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Race-Specific Partial Resistance to Blast in Temperate Japonica Rice Cultivars. J. M. Bonman, International Rice Research Institute, P.O. Box 933, Manila, Philippines. J. M. Bandong, Y. H. Lee, E. J. Lee, and B. Valent. International Rice Research Institute, P.O. Box 933, Manila, Philippines; Department of Plant Pathology, Agricultural Sciences Institute, Rural Development Administration, Suweon 440-707, Korea; and E.I. Du Pont de Nemours & Co., Inc., Central Research and Development, Wilmington, DE 19898. Plant Dis. 73:496-499. Accepted for publication 12 January 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0496.

Twenty-nine of 53 japonica rice cultivars and breeding lines tested for resistance to blast disease in nursery trials in Korea and the Philippines showed complete resistance at one or both locations. Seventeen of 24 entries that tested qualitatively susceptible at both locations showed slower disease progress in the Philippines. Greenhouse tests using japonica cultivars Daechang, Nagdong, and Palgeum, and a susceptible check indicated that Korean isolates were more aggressive than Philippine isolates on the japonica cultivars; the isolates were equally aggressive on the susceptible check. The results suggest that race-specific partial resistance caused the slow disease progress on japonica rices in the Philippine nursery test.