Bacillus velezensis csuftb-96, an efficient and promising biocontrol agent for managing Diplodia shoot blight caused by Diplodia sapinea

Abstract

Diplodia shoot blight, caused by Diplodia sapinea, is seriously endangering the health of pines. Therefore, its prevention and control are urgent. Plant growth-promoting rhizobacteria (PGPR), as potential and highly effective biopesticides, can control a variety of plant diseases. In this study, a PGPR, Bacillus velezensis strain csuftb-96 was isolated from the rhizosphere soil of pines. The plate confrontation test indicated that csuftb-96 severely inhibited the growth of D. sapinea. The pot experiment demonstrated that csuftb-96 has a good control effect on Diplodia shoot blight. The active metabolites of strain csuftb-96, including organic acids, antibiotics, and polypeptides, along with various hydrolases, exhibit significant antagonistic activity, which can cause the hyphae of D. sapinea to become shrunken and ruptured. The application of csuftb-96 significantly enhanced the induced systemic resistance (ISR) of Pinus massoniana and increased the activity of related defense enzymes. By measuring the biomass of the strains in P. massoniana, it was determined that csuftb-96 could successfully colonize. In addition, csuftb-96 has a variety of functions that significantly promote the growth of pine trees. Transcriptome analysis revealed that strain csuftb-96 can induce the downregulation of DNA replication, cell division, and carbohydrate metabolism processes, as well as the upregulation of programmed cell death, thereby inhibiting the growth of D. sapinea. In conclusion, a biocontrol strain csuftb-96 has been discovered that can both directly kill D. sapinea and inducing P. massoniana ISR, thereby controlling Diplodia shoot blight. This study indicates that B. velezensis csuftb-96 has great potential as a biological agent for controlling Diplodia shoot blight and provides theoretical basis for green control of plant diseases.