گزارش جدید از یک گونه Phytopythium برای فلور اوومیستی ایران

Phytopythium is a monophyletic genus of the Peronosporaceae and morphologically is intermediate between Pythium and Phytophthora. Most members of this recently established genus have already been classified in Pythium. Several species of Phytopythium are distributed worldwide and are found in various water and terrestrial ecosystems of tropical, temperate and cold regions. Some species are saprobes in natural environments but a few taxa such as Pp. helicoides and Pp. vexans are well known as plant pathogens causing root and stem rot under conducive conditions. Therefore, considering the damage of some species to field and greenhouse crops, Phytopythium is considered as an agriculturally important genus. To identify Phytopythium species in central regions of West Azarbaijan province, soil samples were collected from these regions in 2016 and 2017. Isolation was performed using baiting technique and baits were cultured in selective medium. The isolates were purified by taking hyphal tips growing on 2% water-agar and transferring them onto cornmeal agar. Morphological identification was performed by culturing the purified isolates in sterile distilled water containing autoclaved wheat leaves and examining morphological characters of asexual and sexual organs. Furthermore, to confirm the results of morphological studies and more precise identification of the species, ITS1-5.8S-ITS2 regions and partial mitochondrial COXI gene in the isolates were amplified and sequenced and, their phylogenetic relationships with described species of the genus were investigated. Based on the morphological characters and phylogenetic analyses of DNA sequences, three species including Pp. vexans, Pp. ostracodes and Pp. carbonicum were identified. Among the identified species, Pp. ostracodes is new for West Azarbaijan province and Pp. carbonicum is new for oomycete flora of Iran.