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Genetics of Heterokaryosis in Thanatephorus cucumeris. N. A. Anderson, Professor, Department of Plant Pathology, University of Minnesota, St. Paul 55101; H. M. Stretton(2), J. V. Groth(3), and N. T. Flentje(4). (2)(4)Research Assistant and Professor, respectively, Department of Plant Pathology, University of Adelaide, Waite Agricultural Research Institute, Adelaide, South Australia; (3)Research Assistant, Department of Plant Pathology, University of Minnesota, St. Paul 55101. Phytopathology 62:1057-1065. Accepted for publication 30 March 1972. DOI: 10.1094/Phyto-62-1057.

Heterokaryon formation in Thanatephorus cucumeris (‘Praticola-type’ AG4) is controlled by two closely linked genes which together are referred to as the H factor. Homokaryons carrying H factors different at either or both genes, when paired, produced tufts of heterokaryotic hyphae. Thiamin and nitrate reductase auxotrophs were used with wild-type monokaryons to establish heterokaryosis. Nonparental H factors were detected at rates of 1.6, 1.7, and 2.2% of the progenies of three isolates. Heterokaryons formed between single-basidiospore cultures obtained from various countries. Fifteen different H factors were obtained. A similar H factor was found in isolates from South Australia, California, and Minnesota, and another factor was common to isolates from England, Canada, and Nebraska. The H factor promotes outbreeding in isolates shown to be primary homothallic.

Additional keywords: Rhizoctonia solani, incompatibility.