The current status of Pythium species in Iran: challenges in taxonomy

Pythium species are cosmopolitan, fungus-like oomycotes which may cause diseases in plants, animals and even human beings. Some of the species, however, are saprophytes and also well-proven biological control agents of plant pathogenic fungi. Since 1968, when the first Pythium species was reported from Iran, ca 44 species, two varieties, and five groups of this genus have been reported from different regions of Iran. Nevertheless, morphological or morphometric characters of only 35 species are more or less described. On the other hand more than 50% of these species have only been reported once. In the course of identification and classification of Pythium taxa in Iran, in addition to general obstacles, there exist some other problems. The lack of identification keys for the species; the absence of comprehensive checklists of the species, their dispersal and matrices; the lack of or the inadequacy of  the species descriptions; unillustrated descriptions; generalization about the host names; unspecific geographical locations; unknown isolation matrices; the absence of type specimens in type culture collections; and the overlooking of molecular analyses, especially in the case of phylogenetic species are some of the challenges ahead. In this review, the prospects of future studies on the taxonomy of the Pythium species in Iran and the proposed solutions for the taxonomic challenges are discussed.