Microbial agents suppress jujube black spot disease and enhance jujube yield by regulating soil physicochemical and microbial properties

The jujube black spot disease, caused by the soil-borne pathogenic fungus Alternaria alternata, poses a serious threat to the jujube industry by reducing both yield and quality. Microbial inoculants have been shown to promote crop growth, enhance crop quality, and increase crop stress resistance. However, the mechanisms through which microbial inoculants improve crop yields by modifying soil properties, suppressing pathogenic fungi, and regulating soil microbial communities require further elucidation. In this study, we investigated the antifungal activity of Bacillus velezensis SDTB038 against jujube black spot disease and its tolerance to saline-alkali conditions, and applied it for field control. Additionally, we compared the effects of conventional chemical fertilizers (C-1), commercial microbial inoculants (O-1), and B. velezensis inoculants (B-1) on soil properties, microbial communities, as well as jujube yield and quality. The results showed that strain SDTB038 exhibited significant inhibitory effects on A. alternata and had tolerance to saline-alkali conditions. After applying B-1, multiple soil parameters were significantly improved, including increased levels of soil organic matter, total nitrogen, and available potassium, as well as enhanced activities of soil urease, alkaline phosphatase, catalase, and sucrase enzymes. Furthermore, the application of B-1 resulted in a more complex interaction network among soil microorganisms and promoted the enrichment of beneficial microorganisms such as Bacillus spp. and Sphingomonas spp., while significantly reducing the levels of Alternaria. This led to increased jujube yield and overall quality. This study provides a theoretical basis for the biological control of jujube diseases, quality improvement, and the development of microbial fertilizers.