Identification and biocontrol potential of a strain against two pepper diseases

Abstract:

[Background] Pepper southern blight caused by Sclerotium rolfsii and pepper blight caused by Phytophthora capsici have seriously affected the yield and quality of peppers (Capsicum annuum). [Objective] To obtain efficient antagonistic bacteria for the biocontrol of two pepper diseases and provide a theoretical basis for the development of biocontrol agents. [Methods] From the pre-preserved microbial resource library, the strain SEC-197 with strong inhibitory effects on both pathogens was screened out. It was identified by morphological, physiological, biochemical, and molecular analyses. The production of extracellular enzymes and plant growth-promoting effect of the strain were assessed. PCR amplification was employed to mine the genes associated with the inhibitory and promoting effects. Furthermore, the biocontrol and plant growth-promoting effects of the strain were evaluated by pot experiments. [Results] The strain SEC-197 showed inhibitory rates of 76.59%±0.59% and 74.85%±0.35% against S. rolfsii and P. capsici, respectively. Strain SEC-197 was identified as Bacillus velezensis, which can form biofilms and had the ability to secrete proteases and cellulases, dissolve organic and inorganic phosphorus, produce siderophores, and fix nitrogen. The strain carried biocontrol and growth promotion-related genes such as srfAB, fenB, and ynsE. The pot experiment results showed that the strain had the control effects of 72.08% and 70.42% against pepper southern blight and pepper blight, respectively. Moreover, the strain’s fermentation broth significantly increased growth indicators such as stem width, fresh weight, and dry weight of pepper plants. [Conclusion] The strain SEC-197 has significant antagonistic activity against both pepper southern blight and pepper blight and an obvious plant growth-promoting effect. The research finding provide a theoretical basis and experimental foundation for the practical application of pepper production.