Phylogenetic analysis of Pleurotus species based on the nuclear SSU rRNA sequences

The internal regions of nuclear small subunit rRNA from 6 Pleurotus species and 5 Pleurotus ostreatus strains were amplified by PCR and sequenced. The DNA sequences of 8 Pleurotus strains (P. ostreatus NFFA2, NFFA4501, NFFA4001, KFCC11635, P. florida, P. sajor-caju, P. pulmonarius, and P. spodoleucus) were identical, but P. cornucopiae differed from them in two bases out of 605 bases. However, phylogenetic analysis of the sequences by DNA-distance matrix and UPGMA methods showed that P. ostreatus NFFA2m1 and NFFA2m2, known as mutants of P. ostreatus NFFA2, belonged to another group of Basidiomycotina, which is close to the genus Auricularia. The difference of the SSU rDNA sequences of P. cornucopiae from other Pleurotus species tested corresponds to the difference of mitochondrial plasmid type present in Pleurotus species as observed by Kim et al. (1993, Korean J. Microbiol. 31, 141-147).