Gnomoniopsis paraclavulata, a previously unrecorded causal agent of oak decline in Italy

Oak trees (Quercus pubescens) showing symptoms of twig and branch dieback, internal wood necroses, and decline, were surveyed in a public park located in Catania province (eastern Sicily, Italy). Gnomoniopsis-like fungi were consistently isolated from symptomatic wood tissues. Based on morphology and phylogenetic analyses of ITS, tef1 and tub2 loci, the fungi were identified as Gnomoniopsis paraclavulata. A pathogenicity test was conducted by inoculating stems of 1-year-old oak seedlings with mycelium plugs of a representative G. paraclavulata isolate. Three months after inoculation, internal necrosis around inoculation points and twig dieback were observed. Colonies of G. paraclavulata were reisolated from necrotic tissues of inoculated plants, fulfilling Koch’s postulates. This is the first report of G. paraclavulata causing dieback and decline on Q. pubescens trees.