Molecular and morphological characterization of three new species of Pythium from Iran: P. ershadii, P. pyrioosporum, and P. urmianum

Abstract

Three new species of Pythium: P. ershadii, P. pyrioosporum, and P. urmianum from soils of various regions in Iran are described and illustrated. These species are morphologically distinct from all other known species. Pythium ershadii is morphologically characterized by pyriform ornamented oogonia and rarely production of pyriform oospores. Pythium pyrioosporum differs from other species of the genus by the production of pyriform oospores and smooth walled oogonia, oospores with a tapering elongation toward a hypogynous antheridium and intercalary hypogynous antheridia. Pythium urmianum is distinguished by the presence of intercalary hypogynous antheridia, smooth walled oogonia formed laterally on hyphae or on short side branches and peanut-shaped oospores. Phylogenetic relationships of these new taxa with other Pythium species were investigated using internal transcribed spacers rDNA and partial coxI sequence data. The three species reside in clade E1 and are separated from closely related species.

Key words:

• Oomycota
• Peronosporomycetes
• phylogeny
• Pythiaceae
• taxonomy

Acknowledgments

The authors thank Professor Walter Gams for valuable comments on the nomenclature of new taxa and Esmaeil Khaledi for assistance with molecular studies.