What is cultivated oyster mushroom? Phylogenetic and physiological study of Pleurotus ostreatus and related taxa

The wild and cultivated isolates of Pleurotus ostreatus were the subject of a phylogenetic analysis, AMOVA of DNA sequences, exact test of population differentiation, estimation of evolutionary divergence, and cardinal temperature measurement. Two significantly genetically separated groups (OA and OB) with limited mutual gene flow were revealed. While OA is identical with P. ostreatus sensu stricto and includes mainly wild isolates, OB is a more genetically variable group of cultivated isolates of unclear geographical origin. The delimitation of the two groups is confirmed by three genetic markers (ITS, TEF1 and RPB2 ). Limited gene flow between those two groups was detected, but this is comparable to the putative gene flow between OA, OB on the one hand and P. eryngii and P. pulmonarius on the other. This gene flow between OA and OB may be caused by artificial breeding activities, but the number of such hybridisation events is limited. The genetic differences are also confirmed by the different growth rates of the two groups. The centre of distribution of P. ostreatus s. s. is in Eurasia, while the origin of the OB group is unknown. The availability of a validly published taxonomic name for OB is discussed.