Antibacterial activity and rice-induced resistance, mediated by C15surfactin A, in controlling rice disease caused by Xanthomonas oryzae pv. oryzae

Xanthomonas oryzae pv. oryzae (Xoo) is an important pathogen in rice. C15surfactin A, produced by Bacillus velezensis HN-2, displayed antibacterial activity against Xoo and effectively inhibited its infection of rice. The median inhibitory concentration of C15surfactin A was 9.27 μg/mL. Scanning electron and transmission electron microscopy examination showed that C15surfactin 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 H2O2 content were observed in rice leaves inoculated with Xoo from 0 h to 72 h. Quantitative PCR assays indicated that C15surfactin A exposure upregulated the expression of the genes Pr1a, CatA, and Pal. The results showed that C15surfactin 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, C15surfactin A has strong antibiotic activity against Xoo and effectively induces rice resistance to Xoo. These results highlight the potential of C15surfactin A as a biocontrol agent against Xoo in rice.