Characterization of fungal pathogens associated with grapevine trunk diseases in Washington State

Leslie A. Holland

Grapevine (Vitis vinifera) trunk diseases are a threat to wine grape productivity worldwide. Symptoms of trunk cankers and associated dieback have been observed in Washington vineyards for many years. However, the only study of such diseases in Washington State was completed nearly 40 years ago, and that study focused on ‘Concord’ grapevines (Vitis labrusca) rather than wine grapes. The present study is the first since then to characterize the fungal pathogens associated with grapevine trunk diseases in Washington State, and the first to focus on trunk diseases of wine grapes in the region. Surveys of four selected vineyards revealed incidence of foliar and trunk symptoms for each vineyard (from 16- to 42-years old) surveyed ranged from 2.8 to 33%. Fungi were isolated from symptomatic grapevine wood from seven commercial vineyards in the Yakima Valley and Horse Heaven Hills American Viticultural Areas. Samples of symptomatic wood were collected in June 2014 and fungi were isolated on Potato Dextrose Agar (PDA) supplemented with 100 ppm streptomycin sulfate, incubated at 20°C. Culture morphology, conidiogenous cell and conidium morphology were used to characterize isolates. Internal transcribed spacer (ITS) region sequences of the nuclear ribosomal DNA (rDNA) were obtained for 107 isolates. Partial sequences for the [beta]-tubulin (BT) gene were obtained for 38 isolates, and partial sequences for the elongation factor – 1 [alpha] (EF-1[alpha]) gene were obtained for 7 isolates. Results revealed that the isolates included seven fungal species associated previously with grapevine trunk diseases, including Cryptosphaeria pullmanensis, Diaporthe eres, Diatrype whitmanensis, Diplodia mutila, Diplodia seriata, Eutypa lata, and Eutypa laevata. Species of Diatrypaceae were the fungi most commonly isolated, followed by species of Botryosphaeriaceae. Other species commonly isolated but not demonstrated to cause cankers in grapevine included Cytospora rhodophila, C. chrysosperma, Discostroma fuscellum, and Coniolariella limoniispora. This study provides new information about the diversity of fungal pathogens associated with grapevine trunk diseases in Washington State and the basis for future work to improve the diagnosis of grapevine diseases in the region.

Characterization of fungal pathogens associated with grapevine trunk diseases in Washington State

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