Influence of Pseudomonas fluorescens–Induced Plant Defenses on Efficacy of Nucleopolyhedrovirus of Helicoverpa armigera in Okra and Tomato

Abstract

Baculovirus-based biopesticides like nucleopolyhedrovirus (NPV) offer management opportunities against Helicoverpa armigera (Hübner). The plant growth–promoting rhizobacteria Pseudomonas fluorescens imparts induced systemic resistance due to enhanced phenolase activity, which could regulate disease expression by baculoviruses. The possibility of integrated use of H. armigera nucleopolyhedrovirus and P. fluorescens on okra [Abelmoschus esculentus (L.) Moench], cv. Arka Anamika, and tomato (Solanum lycopersicum L.), cv. PKM 1, against H. armigera was investigated. The Helicoverpa armigera nucleopolyhedrovirus (HearNPV) was applied to fruit from pot-cultured okra and tomato previously treated with P. fluorescens as a seed treatment (ST), foliar application (FA), or in combination and bioassayed against third instar H. armigera. Application of P. fluorescens as ST and FA, alone or in combination with HearNPV, reduced larval and pupal weights of H. armigera that fed on okra and tomato fruits. Lower percentage mortality (31.25% and 36.25%) due to NPV was noticed in okra and tomato plants, respectively, treated with P. fluorescens through ST + FA. Increased levels of phenol, tannin, peroxidase, polyphenol oxidase, and phenylalanine ammonia lyase were recorded in P. fluorescens–treated plants than in untreated checks. Reduced consumption by H. armigera larvae and inactivation of baculoviruses due to defense-related enzyme induction in P. fluorescens–treated plants could be responsible for the reduction in NPV-induced mortality of H. armigera larvae.