Development of a molecular diagnostic to discriminate between Fomitiporia species and advancements in detection of the main grapevine decline-related pathogens in propagating material and mature vines

A comprehensive study was conducted on the prevalence of grapevine trunk diseases in Greece, focusing specifically on contamination of grapevine propagation material by Phaeomoniella chlamydospora and black foot disease-related species. Additionally, detection of esca pathogen Fomitiporia mediterranea, causing white rot in grapevine and other woody hosts, was assessed using a new PCR-based assay that distinguishes F. mediterranea from F. punctata. Development of a nested PCR assay, combined with a cost-effective DNA extraction protocol, revealed a high percentage of infection by P. chlamydospora (51%) and Ilyonectria species associated with black foot disease (28%) in different types of grapevine propagation material (dormant cuttings, field-rooted benchgrafts and green-growing plants). Interestingly, black foot disease-related pathogens were more prevalent in nursery plants grown in the field for 6 months (57%) than in other types of propagation material and compared with P. chlamydospora (43%), indicating increased infection of propagation material during growth in the nursery field. The cost-effective molecular method developed in this study could be used in mass inspections of propagation material for phytosanitary purposes. Finally, using primers specific for F. mediterranea and F. puncata developed in this study, combined with the universal ITS4 primer, a collection of Fomitiporia isolates from mature grapevine and other woody hosts from Greece and Italy (southern Europe) were characterized as F. mediterranea, whereas German and Swedish isolates from forest plants (central Europe) were classified as F. punctata. The developed primers can discriminate between the two Fomitiporia species, which are indistinguishable based on culture and morphological characteristics alone.