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Basidiocarp Induction, Nuclear Condition, Variability, and Heterokaryon Incompatibility in Athelia (Sclerotium) rolfsii. Z. K. Punja, Postdoctoral research associate, Department of Plant Pathology, University of California, Davis 95616, Present title and address of senior author: Visiting assistant professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650-5397; R. G. Grogan, professor, Department of Plant Pathology, University of California, Davis 95616. Phytopathology 73:1273-1278. Accepted for publication 13 April 1983. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-1273.

One hundred single-basidiospore (S1) strains were obtained from 10 field isolates of Athelia rolfsii from California that formed basidia on potato-dextrose agar containing 2% activated charcoal (C-PDA). They showed pronounced variability in growth rate, sclerotial production, and frequency of clamp formation, suggesting that the field isolates from which they were derived were either heterokaryotic or diploid. Of these 100 S1 strains, 85 formed the basidial state in culture. An additional 62 field isolates of A. rolfsii from various hosts and geographical areas also varied in growth rate, sclerotial formation, and frequency of clamp formation; of these, 36 were previously induced to fruit on C-PDA. The hyphal tip cells of field isolates and S1 strains were multinucleate, and discharged basidiospores contained two nuclei. Antagonism zones formed in pairings among sibling or non-sibling S1 strains, but isolations made from the zone of interaction of 120 of these pairings yielded six morphologically distinct colonies, two of which were shown to be heterokaryotic by fruiting and progeny analysis. Formation of the antagonism zone in pairings between S1 strains (heterokaryon incompatibility) is not a complete barrier to formation of heterokaryons.

Additional keywords: heterokaryosis, teleomorph.