摘要:

AbstractTwenty of twenty‐four chemicals known to induce phytoalexin production in other plants, when used to soak seed, provided effective protection to 3‐week‐old susceptible wheat seedlings against inoculation withHelminthosporium sativum.The number of lesions was very significantly reduced in most of these treatments and there was evidence for inhibition of lesion expansion in a few. Studies with twelve of the more effective chemicals showed that the protective effect persisted at significant levels even in 5‐week‐old plants and that at this stage the inhibitory effect on lesion expansion was more pronounced in most of the treatments. Different treatments led to the development of a moderate to high level of fungitoxicity in young wheat seedlings which gradually declined with age of the plant and disappeared in 5‐week‐old plants. When inoculated at the age of 3 or 5 weeks, plants receiving most of the treatments developed appreciably higher fungitoxicity than the unt

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00865.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractBotrytis fabaespore suspensions containing c. 1, 10, 102, 103, 104, 105, or 106spores/ml were used to inoculate 5, 17 or 30‐day‐old field bean leaves. The percentages of the leaf areas covered by, chocolate spot lesions and the percentages of the leaf areas bearing conidiophores were assessed 1, 6, 12, 14, and 19 days after inoculation. The percentage of the area covered by lesions and the percentage of the area bearing conidiophores (logit‐transformed) increased linearly with increasing spore concentration (log10‐transformed). The proportions of leaf areas covered by lesions and bearing conidiophores were both greater on 17 and 30‐day‐old leaves than on 5‐day‐old leaves. The rate of lesion growth increased with both increasing inoculum dose and increasing leaf age. Generally there was no interaction between the effects of leaf age and the effects of inoculum dose on either lesion growth or sporulation. Two days after inoculation with suspensions of either 104or 106spores/ml, 7‐day‐old leaves grown at 15°C were transferred to –16°C or 2.5°C or kept at 15°C for 4 days. Two days later more spores had been produced on leaves which had been frozen (–16°C) t

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00866.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractHyperparasitism ofUromyces appendiculatusvar.appendiculatusbyVerticillium lecaniiHost Recognition, Penetration and Degradation of SporesCulture filtrates of the hyperparasiteVerticillium lecaniicontain numerous lytic enzymes. When specific substrates were added to the filtrate, degradation of chitin is increased by a factor of 2,25 and degradation of starch is increased by a factor of 1,5. The degradation of uredo‐ and teliospores ofUromyces appendiculatusvar.appendiculatusis documented cytologically. Appressoria‐like structures initiated direct penetration of the spore walls. Additional routes of penetration through the germpores of both sporetypes and the pedicles of the teliospores were observed. Degradation of the spore cytoplasm is described. Sugars on the surface of uredo‐ and teliospores and on hyphae of the hyperparasite were characterized using the gold‐marked lectins Con A and WGA. Their role in the host‐parasite recognition process is

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00867.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractCYMV‐T, CYMV‐C and CYMV‐RS are three strains of CYMV, a nepovirus isolated from chicory in Southern Italy. They are serologically indistinguishable, but display different electrophoretic and analytical ultracentrifugation patterns. In fact the RNAs obtained from CYMV‐T, when analyzed in 2.4% polyacrylamide cylindrical gels, showed the presence of a 170,000 mol. wt. satellite‐like RNA (CYMV‐T Sat RNA) and several other RNAs, whereas CYMV‐RS gave only the genomic RNAs and CYMV‐C, in addition, some ofthe RNAs present in CYMV‐T but not the Sat RNA.When these three strains were assayed onNicotiana glutinosaL., CYMV‐C and CYMV‐RS elicited typical necrotic rings, whereas CYMV‐T infections were symptomless. The conclusions were drawn that CYMV‐T Sat RNA is another low mol. wt. RNA able to display viral disease regulation and that CYMV‐T, CYMV‐C and CYMV‐RS could represent an example of natural oscillation among different st

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00868.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe wilting ofCassia toracaused byFusarium oxysporumwas reduced significantly when inoculated with VAM. Mycorrhizal fungi highly influenced growth stimulation of the seedlings. The population ofF. oxysporumwas reduced in the presence of VAM.

