Antibacterial activity and rice-induced resistance, mediated by Csurfactin A, in controlling rice disease caused by Xanthomonas oryzae pv. oryzae.

Xanthomonas oryzae pv. oryzae (Xoo) is an important pathogen in rice. Csurfactin A, produced by Bacillus velezensis HN-2, displayed antibacterial activity against Xoo and effectively inhibited its infection of rice. The median inhibitory concentration of Csurfactin A was 9.27 μg/mL. Scanning electron and transmission electron microscopy examination showed that Csurfactin A caused significant damage to the cell wall structure of Xoo cells. On the other hand, dramatic increases in the activity of phenylalanine ammonia-lyase (Pal) and HO content were observed in rice leaves inoculated with Xoo from 0 h to 72 h. Quantitative PCR assays indicated that Csurfactin A exposure upregulated the expression of the genes Pr1a, CatA, and Pal. The results showed that Csurfactin A could inhibit the growth of Xoo and effectively induce rice resistance to Xoo by triggering a hypersensitive reaction (HR) via mediation of the activities of antioxidant-related enzymes. Taken together, Csurfactin A has strong antibiotic activity against Xoo and effectively induces rice resistance to Xoo. These results highlight the potential of Csurfactin A as a biocontrol agent against Xoo in rice.