Greeneria uvicola associated with dieback in vineyards of Sonora, Mexico

Abstract

The state of Sonora is the main grape production area in Mexico. Grapevine trunk diseases (GTD) are serious disease in this region. During the springs of 2017 and 2018, symptoms of yellow and wilted leaves, and necrotic buds, were observed in several vineyards in Sonora. Affected plants had numerous small, black and bright acervuli. This study aimed to identify the causative agent of this disease. Isolates were obtained from small pieces of damaged plant parts, and were cultured on potato dextrose agar. The developing mycelium was white but turned greyish white after 3 d. Multi-shaped black mucilaginous droplets appeared in the cultures after 2 d, and the agar in Petri dishes was completely covered with mycelium after 7 d, and the colonies had five or six rings with large numbers of conidiomata. Conidia were hyaline or light cream, fusiform, oval or ellipsoid, with truncated bases and narrow almost pointed apices, and were 6–10 mm long and 2–3 mm wide. Phylogenetically analysed concatenated sequences of the DNA from two representative isolates, from the internal transcribed spacer region, and large ribosomal subunit, showed they were in a separate clade which aligned with several strains of Greeneria uvicola, confirming the presumptive morphological identity of the isolates. This cosmopolitan ascomycete is responsible for bitter rot of grapes, but the role of this fungus as a cause of grapevine trunk diseases is little known. Pathogenicity tests of the isolates were performed on 1-year-old ‘Passion Fire’ grapevines plants, one of the new cultivars planted in Sonora. All of strains G. uvicola were pathogenic, and the fungus was recovered from the lesions, fulfilling Koch’s postulates. This is the first report on the pathogenicity of G. uvicola in wood tissues of Vitis vinifera in Mexico.

Keywords

• Diaporthales
• Melanconiellaceae
• multilocus typing
• grapevine trunk diseases