MOLECULAR SYSTEMATICS OF E-STRAIN MYCORRHIZAL FUNGI - WILCOXINA AND ITS RELATIONSHIP TO TRICHARINA (PEZIZALES)

Nuclear-encoded ribosomal RNA gene sequences (rDNA) spanning 107 base pairs at the 3' end of the 18S gene, the 5' internal transcribed space r region (ITS1), and across divergent domain DI near the 5' end of the 28S gene were analyzed to infer a phylogeny for taxa of the E-strain mycorrhizal fungal genus Wilcoxina and to determine their relationship to representatives of the genus Tricharina. The phylogeny suggests th at Wilcoxina and Tricharina, although related, should be maintained as separate genera. Wilcoxina taxa formed a distinct group that exhibite d interspecific variation of 37.6% in the ITS1 region. Wilcoxina alask ana was the most distant taxon, which is consistent with its growth on an unusual substrate (rotting wood). It remains to be confirmed that this taxon is mycorrhizal. A cryptic Wilcoxina species, known only fro m root isolates, was found. Sequence analysis of the ITS1 region disti nguished two varieties of Wilcoxina mikolae: var. mikolae and var. tet raspora. Among the taxa of Tricharina examined there was 31.2% variati on in the ITS1 region. The most divergent taxon in the Tricharina grou p was Tricharina praecox,; although sequence analysis was unable to di stinguish the varieties described within this species. The remaining t axa in Tricharina formed a tight group with only 10.2% interspecific d ivergence in the ITS1 region. There is sequence evidence that at least two taxa are included in Tricharina gilva as presently delineated. As the sole report of mycorrhiza formation in Tricharina is shown to be based upon a misidentification, it therefore appears that only Wilcoxi na taxa are mycorrhizal.