Mating and fruiting studies of Auricularia delicata and A. Fuscosuccinea

Single-spore isolates were obtained from three collections of Auricularia delicata from the People's Republic of China and five collections of A. fuscosuccinea: one each from the Northern Marianas Islands, Ryukyu Islands and Florida, and two from Brazil. A typical bifactorial pattern was observed in self-crosses of one of the A. delicata stocks and in the A. fuscosuccinea stocks from the Northern Marianas Islands and Florida. In these stocks, nuclear migration was not observed in A=#B crosses and false-clamped mycelia derived from A#B= crosses were stable. Mating patterns could not be determined in the remaining five stocks. Where reactions occurred, few true clamps and mostly false clamps were observed. The reason for the reduced ability or inability of these stocks to cross is believed to be due to the length of time that the basidiocarps had been dried prior to obtaining spore deposits. All combinations of interstock crosses of A. delicata, and the Northern Marianas Islands x Ryukyu Islands and Brazil x Brazil crosses of A. fuscosuccinea were compatible and typical basidiocarps developed from dikaryons. The Florida stock was intersterile with all other stocks, and those from the Northern Marianas Islands and Ryukyu Islands were intersterile with those from Brazil. Intersterile reactions were characterized by a zone of aversion, at the contact zone, where the monokaryons grew together. Fruiting studies indicate that the presence/absence of the medulla in Auricularia and the merulioid to porose-reticulate hymenium in A. delicata are inherent characteristics and not environmental modifications. However, the basidiocarp color was more variable in A. fuscosuccinea than described in the literature. Lowy (1951) redefined species concepts in Auricularia Bull.: Merat using cross sectional morphology of the basidiocarp in place of traditional characteristics, such as size, shape and color of the basidiocarp. The traditional characteristics were considered by Lowy (1951) to vary with the age of the basidiocarp and environmental conditions, whereas he believed the internal anatomy of the basidiocarp to be little affected by these factors. The characteristics emphasized by Lowy (1951) in defining species were the presence/absence, width and morphology of the medulla, and length of the abhymenial hairs. These features are presently used in defining species in the genus. Although Lowy believed the traditional characters to be quite variable, he did not consider them without value. In describing Auricularia delicata (Fr.) Henn. and A. fuscosuccinea (Mont.) Farl., Lowy (1952) utilized traditional characteristics in addition to morphology in cross section. In his description of A. delicata, Lowy (1952) described the characteristic merulioid to porose-reticulate hymenium as, "being the most striking macroscopic feature by which the species may be safely identified." In A. fuscosuccinea, Lowy (1952) described fresh specimens as, "distinctly rosy to vinaceous," and stated that, "In the fresh state this species is not likely to be confused with any other." These characteristics have also been emphasized by more recent students of this genus (e.g., Cheng and Tu, 1978; Kobayasi, 1981).