摘要:

AbstractExperimental researches in Oltrepò Pavese (Padana Valley), on wheat rust epidemiological aspects related to the climatic conditionsOur experimental researches began in 1976 in Oltrepò Pavese, one of the most important seedwheat growing environment in the Padana Valley.Wheat rust epidemiology, on the cv San Pastore, was studied in relation to the following climatic conditions: temperature and rain. Therefore, after having illustrated the modalities of observation and survey of the three rusts, we studied the infection behaviour on plants in field and hence the infection behaviour on the single leaves. In the end, knowing, by statistical analysis, the relations between infections and climatic parameters, it was possible to define as follows.By comparing the three rusts infections in our environment, we noted that San Pastore wheat has been more affected byPuccinia striiformisWest. with maximum infection points of 26,4 % on the leaves. We noted the greater development of this infection from the fourth to the sixth observation, in correspondence with average values of T° max rising from 23,7° to 26,4°C; in the same period, precipitations varied with a daily average from 3,0 to 1,7 mm.BothP. striiformisandP. reconditaRob. ex Desm. appeared when the average of the T° max was 20,6°C, and in lack of rain.P. reconditahad a development rising from the fourth to the sixth observation showing, with regard toP. striiformis, lower demands of humidity and relatively greater demands of temperature; in fact, it reached a maximum point of infection of 26,4 % on the leaves, assuming a more gradual development thanP. striiformis.P. graminisPers. appeared much later, as it needs higher T° max, followed by rains. Indeed, it appeared with average T° max of 23, 8 °C and with average daily rains of 0,4 mm, rising above all at the sixth observation with 26,4° C and 1,7 mm, respectively.So, we can affirm that the actual experimental investigations point out and confirm what has been already met by other Authors, that is: a) among the three rusts considered,P. striiformisandP. reconditashow to begin their development at the same time, in climatic conditions characterized by T° max relatively mild and high environmental humidity; b)P. striiformisshows, afterwards, the highest infections percentages; c)P. graminisappeared much later reaching modest infection

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00856.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractPerithecia ofErysiphe cichoracearum(powdery mildew) were found on several, but not all, accessions ofLactuca serriola, L. saligna, L. aculeataandL. serriola × L. sativahybrid. Their occurrence varied betweenLactucaspecies and different accessions of the same species. Perithecia were globular, had a mean diameter of 125.5 μm and contained an average 13–14 asci. Asci had mean dimensions of 55.0 × 26.1 μm and each contained two ascospores which measured an average 17.4 × 10.6 μm. There were however significant differences in the dimensions of spores and other structures obtained from differentLactucaacc

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00857.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractAphid transmission studies of two soybean mosaic virus isolates have shown that both isolates are transmitted byMyzus persicae. Only one of the isolates is transmitted byRhopalosiphum maidis. TheR. madisnon‐transmissible isolate could be transmitted from plants co‐infected with theR. maidistransmissible isolate; aphid acquisition factor did not seem to mediate this transmission. The two isolates could be differentiated by enzyme‐linked immunosorbent assay experiments, but peptide mapping experiments revealed few differences between the iso

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00858.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractInvestigations on the influence of aluminium ethyl phosphite on the plant phenolic metabolism in the pathogen‐host‐interactionsPhytophthora fragariae ‐strawberry andBremia lactucae ‐lettuceAluminium ethyl phosphite exhibited pronounced preventive and very good curative activities. In strawberries, 4000 ppm of the compound affected an eminent protection againstPhytophthora fragariaeafter root and leaf applications; the earlier the fungicide treatment was carried out, the more distinct was the control effect. Similar relations were established in the pathogen‐host‐interactionBremia lactucae, in which 5000 ppm of the fungicide proved to be highly active following pre‐ and postinfectional applications.In both parasite‐host‐interactions, an enrichment of phenolics in consequence of ade‐novo‐synthesis in diseased plant tissue was observed only very late and exclusively, when fungicide and parasite had come together; inoculation on one hand or fungicide treatment on the other resulted in no remarkable effect.With great certainty, however, the augmentation of phenolics was not the cause, but rather the consequence of fungicidal efficiency which resulted in killing of the fungus and partial destruction of host tissue after direct influence of aluminium ethyl phosphite on the parasite itself. A clear proof for a main and causal evidence of aluminium ethyl phosphite‐induced phenolics for protection of strawberries againstPhytophthora fragariaeand of lettuce againstBremia lactuca

