First Report of Campylocarpon fasciculare Causing Black Foot Disease of Grapevine in Turkey

Variation in Fungal Community in Grapevine (Vitis vinifera) Nursery Stock Depends on Nursery, Variety and Rootstock

Grapevine trunk diseases (GTDs) are caused by cryptic complexes of fungal pathogens and have become a growing problem for new grapevine (Vitis vinifera) plantations. We studied the role of the nursery, variety, and rootstock in the composition of the fungal communities in root collars and graft unions of planting material in Catalonia (NE Spain). We compared necrosis and fungal communities in graft unions and root collars at harvest, and then after three months of cold storage. We evaluated combinations of eleven red and five white varieties with four common rootstocks coming from six nurseries. Fungal communities were characterized by isolation and metabarcoding of the ITS2 region. Our data suggests that nursery followed by rootstock and variety had significant effects on necrosis and fungal community structure in graft and root tissues. Within the plant, we found large differences in terms fungal community distribution between graft and root tissues. Graft unions housed a significantly higher relative abundance of GTD-related Operational Taxonomic Units (OTUs) than root collars. More severe necrosis was correlated with a lower relative abundance of GTD-related OTUs based on isolation and metabarcoding analyses. Our results suggest that nurseries and therefore their plant production practices play a major role in determining the fungal and GTD-related fungal community in grapevine plants sold for planting. GTD variation across rootstocks and varieties could be explored as a venue for minimizing pathogen load in young plantations.

Taxonomy and multi-locus phylogeny of cylindrocarpon-like species associated with diseased roots of grapevine and other fruit and nut crops in California

Black foot disease is a common and destructive root disease of grapevine caused by a multitude of cylindrocarpon-like fungi in many viticultural areas of the world. This study identified 12 cylindrocarpon-like fungal species across five genera associated with black foot disease of grapevine and other diverse root diseases of fruit and nut crops in the Central Valley Region of California. Morphological observations paired with multi-locus sequence typing of four loci, internal transcribed spacer region of nuclear rDNA ITS1-5.8S-ITS2 (ITS), beta-tubulin (TUB2), translation elongation factor 1-alpha (TEF1), and histone (HIS), revealed 10 previously described species; Campylocarpon fasciculare, Dactylonectria alcacerensis, D. ecuadoriensis, D. macrodidyma, D. novozelandica, D. torresensis, D. valentina, Ilyonectria capensis, I. liriodendri, I. robusta, and two new species, Neonectria californica sp. nov., and Thelonectria aurea sp. nov. Phylogenetic analyses of the ITS+TUB2+TEF1 combined dataset, a commonly employed dataset used to identify filamentous ascomycete fungi, was unable to assign some species, with significant support, in the genus Dactylonectria, while all other species in other genera were confidently identified. The HIS marker was essential either singly or in conjunction with the aforementioned genes for accurate identification of most Dactylonectria species. Results from isolations of diseased plant tissues revealed potential new host associations for almost all fungi recovered in this study. This work is the basis for future studies on the epidemiology and biology of these important and destructive plant pathogens.