The effect of application of Bacillus velezensis BHZ-29 on soil microbial diversity in cotton field in Korla region

Objective To explore the effects of Bacillus velezensis on soil microbial diversity in cotton-growing fields, so as to provide a theoretical basis for the green ecological control of cotton Verticillium wilt.

Methods Soils from cotton fields with different occurrence severities of cotton Verticillium wilt in Korla City, Xinjiang were taken as research materials. The biocontrol agent Bacillus velezensis BHZ-29 was applied, and high-throughput sequencing technology was adopted to investigate the soil microbial community structure of experimental cotton fields. The correlations between the biocontrol agent BHZ-29 and soil microbial diversity as well as population structure were analyzed, so as to reveal its influences on the differences in soil microbial community structure in Verticillium wilt-affected cotton fields of Korla City.

Results Five phyla, 11 classes and 31 genera of fungi, together with 10 phyla, 24 classes and 35 genera of bacteria were detected in soils of Korla City cotton fields applied with biocontrol agent Bacillus velezensis BHZ-29. Among them, Chytridiomycota, Ascomycota, Unclassified_k_Fungi, Mortierellomycota and Basidiomycota were the dominant fungal phyla. The dominant bacterial phyla included Proteobacteria, Actinobacteriota, Chloroflexi and Acidobacteriota. According to the microbial community diversity indices (Shannon, Simpson) and richness indices (Ace, Chao) of cotton-field soils in Korla City, the richness and diversity of fungal communities decreased significantly. For bacterial communities, no obvious change was observed in richness, whereas bacterial diversity increased significantly.

Conclusion The application of Bacillus velezensis BHZ-29 in Verticillium wilt-affected cotton fields of Korla City can improve the richness and diversity of soil bacteria, while significantly reducing the richness and diversity of soil fungal communities. It increases beneficial bacterial flora and lowers the risk of pest and disease outbreaks, laying a theoretical foundation for the green ecological control of cotton Verticillium wilt in Xinjiang.