摘要:

SUMMARYPlants of Lloyd George and Seedling M raspberry (Rubus idaeus L.) were found in eastern Scotland infected with raspberry ringspot (RRV), a virus to which these varieties were previously considered immune. Most RRV isolates from affected plants caused milder symptoms in herbaceous test plants than did the type isolates of the common Scottish and English strains. In graft‐transmission tests the Lloyd George strain of RRV infected all the raspberry cultivars tested, including those immune to the common Scottish strain. No consistent differences were found between isolates of the two strains inin vitroproperties or serological behaviour. Both strains were transmitted in seed ofStellaria mediaand in soil containingLongidorus elongatus.Possible reasons why the new strain is uncommon in Scotland are discusse

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1968.tb04523.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

SUMMARYIris mosaic virus (IMV) was the only virus isolated from forty‐six bulbous iris plants of twenty‐two cultivars tested; it was common also inIris danfordiaeandI. reticulatabut was not detected in any of fifty‐two rhizomatous iris plants with mosaic symptoms. IMV was transmitted to healthy irises with difficulty by mechanical inoculation but was transmitted efficiently byMyzus persicae.IMV infected eight of forty‐six plant species inoculated mechanically with partially purified virus preparations. Characteristic local lesions without subsequent systemic infection were produced inAmaranthus caudatus, sixChenopodiumspp., andTetragonia expansa; of these,C. quinoaandT. expansawere the best indicator and assay hosts.The virus was moderately stablein vitroand, unlike some similar filamentous viruses, was best purified by differentially centrifuging infective sap clarified with n‐butanol. Partially purified preparations from several hosts were infective, produced one specific light‐scattering zone after centrifuga‐tion in sucrose density‐gradient columns, were antigenic and contained particles of 760 mμ model length. IMV was not serologically related to any of nine similar aphid‐transmitted, f

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1968.tb04524.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

SUMMARYSome factors influencing the transmission of tobacco ringspot virus (TRSV) by seed of soybean,Glycine max(L.) Merr. cv. Lincoln, have been studied.The age of a plant at the time of infection was the most important factor determining the amount of infected seed produced. The inability of TRSV to infect maturing embryos was not due to slowness of virus movement within the host. TRSV was consistently found in the embryo and perisperm tissues of infected seeds but not in the testa.All attempts to control seed‐transmission of TRSV in soybean failed. Storage for 7 months, and heat‐treatment of seed at temperatures near the thermal inactivation point of the virus, failed to inactivate TRSV in infected seeds. Spraying of TRSV‐infected plants with 2‐thiouracil and 8‐azaguanine had no effect on host infection and did not prevent seed‐t

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1968.tb04525.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

SUMMARYTreatment of detached apple leaves in October with urea induced a rapid and prolonged increase in the microbial populations present in the leaves during the winter. These effects were accompanied by a major shift in the population balance from a predominantly Gram‐positive, chromogenic type of microflora to one dominated by Gram‐negative and non‐chromogenic organisms. Fluorescent pseudomonads became particularly numerous in the urea‐treated leaves and many were found to suppress the developmentin vitroofVenturia inaequalis.An organism forming yellow colonies, possessing exceptional activity against the scab fungus, which was also found in urea‐treated leaves, was shown to be a Gram‐negative, peritrichous bacterium.No antagonistic organisms were isolated from untreated control leaves, but many were found–usually chromogenic forms–which appeared to stimulate the scab fungusin vitro.Treatment with urea accelerated the decomposition of the leaves and suppressed the development ofV. inaequalisin the portions of the laminae which remained structurally intact until the following spring.Many of the effects of urea were enhanced by the addition of glucose, streptomycin, or a suspension of aPseudomonassp. isolated from leaves during the winter. Streptomycin alone reduced the total numbers of microorganisms in the leaves but increased the proportion of Gram‐negative organisms: this was associated with diminished ascospore production in the spring.There was no direct evidence that the antagonistic flora stimulated by urea was responsible for the inhibition ofV. inaequalis, and alternative explanati

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1968.tb04526.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

SUMMARYLeaf‐area development in King Edward potato plants infected withVerticillium albo‐atrumandV. dahliaewas examined both in plants with a normal growth pattern and in those where maturity had been artificially delayed. Methods are described for producing uniform, single‐stemmed, initially disease‐free host plants, and for measuring their total and green leaf areas throughout their development.Under both growth conditions the pathogens had no apparent effect upon the initiation of new leaves on the main axis of the plant, but they did influence their subsequent development. During the growing period the pathogens caused stunting, thus preventing the production of the potential maximum leaf area, while at maturity the chlorosis and necrosis of the diseased leaves and their premature fall reduced functional leaf area.In diseased plants in which maturity had been delayed, stunting at the apices was more apparent: internode length, leaf petiolar axis length and leaf area were all smaller than in healthy plants, the greatest reductions being shown in leaf area. Cells in the stunted leaves were fewer and smaller than those in healthy leaves.A direct result of leaf‐area reduction was the development of smaller tubers, with consequent reduction in the fresh weight, and some reduction in tuber number.V. albo‐atruminvariably proved to be more virulently pathogenic thanV. dahliae; the use of an averageVerticilliumindex was shown to be a reliable method for estimating relative virulence since it reflected both leaf area and yield reductions.Delaying host maturity and thus lengthening the period of extension growth conferred some resistance on plants infected withV. dahliae; symptom progression was stopped after its initial expression, and consequently leaf area was increased. This form of resistance was not shown in the plants inoculated withV.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1968.tb04527.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

