Biocontrol bacteria strains Y4 and Y8 alleviate tobacco bacterial wilt disease by altering their rhizosphere soil bacteria community

Abstract Tobacco (Nicotiana tabacum L.) bacterial wilt caused by Ralstonia solanacearum was widespread in recent years, resulting in a great damage in tobacco production. Biological control is an effective measurement for the bacterial wilt, however, related work has not been researched deeply. By screening the biocontrol microorganisms in Wenshan tobacco growing fields in Yunnan province, we discovered a Bacillus amyloliquefaciens strain Y4 and a Pseudomonas sp. strain Y8 that could significantly suppress the growth of R. solanacearum in the culture. The occurrence of wilt disease by field application of Y4 and/or Y8 was 3–4 folds lower than that of the untreatment at different tobacco growth stages. The microbial composition analysis showed that the relative abundance of the Enterobacteriaceae, Sphingomonadaceae, Caulobacteraceae, Sphingobacteriaceae, Flavobacteriacea, Streptomycetaceae, and Burkholderoaceae were significantly increased in the rhizosphere soils of infected tobacco. Moreover, field application of Y4 or Y8 significantly changed the rhizosphere soil microbiota. The relative abundance of the Lactobacillus was increased, however, that of R. solanacearum, Pseudoxanthomonas mexicana, Sphingomonas koreensis, Variovorax paradoxus, and Bradyrhizobium elkanii were decreased. Our results indicate that biocontrol microorganisms reduce plant disease occurrence by changing their microbiota in rhizosphere soil.