Plant growth promoting rhizobacteria (PGPR) and entomopathogenic fungus bioformulation enhance the expression of defense enzymes and pathogenesis-related proteins in groundnut plants against leafminer insect and collar rot pathogen

The bioformulation of Pseudomonas fluorescens (Pf1 and TDK1) and Beauveria bassiana (B2) strains was evaluated individually and in combinations with and without chitin for their efficacy against leafminer insect and collar rot disease and the effect of the interaction between Pseudomonas, Beauveria and groundnut leafminer insect and collar rot pathogen in the expression of defense enzymes and pathogenesis-related proteins (PR-proteins) in groundnut. Among the various bioformulations, B2 + TDK1 + Pf1 (amended with or without chitin) formulation significantly reduced the incidence of leafminer and collar rot disease when compared to untreated control. A significant increase in the enzymatic activity of phenylalanine ammonia-lyase, peroxidase, polyphenol oxidase, chitinase, beta-1,3-glucanase, superoxide dismutase, catalase, lipoxygenase, and phenolics in groundnut plants treated with B2 + TDK1 + Pf1 bioformulation (amended with or without chitin) and challenge inoculated with Aproaerema modicella and Sclerotium rolfsii. Native gel electrophoresis also revealed the expression of more isoforms of pathogenesis-related proteins and other defense enzymes viz., polyphenol oxidase and superoxide dismutase in plants treated with B2 + TDK1 + Pf1 mixture challenged with A. modicella and S. rolfsii. The present study reveals that sustained and timely induction and accumulation of these defense enzymes and PR-proteins enhance the resistance in groundnut against leafminer insect and collar rot disease. (C) 2013 Elsevier Ltd. All rights reserved.