Using fungal biocontrol agents to establish systemic resistance in capsicum chillies against Colletotrichum truncatum

Abstract

Two biocontrol agents, Trichoderma harzianum and Trichoderma asperellum, were used in a pot culture experiment to generate systemic resistance in capsicum against Colletotrichum truncatum. Increases in the activities of five defense-related enzymes—peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), catalase (CAT), and superoxide dismutase (SOD)—were used to track the induced resistance. Additionally, phenols and β-1,3-glucanase accumulation were observed in capsicum following challenge inoculation with C. truncatum, which causes anthracnose or fruit rot. Eight days after inoculation (DAI) with the infection, defence enzyme activity peaked. Due to the introduction of induced systemic resistance (ISR), native PAGE analysis showed that extra PO and PPO isoforms were expressed in seedlings treated with biocontrol agents. The plant defence system was activated in response to C. capsici infection in capsicum seedlings that had previously been treated with biocontrol agents. Therefore, it is hypothesised that ISR is the only indirect technique among the many direct antagonistic tools that the evaluated biocontrol agents used to provide capsicum resistance against the virus.