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Acquired Tolerance to Blasticidin-S in Pyricularia oryzae. Byung Kook Hwang, Former Graduate Student, Department of Agricultural Biology, Seoul National University, Suweon, Korea, Senior author’s present address: Department of Plant Pathology, Institute of Agricultural Sciences, Office of Rural Development, Suweon, Korea; Hoo Sup Chung, Professor, Department of Agricultural Biology, Seoul National University, Suweon, Korea. Phytopathology 67:421-424. Accepted for publication 28 September 1976. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-421.

Thirteen naturally-occurring isolates of Pyricularia oryzae varied in tolerance to Blasticidin-S [1-(1’-cytosinyl)-4-[L-3’-amino-5-(1”-N-methylguanidino) valeryl amino]-1, 2, 3, 4,-tetradeoxy-β-D-erythro-hex-enuronic acid benzylamino-benzene sulfonate]. Isolates tolerant to 500, 700, 900, and 1,300 μg/ml of Blasticidin-S were obtained using ultraviolet (UV) irradiation and a high concentration of Blasticidin-S. Tolerance to Blasticidin-S was unstable in all isolates except Bu7, which was obtained from UV-irradiated conidia; that isolate retained a high level of tolerance even after 20 transfers on fungicide-free media. Successive monoconidial cultures of Bu7 were genetically homogeneous for tolerance. The tolerant isolate Bu7 sporulated more profusely and showed a higher percentage of germination of conidia on media with or without fungicide than did the parental isolate. The Blasticidin-S-tolerant isolate also was tolerant to the antibiotic, Kasugamin, but not to the organophosphorus fungicides, Hinosan and Kitazin. Isolate Bu7 was more virulent on seedlings of some rice cultivars than was the parental isolate.

Additional keywords: rice blast, antibiotics.