Phytophthora ilicis as a leaf and stem pathogen of Ilex aquifolium in Mediterranean islands

Abstract

Between 2010 and 2013 several English holly trees showing defoliation, leaf and twig blight were found in natural ecosystems in Sardinia and Corsica. A Phytophthora species was consistently isolated from necrotic tissues of leaves and twigs, and bleeding cankers on stems. Isolates obtained were identified as Phytophthora ilicis, on the basis of morphological features, colony patterns and growth rates at different temperatures. Identity was confirmed by sequence analyses of the ITS, β-tubulin and cox1 gene regions. Two different genotypes within P. ilicis were detected. Pathogenicity of P. ilicis isolates was verified by inoculating freshly cut twigs of English holly. Phytophthora ilicis was originally recorded on English holly in western USA, and to date has been found only in cool temperate regions in northern America and, more recently, in Europe. This is the first report of P. ilicis on English holly in the Mediterranean region. Two additional Phytophthora species were isolated from other trees and shrubs species growing together with English holly, including P. bilorbang from Alnus glutinosa leaves and P. pseudosyringae from rhizosphere soil samples of A. glutinosa and Castanea sativa, and from symptomatic leaves of Hedera helix