Biochemical basis of genotypic and bio-agent induced stem rot resistance in groundnut

Abstract

Stem rot (Sclerotium rolfsii Sacc.) resistance in groundnut genotypes was due to activities of defense enzymes such as, catalase, peroxidase and polyphenol oxidase. Bio-agent, Bacillus amyloliquefaciens isolated from groundnut rhizosphere enhances the activities of defense enzymes through salicylic acid induced systemic resistance. In resistant genotypes (NRCGCS-19 and NRCGCS-319) higher activities of defense enzymes were recorded constitutively while in susceptible genotypes it was increased after bio-agent treatment. The activities of pathogenesis related-proteins viz., polygalacturonase and chitinase were registered in plants inoculated with S. rolfsii. Enzymes, catalase, peroxidase, polyphenol oxidase and chitinase showed strong negative correlation with disease severity index. However, the activity of polygalacturonase was directly related to disease severity index and inversely related to activity of chitinase. Hence, to obtain required levels of crop protection against S. rolfsii one has to grow either resistant genotypes or bio-agent treated susceptible genotypes.