Biocontrol potential of Bacillus subtilis IBFCBF-4 against Fusarium wilt of watermelon

Fusariumwilt of watermelon caused byFusarium oxysporumf. sp.niveum(FON) is a destructive soil-borne disease. The objective of this study was to screen antagonistic bacteria with potential applications for controlling this disease. Strain IBFCBF-4 with obvious antifungal activity against FON and seven other phytopathogens was successfully isolated from a rhizosphere soil. Based on the morphological, physiological, biochemical characteristics and 16S rDNA sequence analysis, IBFCBF-4 was identified asBacillus subtilis. Under greenhouse condition, IBFCBF-4 could significantly reduce the incidence ofFusariumwilt of watermelon by 51.1% compared to the control. The studies on the antagonistic mechanism showed that IBFCBF-4 could cause abnormal swelling and increased branching to the hyphae of FON. Meanwhile, the volatile and non-volatile compounds produced by IBFCBF-4 were able to suppress the mycelial growth of FON. Furthermore, PCR analysis confirmed the presence ofituA,ituB,ituC,ituD,bamD,bmyB,fenB,srfAB,surf,bacA,bacD,bacAB,tasA,mrsAandmrsMgenes involved in the biosynthesis of iturin A, bacillomycin, fengycin, surfactin, bacilysin, tasA and mersacidin, respectively. Taken together,B. subtilisIBFCBF-4 can be used as a potential biocontrol agent againstFusariumwilt of watermelon, but further work is required to improve its efficacy.