A Revision of Iranian Phytophthora drechsleri Isolates from Cucurbits Based on Multiple Gene Genealogy Analysis

Abstract

The plant pathogenic Phytophthora drechsleri is morphologically similar to some other non-papillate Phytophthora spp., especially P. melonis, and it is difficult to discriminate these convergent taxa. It seems that the Iranian pu tative P. drechsleri isolates from different cucurbit species have been generally misi dentified and their characteristics do not match with P. drechsleri. In order to compare these two groups, authentic P. drechsleri isolates and isolates from different cucurbits wer e assessed for morphological, physiological (cultural, temperature relations, mat ing type), and molecular traits. Multiple gene genealogy analysis were performed on regions of nuclear (ITS, β -tubulin, translation elongation factor 1 α , elicitin) and mitochondrial (cytochrome c oxidase subunit I) gene sequences. Congruence was observed in different phylogenetic data sets. The present study demonstrated that putative P. drechsleri isolates from cucurbits and pistachio trees were a distinct species and belonge d to P. melonis . Data showed that P. melonis was a homogenous species and there were no conside rable molecular intraspecific variations between isolates from cucurbits and isol ates from other hosts. Design of a molecular species-specific identification tool for P. melonis isolates is under investigation. Keywords: Internal transcribed spacer of rDNA , Phylogeny, Phytophthora melonis , Oomycota .