摘要:

AbstractThe antigenic proteins of MLO associated with faba bean phyllody (FBP) occurring in the Sudan were studied by using SDS‐PAGE electrophoresis followed either by silver nitrate staining or by transferring to nitrocellulose membrane probed with specific polyclonal antiserum. No remarkable differences between healthy and FBP infected plants were observed when the gel was colored with silver nitrate. In contrast, after probing the transferred membrane with the specific polyclonal FBP antisera, band formation was only detected with FBP infected plants. These results were treated through an image analyser using a BIOLAB logicial. The analysed proteins measure approximately 18,000 and 36,000 daltons with regard to the protein molecular weight niarkers used (Bio‐Rad). Possibility of the existence of a dimer is discussed. The localization of the bands is the same whatever the origins of FBP:Vicia fabaorCrotalaria saltiana. However, the partial purification of the MLO including differential centrifugations followed by precipitation with polyethylene glycol (PEG) and passage through a column of Sepharose 4B were found to be essential for having clear electrophoretic profi

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01275.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractIn an attempt to find mild virus strains that would cross‐protect sgainst vanilla necrosis potyvirus (VNPV),Vanilla fragransplants in Tonga were surveyed for the presence of mild or symptomless potyvirus infections. Potyviruses were detected by indirect ELISA using a commercially available portyvirus group monoclonal anibody. From 28 plants with mild or symptomless infections two portyvirus isolates, designated V1 and V3, included systemic infections inNicotiana benthamianafollowing mechanical inoculation. V1, which causes a mild mottle inN. benthamiana, is serologically related to VNPV, while V3 which causes mild vein banding is serologically unrelated to VNPV. Prior inoculation with V1 protectedN. benthamianaagainst the severe mosaic symptoms of VNPV when challenge inoculated after 14 and 21 days, but not after 7 days. When V3 was used as the protecting strain, cross‐protection was observed in some, but not all plants, when chalenged with VNPV after 14 and 21 d

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01276.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractNaturally‐occurring epiphytic fluorescent pseudomonads were isolated and characterized in terms of their potential to control fire blight infection of hawthorn, caused byErwinia amylovora.Preliminary testing and selection of antagonists using an immature pear fruit assay gave some inconsistency in the amount of pathogen suppression on the pear tissue and also in the prediction of biocontrol effectiveness on the intact plant.Selected antagonists provided significant but variable control of fire blight under protected (polythene tunnel and glasshouse) conditions, with isolates HL83 and HL99 giving control of both blossom‐blight and shoot‐blight. In some cases the degree of control was equal to that of chemical treatments, including agrimycin 17 and experimental bactericides, and was achieved without any numerical advantage of applied control agent over pathogen. The timing of pseudomonad application in relation to pathogen inoculation was found to have a significant effect on the level of control of blossom

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01277.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe temporal progress and spatial distribution of papaya ringspot virus (PRV) and populations of aphid vectors were monitored in two papaya (Carica papaya) plantations in the state of Veracruz, México. The incidence of PRV had a typical sigmoidal curve and the logistic model was more acceptable for describing the disease progress than the Gompertz model. The rate (rLof increase in disease incidence (0.034 and 0.023/unit/day in Plot A and B, respectively) differed (P = 0.05) between the plots; differences in number of aphids trapped could account for the difference. The initial determination of an apparent regular spatial pattern early in the epidemic, obtained with a quadrat size determined by Greig‐Smith's method (n = 8 plants/quadrat) at 50 % disease incidence, was inconsistent with our biological observations in the field. An arbitrarily selected, square quadrat size (n = 9 plants/quadrat), was more consistent with visual observation for describing the spatial pattern in the field. With 9 plants/quadrat a random pattern was found. Aphid populations had a bimodal distribution at both sites with the highest population peak in December–February and a secondary peak in August–September and change in disease incidence was generally related to the aphid population level in the previous month. None of the five potential aphid vectors (Myzus persicae, Aphis gossypii A.nerii, A.citricolaandMacrosiphon euphorbiae) of PRV in Mexico colonized the papaya plants, however, which may explain the absence of clustering of d

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01278.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractDeterminative laboratory tests which distinguishRhodococcus fasdansfrom all other coryneform plant pathogenic bacteria were used to compare strains of this species with representative strains ofClavibacterspp. andCurtobacteriumspp. The strains were also compared by colony hybridization using genomic DNA fromR. fasciansas a probe. Only strains ofR. fasciansauthenticated with the determinative tests gave positive reactions to the probe.The pathogenicity of strains was tested in seedlings ofLathyrus odoratusL. (sweetpea) grown in soil, and asepticaily in agar in tubes. Fasciation was induced in sweetpea by 20 strains ofR. fascismsfromBegoniasp.,Brodiaea laxa,Carica X heilborniinm.pentagona, C.pubescens, Dahliasp.,Fragaria X ananassa, Lathyrus odoratus, andVerbascum nigrum. Strains of R.fasdansfromChrysanthemumsp.,Gladiolussp., andJusticia brandegeanadid not induce fasciation in sweetpea.

