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Inter-Isolate Heterokaryosis in Pyricularia oryzae. Javad 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 68:1791-1794. Accepted for publication 5 June 1978. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1791.

Heterokaryons were synthesized between: (i) monoconidial cultures, (ii) monoconidial cultures and field isolates, and (iii) filed isolates of Pyricularia oryzae. Heterokaryotic hyphae appeared as a solid line of white mycelial tufts where contact occurred between colonies of compatible isolates when they were paired on an agar medium containing polished rice plus rose bengal. A mycelial fragment was taken from each of many tufts and allowed to grow. Hyphal tips from the resulting colonies provided cultures that were allowed to sporulate. Fifty or more monoconidial isolates were obtained from each hyphal tip isolate. Both parental types and some nonparental types were recovered in most instances. Thirteen of 20 different combinations involving 12 different field isolates produced heterokaryons. The percentage of heterokaryon formation varied from 1.5 to 17.75. Heterokaryons also were formed between monoconidial progeny of one isolate (race IB -1, Texas) and field isolates. In addition, 7.6% of the crosses among 21 different field isolates produced tufts presumed to be heterokaryons.