Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Isolation and identification of the causal agents of root and crown rot of pistachio trees in the Sistan and Baluchistan provinces.

Abstract

Pistachio is the most important commercial product in Iran and root and crown rot (gummosis) is the most serious diseases of this crop. The causal agents of the disease were unknown in Sistan and Baluchistan provinces, where 5000 ha are under pistachio cultivation. During 2002-2003, 30 pistachio orchards, including pistachio trees of different ages, were inspected throughout the seasons. Eighteen Phytophthora isolates were isolated using citrus leaf pieces as baits on water-saturated soils collected from around the infected trees and cultured on PARPH medium. Some isolates were obtained from surface-disinfected tissues of trees infected with root and crown disease. Two groups of isolates were obtained. Based on the morphological and physiological characteristics of the Sistan and Baluchistan pistachio isolates, the first group of isolates was identified as Phytophthora pistaciae sp. nov., whereas the second group was identified as P. nicotianae. The two Phytophthora species were confirmed to be using the unripe pear and apple fruit inoculation method, detached pistachio twig inoculation method, and inoculated vermiculite method to infect the pistachio scions through the root area and artificial inoculation of the crown area with a plug of cultured isolate medium. This is the first report of pistachio tree gummosis, and its causal agents from Sistan and Baluchistan provinces.