In the field, lesions on dormant canes varied from absent (asymptomatic) to widespread with black, corky wood and canes that were visibly stunted (Fig. 1a). All parental genotypes showed few to no symptoms, having either a score of 0 (for one vine of ‘Chardonnay’, one vine of V. cinerea B9 and two vines of ‘Horizon’), or a score of 1 (three vines of ‘Chardonnay’, seven vines of V. cinerea B9, six vines of ‘Horizon’ and four vines of Illinois 547-1 displaying a small number of discrete cane lesions). While no parental plants showed scores of 2 or 3, these extremely susceptible phenotypes were observed for a proportion of progeny in all three F1 families (Fig. 2).Fig. 2Segregation of dormant cane symptoms and cluster symptoms in three F1 families. a ‘Chardonnay’ × V. cinerea B9, b ‘Horizon’ × V. cinerea B9 and c ‘Horizon’ × Illinois 547-1. Disease severity on canes was measured for 2 years 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. On clusters, symptoms such as black superficial spots, shriveled berries and dry rachis were scored as present (1) or absent (0). Across all years, average cane severity was 0.75, 0.88, 0.75 and 1 for ‘Chardonnay’, V. cinerea B9, ‘Horizon’ and Illinois 547-1, respectively and 0 for the cluster-bearing parents ‘Chardonnay’ and ‘Horizon’