Submitted to: Proceedings Phytochemical Society of North America 1998
Publication Type: Proceedings
Publication Acceptance Date: 9/7/1999
Publication Date: N/A
Technical Abstract: In greenhouse and field tests with cotton, strains of Trichoderma virens (Gliocladium virens) have demonstrated good biocontrol activity against the seedling pathogen Rhizoctonia solani. UV mutants of effective strains of T. virens that are deficient for antibiotic production and mycoparasitism retain their biocontrol activity. In searching for other mechanisms of action, we find that cotton seedling roots treated with effective biocontrol strains of T virens contain significantly higher levels of phytoalexins as compared to both control plants and to plants treated with ineffective strains of T. virens. These findings have been confirmed in laboratory tests on six different cotton cultivars. We have shown that the cotton phytoalexins are toxic to R. solani. Of these phytoalexins, desoxyhemigossypol and its methyl ether derivative were more toxic than hemigossypol and its methyl ether derivative. Gossypol and its methyl ether derivatives were least toxic. These results indicate that induction of resistance by T. virens in cotton roots, as shown by an increase in phytoalexins, is a mechanism in the biocontrol of R. solani induced seedling disease.