MOLECULAR EVIDENCE SUPPORTS THE SEPARATION OF LENTINULA-EDODES FROM LENTINUS AND RELATED GENERA

Restriction polymorphisms in two regions of the ribosomal DNA (rDNA) repeat unit were examined in 18 strains of Lentinus, Neolentinus, Pleurotus, and the shiitake mushroom Lentinula edodes. The polymerase chain reaction was used to separately amplify the 18S rDNA and the region spanning the two internal transcribed spacers and the 5.8S ribosomal RNA gene. Amplified products were digested with a battery of 10 restriction endonucleases and the two data sets were subjected to cluster analysis. All strains of Lentinula edodes consistently exhibited identical restriction profiles that were distinct from those of the genera Lentinus, Neolentinus, and Pleurotus. The internal transcribed spacer region exhibited more variability than the 18S rDNA, giving distinctive profiles for two strains of Lentinus tigrinus and for one strain of Neolentinus lepideus. Similarity coefficients were clustered with the unweighted pair group method with arithmetic average, single-linkage method, and complete-linkage method. Results from cluster analysis of the two data sets were highly congruent and tree topologies were consistent irrespective of the clustering method used. The distinctiveness of the groups was further confirmed by computing for consensus trees and cophenetic correlation coefficients. Ribosomal DNA restriction polymorphisms support the placement of the strains examined in separate taxa.