Induced systemic resistance (ISR) in hot pepper against Phytophthora capsici infection triggered by cell wall oligosaccharide elicitors from Trichoderma species

Induced systemic resistance, one of the mechanisms of biological control is elicited either by oligosaccharides or glycoproteins released from cell wall of fungal bioagents like Trichoderma species. Oligosaccharide elicitors from 10 Trichoderma isolates having biocontrol potential were tested for their ability to elicit ISR in hot pepper against Phytophthora capsici infection. Treatment with elicitors from isolates Th10, Th9, Th33 and Th28 reduced P. capsici infection in hot pepper by 70-80% compared to 100% infection in pathogen inoculated control. Assays of peroxiase (PO), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL) and glucanase revealed that elicitor treatment significantly induced higher enzyme activity in elicitor treated plants compared to control. Induction of more number of isoforms of PO and PPO was also observed. Elicitors from Th10 and Th33 induced two fold increase in PPO and PAL and three-fold increase in PO, while Th28 and Th9 increased PPO and glucanase by two folds. Different enzymes (involved in phenyl propanoid metabolism or hydryolytic enzymes) contributed to ISR in different isolates.