Pathogenic Variability of Monoconidial Isolates of Pyricularia oryzae in Korea and in the Philippines. J. M. Bonman, Associate Plant Pathologist, International Rice Research Institute, P.O. Box 933, Manila, Philippines. T. I. Vergel De Dios, J. M. Bandong, and E. J. Lee. Research Assistant, and Assistant Scientist, International Rice Research Institute, P.O. Box 933, Manila, Philippines, and Head, Department of Plant Pathology, Institute of Agricultural Sciences, Suweon, Korea. Plant Dis. 71:127-130. Accepted for publication 1 July 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0127.

The pathogenic variation among monoconidial isolates of Pyricularia oryzae from single lesions and monospore cultures was examined with two differential cultivar sets. Tests in Korea and the Philippines indicated some variants but fewer than reported previously. Data support the hypothesis that P. oryzae is relatively stable pathogenically and that quantitative resistance to rice blast is not due to extreme pathogenic instability in the fungus.