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01279.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractTo determine the plant variable for coupling a disease model to a soybean growth model, effects of soybean rust (caused byPhakopsora pachyrhizi) on soybean were quantified at four levels: vegetative parts, yield components, plant yield, and plot yield. Path analysis was conducted to determine the most correlated components to disease in each level. The responses of vegetative parts, such as shoot weight and branches/plant, to disease effects were inconsistent among cultivars. Yield components responded consistently to disease effects among the cultivars, indicated by the high values of correlation coefficients between disease and the components. Path coefficients indicated that reduction of 100‐seed weight was the most important cause of yield loss in this level. No significant within‐plant compensation was detected using path coefficient analysis except for that between pod length to pod width. The most consistent response to disease effect was at population level. Correlation of disease to plant yield was as significant as these to plot yield. Correlations between disease and these plant levels were in the order of plot yield, plant yield, yield components, and vegetative parts. Regression between plot yield and green leaf area duration (GLAD) from flowering to seed full size was highly significant (P<0,001). This study suggests that green leaf area at population level was the best variable for coupling disease model to crop mo

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01280.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractInfection structures ofMicrodochium bolleyion barley roots and coleoptilesMicrodochium bolleyigrows within roots and coleoptiles of barley either leading to a damage of the tissue or to a symptomless infection. The present work investigated whether these different types of infection are correlated with different infection structures of the fungus. Two types of hyphae were formed infectmg either the rhizodermis or the epidermis. The fungus spread within the cortex only, not affecting the endodermal cells or the vascular tissue. The extend to which the roots were damaged depended on the infection density. Differences in the structure of hyphae formed in symptomless or necrotic parts of the roots were not observed. In both, roots and coleoptiles, hyphae were detected in dead cells only.

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01281.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractPeriodic acid‐thiocarbohydrazide‐silver proteinate (PATAg) reaction for poiysaccharide localization was performed on ultrathin sections of Spurr resin‐embedded tissues ofPhysostegia virgininaandCatharanthus roseusknown to be infected by mycoplasma‐like organisms (MLO). Electron microscopy of PATAg‐treated sections revealed heavy silver deposition on hmiting membranes of all MLO. It was not possible to detect differences m silver deposition within the multi stratified membrane structure because of masking by silver‐grain deposition. Silver deposition was not found in the cytoplasmic region of the MLO. The results indicate the presence of glucide determinants only in the limiting membrane of the MLO. The significance of this finding i

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01282.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractFour rice cultivars, susceptible or partially resistant toPyricularia griseawere evaluated for their apparent infection rates (r) and for terminal severity values in seedlings grown in seedbeds. Susceptibility of partially resistant cultivars decreased when seeded in wet seedbed compared to those grown in raised or upland seedbed. The degree of blast reduction due to flooding varied with rice genotype, seeding rate, and environmental conditions. Flooding was effective in managing seedling blast of partially resistant cultivars but not of susceptible cultivar. Use of a lower seed rate in comparison to a higher seed rate also led to reductions in r‐values and terminal disease severities. However, in case of the susceptible cultivar IR50, effect of seed rate was more pronounced, when low amount and short duration of rainfall occurred. Flooding of wet beds with low seed rate further reduced the blast incidence. Results of this study suggest that with appropriate use of water, seed rate, and partial host resistance there are prospects for effective control of leaf blast in the tropic

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01283.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractTrichoderma harzianumrenderedPythium aphanidermatumandP. myriotylumnon‐viable in Petri dish dual culture. ThePythiummycelia from such cultures showed natural autofluorescence in the regions of interactions, indicating their death. Non‐volatile and volatile fungicidal activities were detected inT. harzianumculture. Lytic activity of β‐(l,3)‐glucanase was detected on the cell walls of thePythiumspp. There was a significant decrease in the disease incidence whenT. harzianumwas incorporated into sterile soil, whereas the effect was insignificant in natu

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01284.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY