Suppression of Fusarium wilt of banana by combining acid soil ameliorant with biofertilizer made from Bacillus velezensis H-6

Fusarium wilt is one of the most serious banana diseases. It is caused by the soil-borne pathogen Fusarium oxysporum f. sp. cubense (Foc). The key accepted reasons for disease break-outs are the increasing number of pathogens in soil and gradual soil acidification according to published reports. Few studies have reported management methods to control these two aspects at the same time. In this study, a novel improved biological control method, combined acid soil ameliorant (ASA) with biofertilizer (BIO), was applied to manage Fusarium wilt under greenhouse conditions. A biocontrol agent, Bacillus velezensis H-6, was isolated and used for producing biofertilizer BIO6 for pot experiments. Combined ASA with BIO6 (treatments OBIO6 and ABIO6) showed greater biocontrol efficacy compared with individual treatments by 63.3% and 66.7%, respectively. They also increased rhizosphere soil pH from 4.50 to 4.89 and 5.52, respectively. Correlation analysis showed that the Foc population and Fusarium wilt disease incidence (DI) were both significantly (P<0.05) negatively correlated with pH in the rhizosphere, contents of NH4-N and organic matter (OM), and populations of bacteria and actinomycetes. Furthermore, pH was significantly positively correlated with content of OM and populations of bacteria and actinomycetes, while it was negatively correlated with content of NO3-N and population of fungi. In conclusion, our novel improved biological control method revealed a greater potential to control Fusarium wilt of banana, and the effect might be a result of improving soil acid-alkali conditions to decrease the density of pathogen and manipulating the soil microbial community.