Identification and pathogenicity of fungal species associated with grapevine trunk diseases in Khorasan–Razavi province, Iran

Grapevine trunk diseases (GTDs) are the most important factors in crop reduction and cause considerable economic problems in grapevines worldwide. From 2016 to 2018, several field surveys were conducted on numerous vineyards in Khorasan– Razavi province to study fungal species associated with grapevine trunk diseases. In this study, samples were collected from the trunk and branches of trees showing yellowing, stunted growth, dieback and wood discoloration in cross–sections. In this study, 258 fungal isolates were obtained and identified based on morphological characteristics and comparison of DNA sequence data (ITS–rDNA region and a part of β– tubulin gene). These isolates were identified as Phaeoacremonium minimum (75 isolates), P. parasiticum (19 isolates), P. iranianum (52 isolates), P. tuscanum (8 isolates), Fomitiporia mediterranea (56 isolates) and Seimatosporium vitis (48 isolates). Pathogenicity of the selected isolates was verified by inoculation of potted grapevines shoots under greenhouse conditions. Based on the mean length of wood discoloration in the wood, P. minimum and F. mediterranea were the most and least virulent species, respectively. Our findings indicated that known fungal trunk pathogens such as Phaeoacremonium species and F. mediterranea occur on grapevine in Khorasan–Razavi province. This study is the first report of S. vitis associated with grapevine decline in Iran.