Investigation on occurrence status and types of grapevine trunk diseases in China

【Objective】Grapevine trunk diseases (GTDs) refer to a complex of fungal diseases that primarily damage grapevine wood. Currently, five major fungal- associated GTDs have been reported worldwide: Esca, Black foot disease, Botryosphaeria dieback, Eutypa dieback, and Phomopsis dieback. In China, Eutypa dieback was first reported in 2007, followed by subsequent discoveries of Botryosphaeria dieback, Phomopsis dieback, Black foot disease, and Esca. In recent years, grapevine trunk diseases have emerged as a major limiting factor hindering the healthy development of China's grapevine industry. However, there remains a lack of systematic and comprehensive understanding regarding the incidence, geographical distribution, pathogen composition, and severity of grapevine trunk diseases across China's various grape-growing regions. This study aims to clarify the main symptoms, types, distribution, and occurrence characteristics of GTDs in China, thereby providing a scientific basis for the formulation of effective disease management strategies.【Methods】From 2020 to 2024, field surveys were conducted in 74 vineyards in 17 provinces (Beijing, Hebei, Yunnan, Ningxia, Shanxi, Shaanxi, Henan, Heilongjiang, Guangxi, Xinjiang, Hubei, Jiangsu, Jilin, Shandong, Gansu, Liaoning, and Fujian), thereby covering the major grape- producing regions in China. Investigations were carried out during spring and autumn when the typical symptoms of GTDs were observed easily. Using the five-point sampling method, five points were randomly selected in each vineyard, with at least 100 vines inspected per point. Plants showing symptoms such as dead vines, weak growth, delayed development, yellowing or reddening leaves, small leaves, and poor root development were recorded as suspected GTDS cases. The total number of plants and diseased plants were recorded, and the disease incidence was calculated using the formula: Incidence/% = (Number of diseased plants / Total plants) × 100. A total of 177 typical symptomatic samples were collected from various vineyards. For pathogen isolation, tissue fragments (4-5 mm) were taken from the margin between necrotic and healthy tissues, surface- sterilized with 75% ethanol for 30 s, rinsed three times with sterile water, dried on sterile filter paper, and placed on potato dextrose agar (PDA) plates. After incubation at 25 ℃ for 5-7 days, hyphal tips were transferred to new PDA plates and isolates were purified by single-spore isolation. Preliminary morphological identification was based on colony characteristics, hyphae, and spores. DNA was extracted from purified isolates, and species identification was performed using ITS sequencing with primers ITS4/ITS5. The distribution and characteristics of GTDS occurrence across regions were analyzed based on isolation results.【Results】The main disease symptoms of GTDs observed in the field include plant mortality and vine decline, frequently accompanied by leaf abnormalities, impaired fruit development, and vascular discoloration. The average disease incidence ranged from 3.3% to 27.2%, exhibiting significant regional variations. Higher incidence rates were recorded in Shanxi, Beijing, Ningxia, and Yunnan, while the lowest was found in Shandong. All five major GTDs were present in China, and Botryosphaeria dieback, Black foot disease and Phomopsis dieback are the most prevalent types. Their distributions varied regionally: Botryosphaeria dieback was the most widespread, occurring in 14 provinces/municipalities except Liaoning, Jilin, and Gansu; Black foot disease was found in 11 provinces, excluding Fujian, Hubei, Jiangsu, Jilin, and Shandong; Phomopsis dieback was detected in 8 provinces; Esca was only observed in 6 northern provinces (Hebei, Ningxia, Shanxi, Xinjiang, Heilongjiang, and Jilin); and Eutypa dieback was identified only in Beijing. The diversity of GTDs types also varied significantly among regions, with complex disease compositions (involving four GTDs types) found in Beijing, Hebei, Shanxi, Heilongjiang, and Ningxia. Pathogen isolation and identification from 177 samples yielded 570 fungal isolates associated with GTDs, accounting for 52% of all isolates and belonging to 13 genera. Fungi associated with Botryosphaeria dieback included Botryosphaeria, Lasiodiplodia, Neofusicoccum, and Diplodia; those related to Black foot disease included Ilyonectria, Dactylonectria, Cylindrocladiella, Cylindrocarpon, and Campylocarpon; Phomopsis dieback was associated with Diaporthe; Esca was linked to Cadophora and Phaeoacremonium; and Eutypa dieback was associated with Paraeutypella. Newly reported fungal genera were found in 15 of the 17 provinces, with the exceptions of Shandong and Gansu. Botryosphaeria dieback was the most commonly occurred GTDs in China (35.5% ), followed by Black foot disease (23.2% ), Phomopsis dieback (13% ), and Esca (2.8% ). Furthermore, the study observed instances of co-infection involving two or more grapevine trunk diseases. Co-infections frequently involved combinations of Botryosphaeria dieback with Black foot disease or Phomopsis dieback. Disease occurrence was also closely correlated with vine age, with older vines of the same cultivar showing more severe symptoms.【Conclusion】All five major GTDs are now present in China, and each of the 17 surveyed provinces/municipalities reported occurrences of GTDs. The geographic range of GTDs has expanded, and the complexity of disease composition has increased, posing greater challenges for control. This study clarifies the main symptoms, types, and distribution of GTDs in China, providing important data to support grape production, viticulture practices, and the development of effective disease management strategies.