First report about the screening, characterization, and fosmid library construction of Xanthomonas oryzae pv. oryzae strain with resistance to Fubianezuofeng.

Bacterial blight (BB), which is caused by Xanthomonas oryzae pv. oryzae (Xoo), is a common bacterial disease that seriously harms rice production in major rice-growing areas worldwide. Fubianezuofeng (FBEZF), a sulfone bactericide that contains an oxadiazole moiety, exerts good control effect on BB. In this study, FBEZF-resistant strains of Xoo were screened for the first time in the laboratory to evaluate the risk of Xoo developing resistance to FBEZF. Three strains with moderate resistance to FBEZF, were obtained and named as F1, F2, and F3, which have resistance factors (RF) of 14.69, 15.72, and 11.12, respectively. FBEZF lacked positive cross-resistance to bismerthiazol, thiodiazole copper, zhongshengmycin and phenazino-1-carboxylic acid. The growth rates of the resistant strains F1 and F2 were similar to those of the wild-type strain in nutrient broth medium, but differed in nutrient agar medium. The extracellular polysaccharide production and pathogenicity of F1, F2, and F3 were reduced relative to those of the wild-type strain. A fosmid library containing 2304 transformants was constructed based on the genome of F2, and transformants 2193 and 2202 exhibited FBEZF resistance. The results are helpful for further study on the molecular mechanism of resistance to FBEZF in Xoo.