Extracellular self-DNA primes Trichoderma asperellum T8a to enhance biocontrol and plant growth promotion in Capsicum annuum L.

The use of microorganisms as biological control agents (BCAs) in agriculture has regained prominence in response to escalating concerns over environmental pollution, human health, and the global food security crisis. Trichoderma species promote plant growth, improve nutrient utilization efficiency and enhance plant resistance to mention a few. Trichoderma asperellum, is a highly effective fungal biocontrol agent, recognized for its high adaptability to different environments. Accordingly, the elicitation of BCAs has emerged as an innovative strategy aimed at enhancing their antagonistic activity while conferring competitive advantages across diverse agricultural environments. In this study, self-DNA was used as an elicitor on T. asperellum T8a, due to its high specificity, simple handling, and biodegradability. Our results demonstrate that self-DNA treatment significantly enhanced spore germination in T. asperellum T8a, increasing germination rates by 32-78%. Furthermore, self-DNA treatments markedly increased SOD and CAT antioxidant enzyme activities (>50%) and gibberellic acid (GA3) production (16-19%) in T. asperellum T8a. In vitro antagonism assays demonstrated that elicited T8a exhibited greater inhibitory activity against Phytophthora capsici (8-10%) and Fusarium oxysporum (11-21%) than the non-elicited control. In addition, T. asperellum T8a elicited with 5 μg/ml self-DNA displayed an expanded volatile organic compounds (VOCs) repertoire, with 24 differential compounds detected. Application of elicited T. asperellum T8a to chili pepper (Capsicum annuum L.) plants increased plant height by 14% and stem diameter by 4%, while significantly enhancing the expression of the defence-related genes pr1 and erf 1. Moreover, catalase (CAT) and superoxide dismutase (SOD) activities increased by 38% and 75%, respectively, in chili pepper plants treated with elicited T. asperellum T8a. Transcriptomic analysis in T. asperellum T8a, revealed targeted gene expression changes associated with protein synthesis and metabolic pathways such as secondary metabolite biosynthesis and energy production, supporting the elicitation's role in boosting T. asperellum performance. To our knowledge, this study provides the first evidence of BCA elicitation using self-DNA.