Biocontrol potential of Bacillus velezensis HG-8-2 against postharvest anthracnose on chili pepper caused by Colletotrichum scovillei

Abstract

Anthracnose caused by Colletotrichum scovillei is a significant disease of pepper, including in postharvest stage. Bacillus species represent a potential microbial resource for controlling postharvest plant diseases. Here, a strain HG-8-2 was obtained and identified as Bacillus velezensis through morphological, biochemical, physiological, and molecular analyses. The culture filtrate showed highly antifungal activity against C. scovillei both in vitro and on pepper fruit. Crude lipopeptide extracts, which had excellent stability, could effectively inhibit mycelial growth of C. scovillei with an EC₅₀ value of 28.48 ± 1.45 μg mL⁻¹ and inhibited conidial germination. Pretreatment with the extracts reduced the incidence and lesion size of postharvest anthracnose on pepper fruit. Analysis using propidium iodide staining, malondialdehyde content detection and scanning electron microscope observation suggested that the crude lipopeptide extracts harbored antifungal activity by damaging cell membranes and mycelial structures. The RNA-seq analysis conducted on C. scovillei samples treated with the extracts, as compared to untreated samples, revealed significant alterations in the expression of multiple genes involved in protein biosynthesis. Overall, these results demonstrated that B. velezensis HG-8-2 and its crude lipopeptide extracts exhibit highly antagonistic ability against C. scovillei, thereby offering an effective biological agent for the control of anthracnose in pepper fruit.