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00869.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractEightHeveaspecies have been shown to be cyanogenic.They all liberated HCN following mechanical tissue injury. Infection ofHevealeaves with conidia of the plant pathogenMicrocyclus uleileads to a large reduction of hydrocyanic acid potential, while only small amounts of HCN are set free from the leaves into the atmosphere. HCN production by infected leaves follows a reproducible pattern with a maximum between 40 and 60 hours after infection.During the entire time of infection free HCN can be detected in the leaves. From leaves of susceptible clones high amounts of HCN are liberated whereas from resistant clones only very little HCN is released. InHeveainfections withM. ulei, cyanogenesis does not lead to defense of the fungal pathogen but impairment of the resistance reaction.

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00870.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractVanderplankdeveloped a model based on the logistic growth system to calculate the apparent infection rate (r) and to estimate plant disease progress. By estimating his r and p∧(infection rate corrected for growth) the results were frequently negative. Kushalappaand Ludwiglater developed another model for adequately correcting the host growth. The present model is a modification of Kushalappaand Ludwig'smodel in which the results are positive in case ofAlternariablight of pigeon pea (Cajanus cajan[L.] Millsp.). The disease intensity increased despite host growth resulting into an epidemic. A factor accounting for leaf fall due to blighting has been taken into consideratio

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00871.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractAn indirect enzyme‐linked immunosorbent assay (ELISA) was used for the detection of zucchini yellow mosaic virus (ZYMV) in cucumber tissues and in its aphid vectorMyzus persicaeSulz. Results showed that the indirect ELISA was more sensitive, than the direct ELISA for ZYMV detection. Indirect ELISA detected ZYMV in leaf disks as well as in leaf extracts, and four 6‐mm‐diameter leaf disks per well were found sufficient for reliable ZYMV detection. In addition, the readings with virus‐free leaf disks were much lower than those of leaf extracts. When using leaf disks, it is possible to shorten the indirect ELISA protocol to one working day but with reduced sensitivity. ZYMV was also detected in its aphid vector by the indirect but not with thedirect ELISA. The best extraction buffer for aphids was found to be 0.2 M phosphate at pH 6.0. However, the difference between the ELISA readings of viruliferous and virus‐free aphids was always very small, and results were not always rep

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00872.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe Sudanese strain of peanut stunt virus was transmitted byAphis craccivora, Aphis solanella, Myzus persicaeandLiaphis erysimi.Of these,A. solanellaandL. erysimiwere reported for the first time as vectors of peanut stunt virus.A. gossypii, A. solaniandRhopalosiphum maidisfailed to transmit the virus. Viruliferous aphids retained the virus for 30 minutes but post‐acquisition starvation beyond 30 minutes resulted in almost complete loss of the virus.A. craccivoratransmitted the virus to four consecutive test plants andA. solanella, L. erysimiandM. persicaetransmitted the virus to three consecutive test plants. It has been suggested that future research programmes should, include resistance to the virus in the major legume crops and that a crop like lucerne (Medicago sativa) which harbours both the virus and its vectors, should not be introduced in the major peanut‐growing areas of the Su

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00873.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractActivity of phenylalanine ammonia‐lyase (E.C. 4.3.1.5) and anthocyanin accumulation were determined in wounded maize (Zea maysL.) mesocotyls. Mesocotyls were wounded with aluminum oxide and were placed in a 15 h light: 9 h dark photoperiod or in the dark. Extractable enzyme activity increased in response to wounding in the photoperiod but not in the dark. Anthocyanin accumulation in mesocotyls placed in the photoperiod decreased in response to wounding. The results are discussed with reference to phenylalanine ammonia‐lyase activity in mesocotyl tissue wounded or inoculated with fungal pathog

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1986.tb00874.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY