Field vines were subject to natural inoculation. Phomopsis symptoms were evaluated on dormant canes each autumn from 2011 through 2013 using the following disease severity scale: (0) no symptoms; (1) light infection, few discrete circular lesions; (2) moderate infection, widespread coalescing circular lesions; (3) severe infection, widespread coalescing misshapen lesions with blackened surface and corky texture (Fig. 1a). Symptoms on clusters were scored as present or absent before veraison in 2013 and 2014. As male vines did not set fruit, the number of samples was reduced to 65 observations in the ‘Horizon’ × V. cinerea B9 family and 58 observations in the ‘Chardonnay’ × V. cinerea B9 family. No cluster observations were made in the ‘Horizon’ × Illinois 547-1 family.Fig. 1Symptoms and Diaporthe ampelina isolation. a Phomopsis cane symptoms were scored on dormant canes using the following scale: (0) no Phomopsis symptoms observed; (1) light infection, small number of discrete lesions; (2) moderate infection, lesions coalescing, widespread; and (3) severe infection, lesions blackened, internode tissue corky and misshapen. b D. ampelina culture isolated from symptomatic canes (score 3), growing on potato dextrose agar. c Progression of symptoms on resistant (left) and susceptible (right) full siblings growing side by side in the vineyard on August 21 (upper) and September 10 (lower), 2013. d Phomopsis symptoms on green shoots and unripe berries