RIBOSOMAL-RNA SEQUENCE PHYLOGENY IS NOT CONGRUENT WITH ASCOSPORE MORPHOLOGY AMONG SPECIES IN CERATOCYSTIS SENSU-STRICTO

The genus Ceratocystis sensu stricto includes important fungal pathoge ns of woody and herbaceous plants. This genus is distinguished from sp ecies in Ceratocystis sensu late by the presence of Chalara anamorphs. Ascospore shape has been used extensively in delineating Ceratocystis taxa, which show a large variety of ascospore shapes. Sequence analys is of one region of the 18S ribosomal RNA subunit and two regions of t he 28S ribosomal RNA subunit showed that there was a majority of multi ple substitutions at nucleotide sites and that there was a low transit ion/transversion ratio, T = 0.72. Both of these results suggest that t hese are well established, old species. Ascospore morphology, for the most part, was not congruent with the molecular phylogeny, and the use of morphological characters may be misleading in the taxonomy of thes e species.