STUDIES OF CANADIAN THELEPHORACEAE: XI. CONIDIUM PRODUCTION IN THE THELEPHORACEAE

Abstract

Four species of the Thelephoraceae, Stereum sulcatum Burt, Vararia granulosa (Pers. ex Fries) Laurila, Corticium furfuraceum Bres., and Trechispora raduloides (Karst.) Rog. have been found to produce conidia on both simple-septate, haploid mycelia and clamp-bearing dicaryotic mycelia. The conidia of the first three species are borne on oedocephaloid conidiophores while those of the fourth are formed sympodially. In all four species, the conidia, whether produced on haploid or dicaryotic mycelia, are uninucleate and each germinates to give a simple-septate, haploid mycelium. Interfertility tests were undertaken with monosporous cultures derived from the germination of single conidia or of single basidiospores. By pairing single basidiospore cultures from an individual fruit body of both Stereum sulcatum and Vararia granulosa, it was shown that these species exhibit a bipolar type of interfertility. For each of the species under investigation, complete interfertility was obtained in pairings between single conidium cultures from different isolates of the same species. A series of single conidium cultures for each species, derived from conidia borne on a dicaryotic mycelium, when paired in all possible combinations, fell into two groups on the basis of their ability to produce clamp connections. In S. sulcatum, members of each group of single conidium cultures were interfertile with one or other of the two types of single basidiospore cultures from the same isolate. Cytological studies show that there is no fusion of nuclei prior to conidium formation on the dicaryotic mycelium. Instead, the two nuclei of the dicaryon divide separately to produce approximately equal numbers of each type of nucleus, one of which enters each conidium. As indicated by the interfertility tests, the conidia therefore contain nuclei of two reaction types which are identical with those of the two nuclei of the dicaryon and also with those of the nuclei of the parent basidiospores.