Effects of metalaxyl on elicitor activity, stimulation of glyceollin production and growth of sensitive and tolerant isolates of Phytophthora megasperma f.sp. glycinea

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Abstract

Mutants of Phytophthora megasperma f.sp. glycinea races 1,4 and 6, tolerant to high concentrations of metalaxyl (50- > 500 μg ml−1), were isolated from colonies irradiated with ultraviolet light. When these metalaxyl-tolerant isolates were used to inoculate hypocotyls of compatible soybeans treated with metalaxyl, a majority caused symptoms typical of compatible interactions with rapidly spreading lesions and low levels of glyceollin. This contrasted with the restricted brown lesions with high glyceollin content that developed following inoculation with the parent (metalaxyl-sensitive) isolates. However, a few of the mutant isolates that tolerated 500 μg metalaxyl ml−1in vitro were sensitive (⩽ 10 μg ml−1) in inoculated plants and caused restricted brown lesions. Comparisons were made of the release of elicitors of glyceollin into culture fluids of a metalaxyl sensitive and a tolerant isolate following addition of metalaxyl to the culture medium. Elicitor activity was increased significantly by metalaxyl treatment in culture fluids of the sensitive isolate but not in those of the tolerant isolate. After fractionation by gel filtration most elicitor activity was detected in fractions corresponding to the second of two carbohydrate peaks. In general, these results are consistent with the possibility that in infected plants, at marginally inhibitory concentrations of metalaxyl, release of elicitors from fungal hyphae may stimulate host-defence responses in otherwise compatible interactions.

References (31)

  • I.R. Crute et al.

    A laboratory method for screening fungicides for systemic activity against Bremia lactucae

    Annals of Applied Biology

    (1977)
  • L.C. Davidse

    Antifungal activity of acylalanine fungicides and related chloracetanilide herbicides

  • L.C. Davidse et al.

    Resistance to acylalanine fungicides in Phytophthora megasperma f.sp. medicaginis and P. megasperma f.sp. glycinea

  • L.C. Davidse et al.

    Occurrence of metalaxyl-resistant strains of Phytophthora infestans in Dutch potato fields

    Netherlands Journal of Plant Pathology

    (1981)
  • R.A. Dixon

    The phytoalexin response: elicitation, signalling and control of host gene expression

    Biological Reviews

    (1986)
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    The work was supported by a grant from Ciba-Geigy Corporation for New Technology and Basic Research.

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