Bacillus velezensis YYC promotes tomato growth and induces resistance against bacterial wilt

In the present study, we investigated the effect of Bacillus velezensis YYC on tomato plant growth and its biological control efficacy of bacterial wilt. Results indicated that the number of fibrous tomato roots increased significantly in the growth promotion assays. B. velezensis YYC also significantly reduced the percentage of bacterial wilt in tomato plants in a pot experiment. It may enhance plant basal immunity by increasing the activity of defense-related enzymes, such as PAL, POD, and SOD. RNA-seq analysis indicated that 1,164 tomato genes were upregulated, and 1,877 tomato genes were downregulated in response to inoculation of tomato plants with B. velezensis YYC. It induced the expression of tomato genes related to auxin, gibberellin, jasmonic acid, and salicylic acid, as well as transcription factors involved in plant resistance to pathogens. It also induced the upregulation of genes in the MAPK signaling pathway. This study provides a better understanding on mechanisms associated with growth promotion in tomato and provides a theoretical basis for the use of B. velezensis YYC as a biological fertilizer.