Occurrence of grapevine trunk diseases caused by fungal pathogens in the domestic and overseas

Abstract：Grapevine trunk diseases (GTDs) are mainly associated with trunk necrosis, cankers and diebacks, and lead to whole plant death in severe cases. GTDs are one of the most virulent diseases on grapevine that affect the yield and quality significantly. To date, there are five fungus-related GTDs re-ported in the world (Esca disease complex, Black foot disease, Botryosphaeria dieback, Eutypa dieback and Diaporthe dieback), and three of them including Botryosphaeria dieback, Eutypa dieback and Dia-porthe dieback have been reported in China. Esca disease complex was first reported on grapevine in France in 1865. It causes serious economic losses in many grape-growing countries and regions, espe-cially in Europe. The average incidence of Esca disease complex had increased to 32.6% in many ma-ture vineyards of central-eastern Italy from 2005 to 2007. The symptoms of Esca disease complex in the field vary with the grape variety, the age of the vine and the affected plant part. To date, there are 48 pathogenic fungi associated with Esca disease complex including Phaemoniella chlamydospora, Phaeo-acremonium spp., Cadophora spp., and some basidiomycetes (Coprinellus spp., Fomitiporia spp., Fomi-tiporella spp., Inocutis spp., Phellinus spp. and Stereum spp.). Black foot disease (BFD) is one of the most significant GTDs, especially for nurseries and young plantations. It was first reported on grape- vine in France in 1961. In the Czech Republic, about 30% of plants showed root necrosis, reduced root biomass, and wood necrosis in the basal ends of the rootstock, which are typical symptoms of BFD that  appear after one year of cultivation in 2015. The typical symptoms of this disease can be of external symptoms such as delayed or absent budding in the nurseries, stunted growth, shortened internodes with small-sized trunks in new plantations, and chlorotic leaves with necrotic margins in the field, and inter-nal symptoms such as brown to black necrosis on the base of the rootstock and sunken necrotic root le-sions of the root hairs. To date, there are 32 fungal species associated with BFD in the world including the species belonging to Campylocarpon, Cylindrocarpon, Cylindrocladiella, Dactylonectria, Ilyonec-tria, Neonectria, Pleiocarpon and Thelonectria. Botryosphaeria dieback was first reported on grapevine in Canada in 1964. It occurs in most of the grape-growing regions, and the incidence of Botryosphaeria dieback varies with different grape-growing countries. The typical symptoms of this disease include the dieback of the branches or trunks, brown to black wedge-shaped or arc-shaped necrotic spots on a cross- section of the trunk, fruit rot, bud necrosis, and whitish branches. To date, there are 44 pathogenic spe- cies associated with Botryosphaeria dieback in the world including species belonging to Botryosphaer-ia, Diplodia, Dothiorella, Lasiodiplodia, Neofusicoccum, Spencermartinsia and Sphaeropsis. In China, it was first reported in 2010 and caused cane or shoot cankers, fruit drop, wood cankers, and finally whole plant death. The incidence of Botryosphaeria dieback varies in different regions. The incidence is 3%-8% in general areas, but can be as high as 10%-20% in severe areas such as Guangxi and Zhejiang provinces, China. The pathogenic fungi that cause Botryosphaeria dieback in China mainly include Bot-ryosphaeria dothidea, Diplodia seriata, Lasiodiplodia theobromae, Neofusicoccum parvum, Lasiodiplo-dia pseudotheobromae and Neofusicoccum mangiferae. Eutypa dieback was first reported on grapevine in Australia in 1973. The diseased plants showed shortened internodes, yellowing and wilting between the veins on leaves, and wedge necrosis in the trunk. The diseased leaves become cup-shaped and final-ly fall off. To date, there are 20 pathogenic fungal species associated with Eutypa dieback from Crypto-sphaeria, Cryptovalsa, Diatrype, Diatrypella, Eutypa and Eutypella genera. Eutypa lata has a wide dis-tribution and is the main causative agent of the Eutypa dieback in most grape-growing areas. Eutypa die-back was first reported in China in 2007 and resulted in shortened internodes, faded and yellowed leaves, and the wedge-shaped, grey to brown necrosis on the trunk. Eutypella vitis is reported as patho-gen in China, however, but has not been proved by Koch’s postulates. The incidence of Eutypa dieback in different grapevine cultivars and vineyards is still unknow. Diaporthe dieback was first discovered in the United States in 1909. During the initial stage of the disease, red to brown spindle-shaped necrosis develops in the trunk, and later the diseased spots gradually expand, showing dark brown necrosis. To date, there are 27 Diaporthe species associated with Diaporthe dieback in the world. The pathogenic fungi that cause Diaporthe dieback vary with different countries, and there is more than one pathogenic agent in each country. In China, it was first reported in 1998, and the diseased plants showed dark brown necrosis on the trunk. The pathogenic fungi that cause Diaporthe dieback in China mainly in-clude Diaporthe eres, Diaporthe guangxiensis, Diaporthe gulyae, Diaporthe hongkongensis, Diaporthe hubeiensis, Diaporthe pescicola, Diaporthe phaseolorum, Diaporthe sojae, Diaporthe unshiuensis and Diaporthe viniferae. This paper focuses on the distribution, field symptoms and fungal pathogens of GTDs around the world, and provides useful information on the status of GTDs in China, providing a reference for accurate diagnosis, identification and control of GTDs in the future.