Identification of low-virulence strains of Xanthomonas campestris pv. oryzae from rice in the United States.

Inoculation of 3-wk-old and 7-wk-old rice plants with bacteria isolated from lesions confirmed pathogenicity and reproduced symptoms observed in the field. Comparison of the causal organism with Asiatic strains of X.c. oryzae by standard biochemical tests, light and electron microscopy, fatty acid analysis, analysis of restriction fragment length polymorphisms, and reaction to monoclonal antibodies revealed numerous similarities but some consistent differences. Virulence of the U.S. strains on TN-1 was much reduced compared with strains from the Philippines. This is the first report of X.c. oryzae in the United States