Determination of Phytophthora Species, the Causal Agent of Pistachio Gummosis, and Their Distribution, Relative Incidence and Rate of Damage in Qazvin Province

Crown rot or gummosis is one of the most important diseases of pistachio trees in Qazvin province. For determination of Phytophthora species, their distribution and rate of damage in Qazvin province (Boeen Zahra region), samples from Crown tissue and soil were collected. In laboratory, isolation of fungus was performed by selective media (CMAPV and PARPH). The isolates were purificated by culturing tip of hypha and important morphological charactristics were studied to identify species. Two fungi, P. citrophthora and P. nicotianae were recognized as causal agents of gumosis in Boeen Zahra region and proved their pathogenecity. With repeated surveys from pistachio orchards in spring, summer and fall, observation of disease symptons and isolation of fungus from soil or tissue of infected trees, distribution of disease was determined in different area of Hosein Abad, Valad Abad, Arasang, Khonan, Jahan Abad and Eshrat Abad in Boeen Zahra region. Based on infection percentage of orchards, rate of gummosis damage in Boeen Zahra region was estimated very low and approximately 2-3 percent.