Evidence for two independent lineages of shiitake of the americas (Lentinula boryana) based on rDNA and beta-tubulin gene sequences.

Portions of ribosomal RNA genes (rDNA) were sequenced from members of the genus Lentinula and were used, along with partial beta-tubulin gene sequences, for phylogenetic reconstructions. The rDNA sequences of L. boryana were separated into two well-defined lineages. Lineage 1 was composed of isolates from Mexico and Costa Rica while lineage 2 encompassed isolates from the United States, Venezuela, and Brazil. The two South American isolates of L. boryana had nearly identical ITS sequences and very closely related beta-tubulin sequences. This high level of similarity may indicate that sexual reproduction occurs among the sampled populations, although this is difficult to reconcile with the large geographic distances (over 4000 km) that separate some of the collecting locations. An alternative explanation may be that the isolates sampled are the product of a rapid population expansion over a large geographic area. Analyses of partial beta-tubulin gene sequences that were rooted using Pleurotus spp. support the hypothesis that L. boryana is monophyletic.