VIEW ARTICLE

Resistance

Interaction of Xanthomonas campestris pv. oryzae and a Resistant Rice Cultivar. T. W. Mew, Plant pathologist, The International Rice Research Institute, Los Baņos, Laguna, Philippines; C. M. Vera Cruz(2), and R. C. Reyes(3). (2)(3)Research assistants, respectively, The International Rice Research Institute, Los Baņos, Laguna, Philippines. Phytopathology 72:786-789. Accepted for publication 22 October 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-786.

A rice cultivar, Cas 209 (IRRI Accession 15793), responded differentially to strains of virulence group (VG) II of Xanthomonas campestris pv. oryzae in the Philippines indicating that VG II contains a mixture of strains that are either virulent (VG IIa) or avirulent (VG IIb) to Cas 209. Strains of VG I, VG IIa, VG IIb, and VG III can be distinguished by their differential virulence on the rice differential cultivars IR8, IR20, Cas 209, IR 1545-339, and DV85. The differential reactions were consistent for two inoculation methods and for inoculations at both early tillering and maximum tillering growth stages of rice. The results confirm the presence of pathogenic races of the rice bacterial blight pathogen in the Philippines.