SUMMARYThe only characteristic symptom produced byVerticillium albo‐atrumandV. dahliaein infected potato plants is unilateral chlorosis and necrosis: this was not shown until the approach of host maturity, and was distinguishable from symptoms of natural senescence only in its slightly earlier expression.Of six species ofVerticilliumtested against potato (King Edward),V. albo‐atrum, V. dahliae, V. nigrescensandV. nubilumwere pathogenic (all produced ‘wilt’ symptoms and relative virulence was in that decreasing order) butV. tricorpusandV. lateritiumdid not induce disease. Isolates ofV. albo‐atrumandV. dahliae, obtained from a number of other host plants, were also pathogenic to potato.Possible reasons are given for the fewness of records of ‘Early dying’ disease (Verticilliumwilt) of potatoes

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1968.tb04528.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

SUMMARYSeveral organic acids, known to occur in many apple varieties, were shown to be present in the juice of the variety Edward VII. When these were supplied separately to the brown rot pathogen,Sclerotinia fructigena, growing in culture, chlorogenic acid and quinic acid were both readily converted to compounds of higher antifungal activity, one of which was 4‐hydroxybenzoic acid. The chlorogenic acid content of concentrated healthy fruit juice was ˜6 mg/g, whereas the corresponding syrup from diseased fruit contained only ˜2 mg/g. The possible significance of this metabolism of chlorogenic acid by the fungus is discus

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1968.tb04529.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

SUMMARYSubstrate for an endogenous oxidation in homogenates of leaves of bean (Phaseolus vulgaris) was traced to two fractions of lipids, each representing less than 2% of the dry weight of leaves. The substrate lipids, tentatively identified as galactosyl diglycerides, yielded linolenic and linoleic acids on acid hydrolysis. Amounts of linolenic acid in total lipids in resistant and susceptible leaves were similar. Amounts of free linolenic acid in resistant leaves increased eightfold to 408.6 μg and in susceptible leaves fourfold to 130.6 μg/g fresh leaf after homogenization and incubation for 16 min at 4 °C. These quantities are sufficient to account during their lipoxidation for the previously reported oxygen uptakes in homogenates. Differences between resistant and susceptible leaves were traced to the activities of lipase systems which liberate linolenic acid from substrate lipi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1968.tb04530.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

SUMMARYWhen Brompton plum, and M. IV and Crab C apple rootstocks grown in pots were inoculated with fruit tree red spider mites (Panonychus ulmi(Koch)), shoot extension was decreased by 7–17%, the dry weight of the new shoot by 21–32%, and the dry weight increments of old stem and roots by 12–30%, and 7–50%, respectively, compared with control plants sprayed with the acaricide tetradifon. Some of these effects were found in a field experiment with Brompton plum, but not with potted M. I apple rootstocks. Infestation of fruiting Lord Lambourne apple trees, also in pots, had little effect on vegetative growth but in one experiment modified fruit setting, and decreased the dry‐matter content, but increased the seed content of harvested fruit. Lighter inoculation caused no damage to Brompton plum. Spraying inoculated Brompton plum rootstocks with tetradifon + TEPP in mid‐June and mid‐July prevented damage, and though August sprays did not prevent damage to the new shoot, the decreases in dry weight increments of old stem and roots were only 9–13% and 11–19%, respectively, compared with 21–25% and 45–50% in infes

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1968.tb04531.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

SUMMARYInfestations of fruit tree red spider mite,Panonychus ulmi(Koch) altered the growth of young plants of plum and apple. At first, damage to the leaves from mite feeding did not affect their photosynthetic rates. The effects on other processes depended on the density of the infestation. Densities of 1–2 mites/cm2of leaf decreased the rate of shoot extension of Brompton plum, but about 0.5 mite/cm2increased it. Less dense infestations apparently caused no damage. The rate of growth of the leaf area of a plant relative to that of the mite population on it determined changes in the mite density, and therefore the effects of infestation. The growth of the root system was decreased before that of the shoots.Later, when some leaves were severely damaged photosynthesis was decreased. The onset and severity of this phase probably depended on the number of mites and days of feeding on individual leaves. The later‐formed leaves were smaller, and sometimes fewer on infested plants. Some plants were infested with too low a density of mites to decrease shoot extension, but grew less in dry weight because of decreased photosynthesis later in the season.The initial effects are ascribed to an imbalance in the growth controlling substances caused by feeding. Radioactivity was detected in the growing regions of plants remote from mature leaves on which14C‐labelled mites were con

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1968.tb04532.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY