Abstract: In this study, field experiment was conducted to explored the effects ofBeauveria bassianaFE14 andPichiasp. J1 as compound agents (JZ) on tobacco growth, soil-borne diseases and rhizospheric soil microbial community. The results showed that compared with the control group (CK, without microbial agent) at mature stage, the JZ group exhibited significant improvements in agronomic traits, with the maximum leaf area increasing by 42.64%. Additionally, the incidence of tobacco bacterial wilt and black shank in the JZ group was significantly reduced, with relative control effects of 67.86% and 66.67%, respectively. Results of 16S rRNA and ITS sequencing showed that the microbial agent JZ did not cause significantly changes in the diversity of rhizospheric soil microbial community, but it significantly altered the composition and structure. After applying the microial agent JZ, the relative abundance ofRalstonia(the pathogen of tobacco bacterial wilt) in the rhizospheric soil was significantly reduced, while the relative abundances of certain antagonistic microbes, such asPenicilliumandSphingomonas, were significantly increased. Furthermore, the microbial agent JZ also significantly increased the contents of soil organic matter and total nitrogen. In conclusion, the mixed application ofB. bassianaandPichiasp. J1 could significantly improve the rhizospheric soil microecology, promote tobacco growth, and provide effective control of tobacco soil-borne diseases.

Key words: bacterial wilt, black shank, microbial compound fertilizer, fungal community, bacterial community