Cylindrocarpon species associated with black-foot of grapevine in Northeastern United States and Southeastern Canada.
Black-foot disease of grapevine is caused by a complex of soilborne fungi. The most common and virulent species, which are found across all major grapegrowing regions of the world, are Cylindrocarpon liriodendri (C. liriodendri) and C. macrodidymum (teleomorph=Neonectria). Other species with a more limited distribution and uncertainty regarding their pathogenicity include C. destructans, C. obtusisporum, C. pauciseptatum, Campylocarpon fasciculare (C. fasciculare), and C. pseudofasciculare. The goal was to identify the species associated with black-foot disease in vineyards of the northeastern United States (U.S.) and southeastern Canada as such regions have not previously been surveyed. Recent expansion of winegrape acreage in these regions necessitates a clear understanding of the disease risks. Eleven U.S. states and two Canadian provinces were surveyed. Genus-level identification was based preliminarily on colony morphology. Species-level identity was based on phylogenetic analysis of two nuclear loci, 5.8S rDNA and β-tubulin, using voucher specimens and sequences with high sequence identity. We report for the first time from Canada recovery of C. liriodendri, C. macrodidymum, and C. destructans from symptomatic grapevines. Also reported are species not previously identified from black-foot symptomatic grapes anywhere in the world, including C. didymum and a Neonectria mammoidea-like species. Results suggest that local viticultural practices, primarily burying the vine underground during winter, may create injuries, and thus exacerbate infection by wound pathogens such as Cylindrocarpon. Overall this work improves the knowledge of black-foot disease in these nascent grapegrowing regions and will be helpful to growers in their decisions regarding viticultural practices, planting, and disease management.