Biocontrol Effect Induced by Streptomyces anulatus ZAM4 ‐4 on Phytophthora capsici Causing Pepper Blight in Capsicum annuum

Pepper blight, caused by the soilborne pathogen Phytophthora capsici , poses a formidable threat to pepper ( Capsicum annuum ) production. The prevalent use of chemical fungicides for pepper blight management has been associated with adverse environmental consequences. To address the drawbacks of chemical fungicides in agriculture, the exploration of biological control agents has emerged as a promising alternative. Here, we identified strain ZAM4‐4 as Streptomyces anulatus , which demonstrated potent inhibitory effects against P . capsici by impeding spore germination and zoospore release, while significantly enhancing the activities of superoxide dismutase (SOD), peroxidases (POD) and phenylalanine ammonia‐lyase (PAL). Moreover, the application of ZAM4‐4 fermentation resulted in notably increased height and fresh weight of pepper plants compared to the control group. Interestingly, ZAM4‐4 exhibited compatibility with a variety of conventional fungicides (metalaxyl, dimethomorph and fluopicolide), encouraging us to explore its combined use with fungicides to enhance control effectiveness. Both laboratory and pot experiments provided compelling evidence that the combined application of ZAM4‐4 and dimethomorph achieved a control efficacy comparable to that of high concentrations of dimethomorph alone in combatting pepper blight. Overall, our investigation demonstrated that ZAM4‐4 not only bolstered the resistance of pepper against Phytophthora blight by inhibiting P . capsici reproduction and elevating enzymatic activities, consequently stimulating plant growth, but also displayed improved and sustained control of pepper blight when used in combination with dimethomorph. These findings highlight the promising potential of ZAM4‐4 for future applications in the field of biological control for sustainable pepper blight management.