Comparative Morphology, Intracompatibility, and Interincompatibility of Several Species of Exidiopsis (Exidiaceae)

Intracollection pairings of single spore isolates demonstrated that Exidiopsis calcea, E. grisea, E. effusa, E. plumbescens, and three undescribed species of Exidiopsis are bifactorial. Selected mating types of these species were paired in all possible combinations; mating types of two stocks of E. plumbescens representing partially interincompatible populations of this species were included in these interspecific pairings. Clamp connections were not detected in any interspecific pairing. The contact zones of all interspecific pairings varied in morphology; however, they were, in general, more distinct than the contact zones of intraspecific, compatible pairings. Often an obvious line of aversion was formed in the contact zones of the interspecific pairings resulting in distinct hyphal ridges. Frequently these ridges grew together in 5 wk to form a mound-like zone between the two strains. A brownish, water soluble pigment was evident in many of the interspecific pairings and in a few of the intraspecific pairings. The three undescribed species, E. paniculata, E. diversa, and E. punicea, are described and illustrated.