Biocontrol potential of a newly isolated Streptomyces sp. HSL-9B from mangrove forest on postharvest anthracnose of mango fruit caused by Colletotrichum gloeosporioides

Abstract

Mango is an important tropical fruit in the world. Mango anthracnose is one of the most severe postharvest diseases caused by Colletotrichum gloeosporioides . Biocontrol by actinomycetes is considered as a promising strategy. Here, 67 actinomycetes were isolated from mangrove forest soils. A strain labelled with HSL-9B showed 63.21% of the inhibition ratio against C. gloeosporioides and broad-spectrum antifungal activities against the selected seven postharvest pathogens. The strain was assigned to Streptomyces malaysiensis based on the phenotypic, biochemical and whole-genomic profiles . Strain HSL-9B extracts significantly reduced the disease severity of mango anthracnose in vivo . 8 × EC 50 of extracts completely inhibited the infection of pathogen during the entire storage process. Total soluble sugar contents on harvested mangoes were effectively kept. 4 × EC 50 of extracts obviously inhibited spore germination and mycelial growth of C. gloeosporioides , resulting in mycelial rupture and cell ultrastructure destroying. The biosynthesis gene clusters (BGC) of secondary metabolites involved in antagonism were identified by compared with the whole-genome sequencing of strain HSL-9B. Fifteen compounds in strain HSL-9B extracts were obtained using the gas chromatography-mass spectrometry (GC-MS). 12-methyl-tridecanoic acid was one of dominant compounds identified in extracts. Hence, S. malaysiensis HSL-9B is an important bioresource for exploring novel natural products to manage postharvest disease. • Streptomyces strain with strong antifungal activities was isolated and identified. • Strain HSL-9B inhibited mango decay and maintained its quality during postharvest. • Extracts damaged the cell integrity and inhibited spore germination of pathogen. • Biosynthetic gene clusters were found in the sequencing genome of strain HSL-9B. • Several secondary metabolites were identified in strain HSL-9B extracts.