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Intra-Isolate Heterokaryosis in Pyricularia oryzae. J. Fatemi, Associate Professor, Department of Plant Protection, College of Agriculture, Pahlavi University, Shiraz, Iran; R. R. Nelson, Evan Pugh Professor, Department of Plant Pathology, The Pennsylvania State University, University Park, PA 16802. Phytopathology 67:1523-1525. Accepted for publication 6 June 1977. Copyright 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-1523.

Conidial progeny of some isolates of Pyricularia oryzae differing in colony morphology and/or color produced heterokaryons on polished rice agar plus rose bengal when compatible progeny of the same isolate were paired. Heterokaryotic hyphae appeared as a solid line at the point of contact, consisting of mycelial tufts. A mycelial fragment was taken from each of many tufts and hyphal-tip isolates were obtained from the resulting colonies. Fifty or more monoconidial isolates were obtained from each hyphal-tip isolate. Both parental types and some nonparental types were recovered in most instances, demonstrating that the mycelial tufts were heterokaryotic. Three of six isolates tested produced heterokaryons including isolate 301 (Race IG-1, Texas), isolate 310 (Race IC-17, Pakistan), and isolate 314. Heterokaryons were formed at a frequency of 0.75, 3.2, and 15.4% for isolates 301, 310, and 314, respectively. Conidial progeny of isolates 304 (Race IG-1, Louisiana), 307 (Peru), and 351 (Race ID-13, Texas) did not produce heterokaryons.

Additional keywords: rice blast, genetic variation.