Induction of systemic resistance by mixtures of fungal and endophytic bacterial isolates against Pythium aphanidermatum

Abstract

The efficacy of eight fungal and ten endophytic bacterial isolates were tested for their ability to inhibit the growth of Pythium aphanidermatum, the causal agent of chilli damping-off. In vitro studies revealed that Trichoderma viride (TVA) and endophytic Pseudomonas fluorescens (EBL 20-PF) showed the highest inhibition of mycelial growth (71.5%; 76.7%) of P. aphanidermatum. Both the antagonists were compatible with each other and they were tested alone and together in vivo for the control of P. aphanidermatum. Besides, the induction of defense-related enzymes such as peroxidase (PO), polyphenoloxidase (PPO), phenylalanine ammonia-lyase (PAL), PR-protein like β-1, 3-glucanase and the accumulation of phenolics in chilli seedlings due to the application of bioagents were also studied. Combined application of talc-based formulation of bio-agents and challenge inoculated with P. aphanidermatum recorded maximum induction of defense-related enzymes, PR-proteins and accumulation of phenolics compared with individual application. This study suggest that the increased induction of defense-related enzymes (four to fivefold) and phenolic content (sixfold) due to the combination treatment of bioagents might have involved in the reduction of damping-off incidence and in turn increased the plant growth and yield of chilli.