Effects of biochar combined with Trichoderma brevicompactum 6311 on pepper phytophthora blight and pepper growth

Pepper phytophthora blight is a major soil-borne plant disease that negatively affects chili production. Biochar and biocontrol microorganisms have each been shown to independently control plant diseases. However, their collective effects on reducing the incidence of pepper blight and regulating changes in the rhizosphere microbial community have not been investigated. In this study, 4% (w/w) biochar, Phytophthora capsici strain, and our previously screened biocontrol strain Trichoderma brevicompactum 6311 were used in pot experiments and evaluated. Biochar combined with T. brevicompactum 6311 (B + T treatment) exerted the highest control effect on pepper phytophthora blight with an incidence of 55.56%, which was noticeably greater than that in the other groups. In addition to disease suppression, the B + T treatment promoted pepper plant growth by increasing key growth and photosynthetic parameters, enhancing leaf and soil enzyme activities, and improving soil fertility. Analysis of the above indicators and the microbial community in the rhizosphere of chili peppers revealed that the combined effects of disease inhibition and growth promotion under B + T treatment may be as follows: (1) improved plant physiology and leaf defense responses, (2) increased microbial diversity and richness in rhizosphere soil and relative abundance of microorganisms promoting pepper health and decreased relative abundance of potential pathogens such as Fusarium in pepper, and (3) increased soil organic matter and fertility. Therefore, the combined use of biochar and T. brevicompactum 6311 reduces the occurrence of pepper phytophthora blight by enhancing the physicochemical properties, enzyme activity, and synergistic effect of the rhizosphere microbial community.