Tilletia Lycuroides, Another Homo-Heterothallic Bunt Fungus

Abstract

When primary basidiosporic lines of Tilletia lycuroides were tested for pathogenicity, most unpaired lines sporulated in the ovaries of Lycurus phleoides. Such lines were selffertile, heterokaryotic for mating type, and homothallic. Heterokaryotic lines dissociated in shake cultures and formed secondary mononucleate basidiospores ofa, and a2 incompatibility. Some unpaired lines, however, were self-sterile, homokaryotic for mating type, and shown by pathogenicity tests to be heterothallic. When one of these dissociated, secondary basidiospores of only one mating type were formed. Homothallism was attributed to the presence of nuclei of both mating types in most primary basidiospores, heterothallism to the presence of only one type in others. Pathogenicity tests were required to identify self-fertile lines and to determine the incompatibility factors of secondary lines. I proved (2) Tilletia aegopogonis R. Duran is homo-heterothallic by inoculating Aegopogon tenellus (DC.) Trin. with cultures from single primary basidiospores, and, then, with secondary basidiospores, thus completing the life cycle. Primary basidiospores of the fungus were typically multinucleate and contained nuclei of both mating types which explained why they were solopathogenic and did not fuse. But when the self-fertile primary basidiospores dissociated in shake cultures they formed secondary mononucleate basidiospores of two mating types which required pairing to complete the life cycle. Previously, the nuclear condition of basidia of Tilletia species, and their relationships to disease cycles, was mostly inferred from the wheat bunt fungi [Tilletia caries (DC.) Tul. and Tilletiafoetida (Wallr.) Liro] in which primary basidiospores are mononucleate, homokaryotic for mating type, and strictly heterothallic.