Molecular characterization of Embellisia and Nimbya species and their relationship to Alternaria, Ulocladium and Stemphylium

Abstract

DNA sequences from rDNA and protein-coding regions were determined for six Embellisia and two Nimbya spp. and were compared to those from Alternaria, Ulocladium and Stemphylium spp. Sequences determined included rDNA from the nuclear internal transcribed-spacer region (ITS1/5.8S/ITS2) and the mitochondrial small-subunit (mt SSU) and a portion of the glyceraldehyde-3-phosphate dehydrogenase (gpd) gene. Phylogenetic analyses were performed on each dataset separately and then combined for total evidence analysis using methods of maximum parsimony and maximum likelihood. Results revealed that Embellisia and Nimbya clustered within a large monophyletic Alternaria-Nimbya-Embellisia-Ulocladium clade with Stemphylium as the sister taxon. Members of the infectoria species-group were the most basal group in this large polygeneric clade. Embellisia and Nimbya were sister taxa of the remaining Alternaria and Ulocladium spp. and were related more closely to Alternaria than was Stemphylium. Four Embellisia spp. formed a monophyletic clade. However, E. allii clustered with the two Nimbya spp. and E. indefessa clustered with Alternaria and Ulocladium spp., revealing that Embellisia, as currently circumscribed, is polyphyletic. Potential revisions of taxonomy for all genera are discussed.

• gpd
• ITS
• maximum likelihood
• mitochondrial SSU
• parsimony
• phylogeny

The authors wish to thank Patricia Figuli and Craig Michoski for their assistance in PCR amplification of target sequences. A Faculty Small Grant Award, College of Agriculture and Life Sciences, University of Arizona, supported this research.