Identification of Pistachio Root and Crown Rot Casual Agents in Sistan-Baluchistan Province

Pistachio is the most important commercial product in Iran and root and crown rot (gummosis) is the most serious diseases of this crop. Causal agents of the disease were unknown in Sistan -va- Baluchistan province where 7000 ha are under cultivation of pistachio. During 2 years, thirty pistachio orchards including pistachio trees of different ages were inspected throughout different seasons. Eight Phytophthora isolates were isolated using citrus leaves pieces as baits on water-saturated soils collected from around the infected trees and cultured on PARP medium. Some isolates were isolated culturing the surface disinfected tissues of root and crown of infected trees directly on PARP as the semi-selective medium too. Two groups of isolates were obtained. Based on the morphological and physiological characteristics of the Sistan -va- Bluchistan pistachio isolates, the first group of isolates was identified as Phytophthora pistaciae and the second group identified as Phytophthora nicotianae. The two Phytophthora species were found pathogens using unripe pear and apple fruit inoculation method, detached pistachio twigs inoculation method and artificial inoculation of the crown area with a plug of cultured isolate medium. This is the first report of incidence of pistachio tree gummosis and its causal agents from Sistan -va- Baluchistan province.