Interfertility and Comparative Morphological Studies of Exidiopsis Plumbescens from the West Coast

ABSTRACT

Single basidospore isolates were obtained from 16 collections of Exidiopsis plumbescens from northern California, western Washington, and the vicinity of Vancouver, British Columbia, Canada. Intracollection matings indicate a bifactorial compatibility pattern; intercollection matings were all interfertile except those with common B factors. Thirty-two A factors and 27 B factors were identified. No evidence was obtained of nuclear migration in A≠B≠ matings; evidently the dikaryon is formed only in the contact zones of compatible crosses. A≠B= crosses resulted in a relatively unstable heterokaryon with false clamps, binucleate, terminal hyphal segments, and uninucleate, subterminal segments. Both A=B≠ and A=B= crosses yielded hyphae with simple septa and, predominately, uninucleate, hyphal segments. The 28 specimens studied in detail, including the 16 used in the interfertility studies, varied in macroscopic aspect when collected and when dried, thickness of basidocarp, morphology and size of basidia, and size of basidiospores. Exidiopsis plumbescens occurs on a variety of decaying woods, but all verifiable records were from woody, angiosperm species. The means of the length and width of the basidiospores formed a linear relationship. No consistent correlations were observed in the larger samples between basidiospore size or morphology and substrate or collection site. The dimensions of the spores of the collections used in the interfertility tests were evenly distributed throughout the range of spore sizes. Interfertility and traditional morphological studies provide a basis for determining the interbreeding populations (i.e., species) of some taxa of the saprobic Heterobasidiomycetes.

Key Words:

• Exidiopsis plumbescens
• bifactorial compatibility
• basidiospore variability
• nuclear migration