DEPRESSED METABOLIC ACTIVITY OF VESICULAR-ARBUSCULAR MYCORRHIZAL FUNGI AFTER FUNGICIDE APPLICATIONS

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Summary

Application to soil of either benomyl or captan significantly decreased the growth of vesicular-arbuscular mycorrhizal (VAM) onion (Allium cepa L. cv. Hyper) plants 4 weeks after treatment but non-VAM plants were not affected. Fungal colonization of the onion roots, as indicated by non-vital staining with chlorozole black E, was depressed 2 weeks after fungicide application. However, decreases in metabolically active VAM fungal tissue, revealed by a succinate dehydrogenase assay, could be detected as soon as 3 d after fungicide treatment. There was little difference between the fungicides in their effect on the VAM fungi used. The usefulness of the succinate dehydrogenase assay in predicting effects of fungicide is discussed.

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