PhytophthoraSpecies Causing Root and Collar Rot of Pomegranate in Turkey

摘要

Pomegranate (Punica granatum) is an important fruit-tree at southwestern Turkey, as this region (Antalya and Mugla provinces) produces and exports the great majority of the pomegranate fruits of the country. Pomegranate orchards showing severe dieback and tree mortality in the region were surveyed to determine the role ofPhytophthoraspp. in symptom development. Root (from 51 trees) and soil (from 136 trees) samples were collected from symptomatic trees in 113 commercial pomegranate orchards, covering 170 ha. A total of 98 isolates were obtained from the roots of 19 trees and soil samples of 79 trees, using selective medium and soil baiting. Species isolated were identified by morphological characteristics and ITS sequencing. The most frequently isolated species wereP. nicotianae(37 isolates) andP. palmivora(26 isolates), followed byP. parvispora(14 isolates), P. inundata(six isolates), P. cryptogea(four isolates), P. niederhauserii(four isolates), P.taxon walnut (two isolates) andP. rosacearum(one isolate), and four unidentified species. Twelve orchards were infected with more than one species. Disease incidence and prevalence were 4.59% and 69.91%, respectively. Pathogenicity tests by soil infestation, revealed that the isolates caused root and collar rot, reducing root weights of pomegranate seedlings.Phytophthora palmivoraandP. nicotianaewere the most virulent species. This is the first report of any species other thanP. palmivoracausing root and collar rot of pomegranate trees worldwide.