Study of new biocontrol bacterial agent Bacillus velezensis S41L against Rosellinia necatrix

Abstract

White root rot in woody plants is mainly caused by the necrotrophic phytopathogenic fungus Rosellinia necatrix. In this study, we isolate antagonistic bacteria from rhizospheric soil from asymptomatic pear trees infested with white root rot. Furthermore, we isolated 40 bacterial strains and screened them for antagonistic activity against R. necatrix. Then, we selected antagonists that retarded pathogen growth for >30 days. Finally, the strain that exhibited >80 % inhibitory activity against all R. necatrix strains (Korean Agricultural Culture Collection 40446, 40445, 40447, and 40168), demonstrating its effectiveness in controlling this pathogen prevalent in Korean pear and apple orchards, was selected for further experiments. Strain S41L (OP349111) showed the most potent growth-inhibitory activity against the tested phytopathogens. Microbiological and 16S rRNA gene sequencing analyses revealed that the bacterial isolate belonged to the Bacillus genus and had 100 % nucleotide sequence similarity with Bacillus velezensis in GenBank. This strain also harbored antibiotic biosynthesis genes and possessed plant growth-promoting traits such as phosphate solubilization, indole-3-acetic acid, and siderophore production.