Use of novel chitin amended formulation of Trichoderma asperellum and Pseudomonas fluorescens to induce systemic induced resistance in chickpea [Cicer arietinum L.] against biotic stresses

Abstract

Genetic diversity of antagonistic P. fluorescens, compatibility testing with fungicides at various concentrations and inducing higher tolerance in bioagents to fungicides, bioefficacy of tolerant bioagents against biotic stresses in chickpea grown in different soil stress conditions were studied during doctoral research (2017-18 and 2018-19). The nineteen isolates were obtained on King’s B medium (KB) designated as Pseudomonas fluorescens (Pf-1 to Pf-19) from chickpea. All the characteristics were dominant for the taxonomical classification of P. fluorescens. 16s rRNA specific region of the ribosomal operon was amplified for the precise species-level identification of P. fluorescens. ph1D gene was amplified in all nineteen isolates of P. fluorescens and ech42 region in T. asperellum indicated good diversity of biocontrol activity based on antibiotics genes. The infected plants showed typical characteristic symptoms of dry root rot and wet root rot and exhibited discoloration of tap roots, longitudinal cracking of the stems, stunting, wilting, etc. which revealed firm association of M. phaseolina and R. solani. Internal Transcribed Spacer (ITS) region based sequencing of M. phaseolina and R. solani proved accurate species-level identification of both pathogens. P. fluorescens (Pf-5 from kheda) and native T. asperellum showed the highest inhibition against M. phaseolina and R. solani in vitro. The highest compatibility of T. asperellum and P. fluorescens was recorded with metalaxyl followed by thiram, mancozeb and copper oxychloride. Higher ED50 values for radial growth indicated maximum tolerance of T. asperellum and P. fluorescens for metalaxyl followed by thiram. T. asperellum and P. fluorescens grew cent per cent against metalaxyl. The combined application of chitin amended bioformulation of T. asperellum and P. fluorescens gave highest seed germination, shoot and root length as well as vigour index and stood superior as compared to control in promoting growth parameters in chickpea under paper towel method as well as lowest per cent disease incidence in chickpea for the management of diseases caused by M. phaseolina and R. solani during pot studies as compared to control. The combination of chitin amended T. asperellum + P. fluorescens (talc bioformulation) under pathogen stress condition exhibited increased PO and PPO activities in the root tissues of chickpea from 10 to 30 days after sowing and declined thereafter in all the inoculated treatments. Whereas in the case of pathogen inoculated control, it gradually declined from 10th days after sowing itself depecting induced systemic resistance action.