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Implication of Vergosin and Hemigossypol in the Resistance of Cotton to Verticillium albo-atrum. A. I. Zaki, Research Associate, University of California, Riverside 92502; N. T. Keen(2), and D. C. Erwin(3). (2)(3)Associate Professor, and Professor, respectively, University of California, Riverside 92502. Phytopathology 62:1402-1406. Accepted for publication 14 June 1972. DOI: 10.1094/Phyto-62-1402.

Antifungal compounds accumulated in the stele of cotton plants inoculated with Verticillium albo-atrum, but none was detected in extracts from noninoculated plants. The major antifungal compounds isolated from inoculated plants were the gossypol-related naphthaldehydes, vergosin and hemigossypol. Experiments with infiltrated stem internode sections did not show a consistent correlation between varietal resistance to Verticillium wilt and the accumulation of phloroglucinol reactive compounds (“gossypol equivalents”), but antifungal activity was related to resistance. A purified phytotoxic protein-lipopolysaccharide from V. albo-atrum elicited production of the gossypol-related compounds, and elicited vergosin accumulation that was related to varietal resistance. Tolerant cotton plants inoculated with a mild isolate of V. albo-atrum accumulated phloroglucinol reactive compounds and antifungal activity more rapidly than plants inoculated with a severe, defoliating isolate. Vergosin and hemigossypol were antifungal to V. albo-atrum and were more active than gossypol.

Additional keywords: phytoalexins, protein-lipopolysaccharide complex, cross protection.