RESUMO
Biological agent is an important green pathway to control Verticillium wilt. A field experiment was performed to examine the effects of Bacillus subtilis agent (15, 30 and 45 kg·hm-2), Trichoderma humatum agent (15, 18 and 24 kg·hm-2), 'Yufeng 99' agent (15, 22.5 and 30 kg·hm-2) and Zhongnonglyukang agent (30, 45 and 60 kg·hm-2) on cotton Verticillium wilt and soil microbial community. The results showed that all of the four biological agents could reduce the incidence and index of cotton Verticillium wilt, with control effects of 50.0%-77.4% in the whole growth period of cotton. The control effects of B. subtilis, 'Yufeng 99' and Zhongnonglyukang agent were positively correlated with the application doses, while that of T. humatum agent of 18 kg·hm-2 was significantly higher than 15 and 24 kg·hm-2. The relative abundance of V. dahliae was significantly reduced, which was negatively correlated with the control effect. The quantity and species richness of soil bacteria were significantly increased with the increases of application doses. The quantity and species abundance of actinomycete were significantly increased, while the quantity of actinomycete varied greatly among different application doses. The quantity and species richness of fungi increased with the increased application doses of T. humatum agent, but was decreased with the increased application doses of other three biological agents, respectively. The control effect was positively correlated with the quantity of bacteria and actinomycetes, but was negatively correlated with that of fungi. Meanwhile, the control effect was significantly and positively correlated with the abundance of Actinomycetes, Nitrospirae, Ascomycota, Chytridiomycota, but was significantly and negatively correlated with that of Deuteromycota. The application doses of 'Yufeng 99', zhongnonglyukang, B. subtilis and T. humatum agents were suggested to be 30, 60, 45 and 18 kg·hm-2, respectively.
