Phylogenetic analysis of the Glomeromycota by partial β-tubulin gene sequences
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The 3’ end of the β-tubulin gene was amplified from 50 isolates of 45 species in Glomeromycota. The analyses included a representative selection of all families except Pacisporaceae and Geosiphonaceae. Phylogenetic analyses excluded three intron regions at the same relative positions in all species due to sequence and length polymorphisms. The β-tubulin gene phylogeny was similar to the 18S rRNA gene phylogeny at the family and species level, but it was not concordant at the order level. Species in Gigasporaceae and Glomeraceae grouped together but without statistical support. Paralogous sequences in Glomus species likely contributed to phylogenetic ambiguity. Trees generated using different fungal phyla as out-groups yielded a concordant topology. Family relationships within the Glomeromycota did not change regardless if the third codon position was included or excluded from the analysis. Multiple clones from three isolates of Scutellospora heterogama yielded divergent sequences. However, phylogenetic patterns suggested that only a single copy of the β-tubulin gene was present, with variation attributed to intraspecific sequence divergence.
KeywordsGlomeromycota Beta-tubulin Phylogeny Arbuscular mycorrhizal fungi
The authors wish to thank Bill Wheeler, Robert Bills, and Sonia Purin for help with spore extraction and RFLP analysis. Funding was provided by a Fulbright scholarship to Zola Msiska and National Science Foundation grants DBI0650735 and DEB0649341 to Joseph Morton.
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