• V Arjunarao

      Articles written in Proceedings – Section B

    • Biological control of cotton wilt - I. Soil fungistasis and antibiosis in cotton fields

      V Arjunarao

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      An assay of “wilt-sick” and “wilt-free” soils from cotton growing areas revealed the fungistatic nature of the latter soil to the wilt pathogenFusarium vasinfectum Atk. Screening of the soils for antibiotic producers, revealed that the “wilt-free” soil harbours far more microorganisms antagonistic to the fungus than the other, leading to enhanced “antibiotic index” and “antibiotic value” over the other soil. Among the microorganisms isolated from these soils, actinomycetes were the most potent antagonists.

    • On the pathogenicity ofFusarium vasinfectum Atk - Self-inhibitory principle of spores as a limiting factor in Cotton wilt

      V Arjunarao

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      A method was standardized for conducting pathogenicity ofFusarium vasinfectum Atk., on cotton, using spore suspension instead of conventional soil-oat inoculum. Spore load higher than an optimum seemed to decrease percentage wilt. The spores in high concentrations failed to germinate in glass-distilled water, soil extract and in soil. This apears to be due to some water-soluble self-inhibitory principle released by the spores. This principle might be responsible for the observed decrease in percentage wilt at the higher spore inoculum levels.

    • Biological control of cotton wilt - II.In vitro effects of antagonists on the pathogenFusarium vasinfectum Atk

      V Arjunarao

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      Using the antagonistic actinomycetes isolated from theFusarium “wilt-sick” and “wilt-free” cotton field soils it was possible to confirm production of antibiotic substance(s) by them inin vitro studies. They inhibited spore germination and radial growth of the cotton wilt pathogenFusarium vasinfectum Atk. In addition, various adverse morphological changes were brought about by them on the fungal mycelium. Most of the actinomycetes were seen to lyse both live and heat-killed bud-cells of the pathogen. Similar effect was also observed in soilin situ.

    • Biological control of cotton wilt - III.In vivo effect of antagonists on the pathogenFusarium vasinfectum atk

      V Arjunarao

      More Details Abstract Fulltext PDF

      By adding optimum dose of propagule suspension of antagonistic actinomycetes to pathogen amended sterilized soil, control of wilt in cotton could be effected. Gradual elimination of the pathogen both in rhizosphere of the host and soil was noticed in the presence of antagonists. Incorporation of antagonists directly into the soil controled the disease to a greater extent than “seed treatment” with propagules of antagonists. Efficient control of the disease was observed only with a few of the antagonists when seeds were soaked in their metabolites and sown. Significantly these were fromFusarium “wilt-free” soils.

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