Interaction of Rhizobium leguminosarum and Fusarium solani f.sp. pisi on pea affecting disease development and phytoalexin production

Abstract

Pathogenicity of Fusarium solani f.sp. pisi (F. R. Jones) Snyd. & Hans was tested on five cultivars of pea (Pisum sativum L.) under identical conditions; the fungus was more virulent on cv. Arkel and less virulent on cv. Sweet Stringless. Bacterization of seeds with Rhizobium leguminosarum biovar vicieae was highly effective in reducing the severity of root rot of pea. In vitro tests with F. solani f.sp. pisi and R. leguminosarum biovar vicieae showed no antagonistic effects on solid medium. However, growth of both microorganisms was retarded in dual culture. Phytoalexins (pisatin and 4-hydroxy-2,3,9-trimethoxypterocarpan) were isolated from both Fusarium- and Rhizobium–Fusarium-infected pea epicotyls; 4-hydroxy-2,3,9-trimethoxypterocarpan was present in a greater amount in the latter than in the former, while pisatin concentration was similar in samples from both treatments.