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Tilletia aegopogonis, a Homo-Heterothallic Bunt Fungus. Rubén Durán, Professor, Department of Plant Pathology, Washington State University, Pullman 99164; Phytopathology 70:528-533. Accepted for publication 4 December 1979. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-528.

When primary basidiosporic lines of T. aegopogonis were used to inoculate seedlings of Aegopogon tenellus, some unpaired lines of the fungus sporulated in the ovaries of the host. Such lines were self-fertile, heterokaryotic for mating type, and homothallic. Primary basidiospores from which they were derived invariably were multinucleate and did not fuse, but when they germinated some formed infection hyphae with conjugately associated nuclei, either in situ or after abstricting from promycelia. Such heterokaryotic lines readily dissociated in shake cultures and formed secondary mononucleate basidiospores of two mating types. Other unpaired primary lines, however, did not form infection hyphae or sporulate in the ovaries, and, hence, were self-sterile, homokaryotic for mating type, and were shown to be heterothallic by pathogenicity and incompatibility tests. Homokaryotic lines also dissociated in shake cultures and formed secondary mononucleate basidiospores of one or the other mating type, but not of both. When secondary mononucleate lines of either source or primary homokaryotic lines of different mating types were paired, they formed infection hyphae and sporulated in the ovaries. Homothallism was attributed to the presence of nuclei of both mating types in some primary basidiospores, heterothallism to the presence of only one type in others. Nuclei in promycelia outnumbered basidiospores produced by about 5:1. The multinucleate condition of primary basidiospores was thus a normal and presumably inevitable consequence. Basidia averaged 32.00 nuclei, 6.54 basidiospores, and the latter 4.89 nuclei. Migration of mating type nuclei to the basidiospores appeared to be nonrandom, since homokaryotic basidiospores were isolated more frequently than could be accounted for by Chi-square tests.