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Bacteriological and Pathological Characteristics of Wild Types and Induced Mutants of Xanthomonas campestris pv. oryzae. K. Tsuchiya, Research fellow, The International Rice Research Institute (IRRI), Los Baņos, Laguna, Philippines, Present address of senior author: Department of Plant Pathology, Kyushu University, Fukuoka, Japan; T. W. Mew(2), and S. Wakimoto(3). (2)Plant pathologist, The International Rice Research Institute (IRRI), Los Baņos, Laguna, Philippines; (3)Professor of Plant Pathology, Faculty of Agriculture, Kyushu University, Fukuoka, Japan. Phytopathology 72:43-46. Accepted for publication 14 April 1980. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-43.

The relationship between bacteriological and pathological characteristics of wild types and induced mutants of Xanthomonas campestris pv. oryzae was studied. Most strains of the three pathogenic groups found in the Philippines were homogeneous in biochemical and physiological characteristics. Two parent strains, PXO61PT and PXO63-6PT, of different pathogenic groups were treated with Nmethyl-N-nitro-N-nitroso-guanidine (NTG) and 14 induced mutants were obtained, which were classified into three types on the basis of virulence to rice and colony color on peptone-sucrose agar medium. Weakly virulent mutants developed shorter lesions than the parent strains on all rice cultivars that were tested. White colony mutants derived from PXO63-6PT were relatively stable in colony color both in vivo and in vitro, and almost as virulent as the parent strain. Those derived from PXO61PT, however, were unstable in colony color, which spontaneously changed to yellow, and were avirulent. Revertants induced from avirulent mutants of PXO61NT3 by NTG treatment produced different reaction types on rice differentials. Most of the general bacteriological characteristics of all mutants were similar to those of the wild-type strains, however, the phage sensitivity of some mutants had changed.

Additional keywords: bacterial blight, induced mutant, virulence.