Rhizobacterium streptomyces sp. NEAU-383 as a potential biocontrol agent to control tomato bacterial wilt.

The global tomato plants are seriously threatened by soilborne bacterial wilt, which is caused by Ralstonia solanacearum. Biological control agents (BCAs) are considered as a promising strategy. In this study, strain NEAU-383, which exhibited significant inhibitory activity against R. solanacearum, was isolated from the rhizosphere soil of a healthy tomato plant in a serious soilborne diseased field. Based on phylogenetic analysis, ANI values, and digital DNA-DNA relatedness, strain NEAU-383 was included in the genus Streptomyces and may be a potential new species. In pot experiments, both pre-inoculation with the spore suspension and fermentation extracts of strain NEAU-383 could effectively prevent tomato bacterial wilt, and the biological control efficiency was 85.2% and 95.1%, respectively. The fermentation extracts of strain NEAU-383 showed the MIC value against R. solanacearum with 0.8 mg/L, and also exhibited broad-spectrum antifungal activity against 5 phytopathogenic fungi. AntiSMASH analysis of the whole genome sequence of strain NEAU-383 revealed a number of key function gene clusters that contribute to the biosynthesis of active secondary metabolites. Moreover, 10 compounds were detected via gas chromatography-mass spectrometry (GC-MS). The maltol and myristic acid were the dominant active metabolites in the crude extract of strain NEAU-383. Moreover, strain NEAU-383 could produce protease and siderophore at a lower level, which also contributed to its antibacterial activity against R. solanacearum. Hence, Streptomyces sp. NEAU-383 may be a potential biocontrol agent used in the management of tomato bacterial wilt and the exploitation of biofertilizer.