Antifungal activity and application of Bacillus tequilensis A13 in biocontrol of Rehmannia glutinosa root-rot disease

Abstract Background The bacterial genus Bacillus , an important group of bacteria which can suppress phytopathogens, has been widely used in agriculture. However, different species of Bacillus often displayed significant differences in probiotic efficiency and mechanism, suggesting that it is very necessary to investigate the biocontrol potential of new Bacillus isolates, especially from under-evaluated Bacillus spp. Rehmannia glutinosa ( R. glutinosa ), an important traditional Chinese medicinal herb, is affected by a serious root-rot disease caused by the fungus Fusarium solani ( F. solani ) . Biocontrol agents against this root-rot disease in R. glutinosa have yet to be developed. This study explored, for the first time, the activity and biocontrol mechanism of a new Bacillus isolate, Bacillus tequilensis A13, in antagonizing F. solani . Results B. tequilensis A13 displayed a strong inhibitory activity (73.49% ± 1.33%) against F. solani growth in vitro and was able to survive and multiply in the sterilized soil. The results from liquid chromatography electrospray ionization tandem mass spectrometry (LC–MS/MS) and Gene Ontology (GO) analyses indicated that B. tequilensis A13 cell-free supernatant contained six antifungal compounds, eight antifungal compound synthases, and several functional proteins involved in the processes of plant stress resistance, etc. Finally, the joint application of complex fertilizer together with B. tequilensis A13 significantly reduced the incidence of R. glutinosa root rot in the field. Conclusion B. tequilensis A13 strongly inhibited F. solani growth by producing antifungal compounds and proteins associated with plant stress resistance/tolerance, and proved to be a promising candidate biocontrol agent against R. glutinosa root-rot disease. Graphical Abstract