Morphological and molecular characterization of Oomycetes associated with root and crown rot of cucurbits in Kermanshah province, Iran

Pythium and Phytophthora are among the most well-known plant pathogens around the world that cause rotting of seeds, root, and crown, seedling death, and soft rot of fruits in contact with the soil. In this research, 347 isolates of these two genera and their close genus, Phytopythium were isolated from the cucurbits fields in Kermanshah province, Iran and examined in terms of morphological and physiological characteristics. ITS-rDNA region and the partial cytochrome oxidase II (cox II) gene from the selected isolates were amplified and sequenced to confirm the morphological identification. Based on the morphological, morphometrical, physiological, and phylogenetic examinations, nine species of Pythium including P. aphanidermatum, P. dissotocum, P. catenulatum, P. kashmirense, P. middletonii, P. nodosum, P. oligandrum, P. torulosum, and P. ultimum; two species of Phytopythium including Pp. mercuriale and Pp. litorale, and three species of Phytophthora including Ph. melonis, Ph. nicotianae, and Ph. parasitica were detected. Among the species identified in this study, Pp. mercuriale was a new record for mycobiota of Iran and two species, P. aphanidermatum and P. ultimum were isolated more frequently.