摘要:

SUMMARYThe green stems and leaves of potted Cox's Orange Pippin trees were susceptible to infection byVenturia inaequalisfrom June to August. Some isolates of the fungus showed conspicuous ability to attack the wood.In the orchard, many conidia were released from pustules in early March (2—3 wk before bud‐burst) but in the 3 years examined (1967—9) most were liberated in April and May. In 1969 it was shown that a decline in numbers in June was accompanied by a decrease in viability of conidia.Infections near the tips of leading shoots were partially controlled by a single treatment with 5% urea (aqueous solution) in October 1966 or 2% urea or 0·01% phenylmercuric chloride (PMC) in March 1967. The subsequent reduction in inoculum was correlated with a reduction in the numbers of primary infections developing on leaves. Basal infections on leading shoots were not susceptible to treatment in October 1967 or March 1968, but in 1969 similar infections were controlled with PMC applied mid‐April when the pustules had burst and were actively spo

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01381.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYColletotrichum musaewas isolated from banana hands I wk after bunch emergence and in subsequent weeks both from fingers and from crown tissue. Other fungi includingFusarium semitectumandNigrospora sphaericawere also isolated. Four pre‐harvest sprays of benomyl, each at 1000μg/ml, controlled these fungi on unripe fruit, but unsprayed bunches covered with polyethylene showed rather increased infection rates.Latent infections ofC. musaegiving lesions on ripe fruit were also largely controlled by the above sprays, but crown rot appearing at this stage was not reduced. One post‐harvest benomyl dip at 250 μg/ml however effectively controlled crown, wound and latent infections. For this reason and also because of the demonstrated risk of benomyl‐resistant isolates ofC. musaeresulting from pre‐harvest treatment, it is suggested that pre‐harvest spraying is

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01382.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYA yellow strain of cowpea mosaic virus (CPMV) was transmitted in cowpea by two thrips,Sericothrips occipitalisandTaeniothrips sjostedti; two chrysomelid beetles,Ootheca mutabilisandParaluperodes quaternus; a curculionid beetle,Nematocerus acerbus; and two acridid grasshoppers,Catantops spissus spissusandZonocerus variegatus.Summarizing trials with single insects, the efficiency of transmission of CPMV averaged 18—21% forN. acerbusand the two grasshoppers, 55% forP. quaternus, and 71% forO. mutabilis.Twenty‐two and 40% of the plants exposed to large populations ofS. occipitalisandT. sjostedti, respectively, were infected. In three trials with an aphid,Aphis craccivora, 4 of 49 plants were infected with CPMV, but these infections were considered spurious because no infections occurred in any of 63 plants exposed to this insect in four other trials. A coreid bug,Riptortus dentipes, did not transmit CPMV. Mosaic symptoms in infected plants appeared 5—39 days after they were exposed to vectors. Infective virus was recovered from fresh faecal pellets of each grasshopper v

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01383.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYAnalyses of published host‐range data for certain viruses reveal correlations with taxonomic groupings of grasses. Barley yellow dwarf virus (BYDV), cocksfoot mottle and phleum mottle viruses are found to have infected greater proportions of the festucoid grasses than of the non‐festucoids to which they were inoculated. By contrast, all strains of sugarcane mosaic virus (SCMV) and of the closely related maize dwarf mosaic virus (MDMV) infected more non‐festucoids than festucoids. In addition, infected plants from grass groups containing higher concentrations of genera susceptible to BYDV, SCMV and MDMV usually show clear symptoms, whereas infected plants from less susceptible groups are frequently symptomless. Some viruses, such as barley stripe mosaic, brome mosaic, cocksfoot streak and ryegrass mosaic, show no apparent preferences for particular grass groups.Samples of grasses employed in host‐range studies are usually strongly biased towards festucoids. It is suggested that viruses ought to be adequately tested against genera from all the major groups, and a classified list of grass genera suitable for host‐range studies is

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01384.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYA mechanically transmissible virus causing leaf mottling and ringspotting ofPassiflora edulisvar. flavicarpa in the Ivory Coast is described. Its particles are flexuous rods 810–830 nm long and 15 nm wide. It infects mainly species of Passifloraceae and Leguminosae;Passiflora foetidais a good diagnostic host.Aphis gossypiiandAphis spiraecolatransmit the virus after brief acquisition feeds. Seed transmission was not detected. In crude sap ofP. edulis, infectivity was lost after 10 min at 65–70 °C, 12–14 days at 24 °C or dilution to 10‐7. A purification method is described, using Triton‐X‐100 as clarifying agent. The virus is serologically related but not identical to passionfruit woodiness virus from Queensland. The virus seems to belong to the potato virus Y group and has the cryptogram */*:*/(6):E/E:S/Ap. It is designated passionfruit r

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01385.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYA survey of the nematode genera associated with trees in Scotland showed thatTylenchussensu lato,Aphelenchoides, Tylencholaimus, Trichodorus, Helicotylenchus, Rotylenchus, Criconemoidess.l.,Hemicriconemoides, Tylencho‐rhynchus, PratylenchusandParatylenchuss.l. were commonly found in soil samples collected from around the roots of coniferous and deciduous trees. OnlyCriconemoidess.l. appeared to have a significant preference for deciduous woods.The presence of undergrowth in woods and forests was associated with significantly greater numbers of plant‐parasitic nematodes.Measurements of abiotic factors indicated that, in mineral soils, pH affected the incidence of most genera, but soil type, moisture content and altitude had little eff

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01386.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYExcessive water in the substratum inhibited germination of monogerm sugar beet seed but it was not lethal, and other crop seeds tested were not as sensitive as beet. The inhibition was not evident in a pure oxygen atmosphere and was lessened when the fruit cap was removed. Although bacterial populations on fruits absorbed appreciable quantities of oxygen, differences between populations in optimum and excessive water were insufficient to account for the inhibition.Anatomical observations revealed the presence of a pore through the sclerified fruit wall at the point of attachment to the mother plant. Evidence indicated that the pore was the route for oxygen and water uptake to the seed, and theoretical calculations of gas flux suggested that oxygen supply would be insufficient to sustain germination when the pore was filled with water.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01387.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARYHeritabilities for shape index (the ratio of bulb height to diameter), based on parent—offspring regressions, were calculated for north European onion cultivars and inbred lines derived from them. Heritability estimates of 0·46 and 0·47 respectively were obtained for the two groups, S0parent bulbs giving S1progenies, and S1parent bulbs giving S2progenies.Within each offspring progeny, the regression of bulb shape index on logebulb weight was significant. The regressions were used to estimate the mean shape indices of the progenies at the same mean bulb weight as their parents, and a series of ‘corrected’ progeny shape means thus obtained. Recalculation of the heritabilities using these ‘corrected’ progeny means gave increased estimates (0·78 and 0·84).By using this regression approach, the breeder can achieve high heritabilities when selecting for a specific mea

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01388.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01389.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

For most of this century, aphids have been known to infest cereals, but their potential importance does not seem to have been fully appreciated until the early 1950s when they were found to be vectors of barley yellow dwarf virus (Bruehl, 1961). Although this discovery initiated a great deal of research in many countries, especially in North America, very little was done, or thought necessary to be done, in Britain. In 1968, however, some of this complacency was lost when the large numbers of aphids found on the cereals in this country indicated how little was known about them and their effects. Aphids are part of a complex four‐dimensional continuum of time and space, and this paper briefly describes some of the results obtained since 196

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1974.tb01390.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY