Systematics in the genus Clavicorona (Basidiomycotina, Fungi): Morphology, incompatibility and phenoloxidase isozymes

The genus Clavicorona includes about 12 species of wood-rotting basidiomycete fungi distributed worldwide. The purposes of this study were to explore the potential of cultural morphology, incompatibility tests and isozyme electrophoresis in combination with comparative fruitbody morphology to solve systematic problems in Clavicorona.;One hundred and five monokaryotic and/or dikaryotic isolates representing nine taxa of Clavicorona were obtained from China, Europe, Japan, New Zealand, North America and Puerto Rico. These nine morphologically based taxa include a newly proposed species from Japan and four species from New Zealand. Morphological descriptions of these nine taxa are presented based on macro- and micromorphological characters.;The potential value of cultural morphology and spot tests for phenoloxidase activity was analyzed. Culture mat morphology developed on PDA and MYG was useful for delimiting species Descriptions of culture mat morphology are furnished for each analyzed species. Spot test results showed that all Clavicorona species have laccase activity on at least one medium during development in culture. All tested species showed tyrosinase activity on PDA and MYG, but not on MA. These results indicated that laccase and tyrosinase spot tests may be characteristic for the genus and only of very limited value in separating species. Self-crosses of single-spore isolates revealed that seven of these nine taxa were governed by a homogenic bifactorial incompatibility system. Intercollection matings indicated that collections from the same morphospecies were either fully compatible or shared common mating type alleles, regardless of morphological variation, whereas collections from different morphospecies were completely incompatible. Morphological delimitation of species in this study is basically congruent with biological species in this genus. Partial compatibility, however, was found among allopatric populations in one species.;Electrophoretic analysis showed that extracellular laccase banding patterns were mostly simple and reproducible in the genus. Banding patterns were different between morphospecies but consistent within species, indicating that laccase electrophoresis may be of significance in the systematics of Clavicorona. In contrast, electromorphic patterns for tyrosinase were variable in certain species, but specific for others.;A final section summarizes the results from various methods for each species, and discusses the roles and validity of each method in the systematics of Clavicorona.