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00859.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractMechanical inoculation of seedlings of 26 tomato cultivars with an attenuated strain of tomato aspermy virus (TAV‐M, ATCC # PV361) resulted in development of only mild symptoms, which had largely disappeared by the time the infected plants had begun to set fruit. Yield trials revealed that plants inoculated with TAV‐M when transplanted at the 6–8 leaf stage displayed no delay in fruit set and had yields only slightly less than uninoculated plants. Cross protection studies carried out in the greenhouse revealed that TAV‐M has the potential to interfere with infection of tomato seedlings by a more severe TAV strain (ATCC # PV127). ‘Pik‐Red’ seedlings inoculated with TAV‐M showed a significant reduction in symptom expression when challenged with the Blencowe strain of TAV 21 days after the initial inoculation with TAV‐M; interference was incomplete

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00860.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractParasitism ofTrichoderma harzianumon Cystosori ofPolymyxa betaeTransmission electron microscope investigations revealed that cystosori ofPolymyxa betaeKeskin are,in vitroconditions, parasitized and completely degraded byTrichoderma harzianumRifai. The hyperparasite showed a high ability in colonizing excised, surface‐sterilized lateral roots of sugar beet and in invading the cystosori present in them. Both the walls of the root cells and of the cysts are enzymatically perforated. However, in cysts penetration, mechanical forces are also involved. After penetration, cysts undergo a rapid degradation and finally they appear to be completely empty or to contain only small amounts of degradated cytoplasm.Cyst walls are also strongly altered and deformed and only two thin osmiophylic residual layers are detectabl

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00861.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractA novel technique has been developed to inoculate the outer epidermal cells of coleoptiles of barley, oats and wheat with S. nodorum. Using this technique, which results in a large number of attempted penetrations, the composition of the material deposited at unsuccessful penetration sites in these cereals have been compared. Although the deposits reacted in a similar manner with some histochemical reagents (ammoniacal silver solution, Coppick‐Fowler reaction, p‐nitrobenzene tetrafluoroborate and Coomassie brilliant blue R250) marked differences occurred between the reactions sites formed by barley and wheat and by oats with other stains (bromophenol blue, nile blue sulphate and Toluidine blue). Chemical treatments used to delignify tissue also revealed differences in these reaction sites. It is concluded that although the reaction sites share some similar components there are significant differences in their chemical struct

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00862.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractPre and Post‐virus‐acquisition starvation ofAphis craccivoraKoch, andAcyrthosiphon pisumHarris resulted in appreciable increase in percentage of transmission of urdbean leaf crinkle virus. Highest transmission occured when aphids were starved for 90 min prior to virus‐acquisition.A. pisumandA. craccivoraon 20 and 80 min of post‐acquisition starvation and 10 and 20 min of virus‐acquisition, respectively inoculated more number of plants. Both the aphids transmitted the virus in probes lasting for one min. However, beyond 5 min of successive transfer on test plants loss in transmissibility was apparent. Viruliferous aphid off the plant retained the virus for a much longer period than on maize plant. The virus appears to be non‐persistently borne in

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00863.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractWhen the urediniospores of three races ofMelampsora medusae, the causal agent of leaf rust of poplars, were exposed to Co60gamma irradiation (range 100–1000 Gy), there were significant differences in the radiosensitivity of the races as assessed,in vitro, by incubation period to flecking and the uredinial survivability percentage. In race 5A the frequency of mutation to virulence onPopulus deltoidescv. T‐173, normally a resistant cultivar, was maximum (1.688 %) at an irradiation dose of 400 Gy. Importance of mutations as source of variability in pathosystems and usefullness of artificially induced mutations in the context of host‐pathogen interactions are disc

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00864.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY