Optimization of Bacillus velezensis S26 sporulation for enhanced biocontrol of gray mold and anthracnose in postharvest strawberries

Abstract

The growing demand for organic and pesticide-free food has prompt the adoption of biological strategies for controlling postharvest diseases. While strawberries are appreciated for their sensory characteristics and nutritional value, the pseudofruit are highly susceptible to fungal infections, leading to potential contamination with chemical residues. Bacillus spp. are endospore-forming bacteria that offer an alternative for managing various plant diseases. The present study aimed to investigate the effectiveness of both Bacillus velezensis S26 endospores and endospore-rich inoculant in controlling anthracnose and gray mold in strawberries. Initially, the sporulation process was fine-tuned, followed by the utilization of vegetative cells and endospores for in vitro assays. Subsequently, in vivo assays were performed using an endospore-rich inoculant on strawberries. The optimized sporulation conditions led to the production of 10.3 log10 spores mL−1 after 16 h of cultivation (sporulation yield of 96%). Both the vegetative cells and endospores of B. velezensis S26 inhibited mycelial growth and conidial germination of Botrytis cinerea and Colletotrichum spp., which are the causal agents of gray mold and anthracnose, respectively. While the cell viability of endospores decreased after storage, fresh and stored inoculants proved effective in controlling anthracnose and gray mold during storage. Consequently, the endospores of B. velezensis S26 demonstrated their viability and antagonistic potential against postharvest diseases in strawberries, thereby contributing to an extended bacterial shelf life.