Biogeography and Speciation in the Oyster Mushroom Pleurotus

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9408347 Vilgalys The oyster mushrooms, genus Pleurotus of the Basidiomycetes, are important as wood degrading fungi, and some species are choice edible mushrooms which are collected or cultivated in many countries. Professor Rytas Vilgalys of Duke University is studying the patterns of species differences in the genus throughout its worldwide distribution. Conventional taxonomic study of morphology and of mating systems is being combined with modern analyses of nuclear ribosomal gene sequences, using numerous samples collected from field trips and from colleagues. Laboratory growth studies will be performed to determine mating systems and the limits of intersterility groups. A simple yet ingenious "spore trapping" technique is also being employed, whereby petri dishes with several tester strains are exposed for 48 hours to the local spore rain and results of hyphal fusion monitored. Concurrent molecular analyses focus on DNA sequence data derived from the worldwide sample of Pleurotus. Results of the studies will help answer several questions relevant to speciation in fungi: (1) how old are different species groups, under a molecular clock model; (2) what are the genealogical or phylogenetic relationships among the species; and (3) what are the relationships between geographic distribution and levels of morphological, molecular, and mating system variability. By providing comprehensive taxonomic descriptions for each species from geographically diverse regions, the study will also provide a baseline for developing commercially useful strains of oyster mushrooms for cultivation and biotechnology.