Abstract
Plant diseases caused by phytopathogenic fungi are one of the leading factors affecting crop loss. In the present study, sixty-one Streptomyces strains were screened for their antifungal activity against relevant wide range fungal pathogens prominent in Vietnam, namely Lasiodiplodia theobromae, Fusarium fujikuroi, and Scopulariopsis gossypii. Endophytic strain RC2 was the most effective strain in the mycelial inhibition of the tested fungi. Based on phenotypic characteristics, 16S rDNA gene analysis, and genomic analysis, strain RC2 belonged to Streptomyces albus. An ethyl acetate extract of S. albus RC2 led to the strong growth inhibition of S. gossypii Co1 and F. fujikuroi L3, but not L. theobromae N13. The crude extract also suppressed the spore germination of S. gossypii Co1 and F. fujikuroi L3 to 92.4 ± 3.2% and 87.4% ± 1.9%, respectively. In addition, the RC2 extract displayed potent and broad-spectrum antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, and the phytopathogenic bacteria Ralstonia solanacearum and Xanthomonas oryzae. The genome of strain RC2 was sequenced and revealed the presence of 15 biosynthetic gene clusters (BGCs) with similarities ≥ 45% to reference BGCs available in the antiSMASH database. The UPLC-HRMS analysis led to the identification of 8 other secondary metabolites, which have not been reported in S. albus. The present study indicated that RC2 could be a potent biocontrol agent against phytopathogenic fungi. Further attention should be paid to antifungal metabolites without functional annotation, development of product prototypes, and greenhouse experiments to demonstrate effective control of the plant diseases.