tolerance gene were more tolerant to ‘mild’ than to ‘severe’ isolates, irrespective of the vector specificity. The European variety was damaged more severely by all isolates when infected early than when infected late in its development, but the hybrids were damaged more severely byM.awraae‐transmitted isolates when infected late.It is suggested that in susceptible plants the concentration, rather than the virulence, of the virus determines disease severity, whereas the reverse is true in plants possessing a gene which reduces virus multiplication. Virus concentration appears to determine the severity ofR. padi‐transmitted isolates, while virulence determines the severity ofM. avenae‐transmitted isolates. The latter would also seem to be adapted towards

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04572.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYTolerance to barley yellow dwarf virus (BYDV) in five Ethiopian barley genotypes was conditioned by major genes which apparently occurred at, or near, the same chromosome locus in each genotype. The genes or alleles differed in effectiveness, one providing a high, three an intermediate and one a low level of tolerance. In plants having a slow rate of growth, the effectiveness of the tolerance genes tended to be masked, but the effectiveness of the gene or allele which provided the highest level of tolerance was masked to a lesser extent than that of genes or alleles providing low or intermediate levels of tolerance.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04573.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

SUMMARYTwo bulk populations of spring barley lines differing in respect of a single dominant gene for cereal cyst nematode(Heterodera avenae)resistance were used in trials over 4 years to assess the effect of the nematode on grain yield. On an infested site the resistant lines consistently and significantly out‐yielded the susceptible lines by an average of 9 % over the 4 years. On non‐infested sites, there was no difference in yield between the resistant and susceptible lines.To measure changes in the cereal cyst nematode population under continuous barley cultivation, the resistant and susceptible lines were each sown at the infested site on the same plots for 4 consecutive years. The cereal cyst nematode population declined under both susceptible and resistant barley, but more rapidly under the latter. Migratory nematodes, mostlyPratylenchus minyus, were latterly prevalent on all plots.There was no detectable change in the pathogenicity of the cereal cyst nematode population after 3 years of growing resistant bar

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1970.tb04574.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY