Three related full sib, F1 families were derived from the cross of four parental genotypes: V. vinifera ‘Chardonnay’ clone 95, V. cinerea B9, Illinois 547-1 (V. rupestris B38 × V. cinerea B9) and the complex hybrid ‘Horizon’ (‘Seyval’ × ‘Schuyler’, whose pedigree includes V. vinifera, V. labrusca, V. aestivalis and V. rupestris (Reisch et al. 1982). The ‘Horizon’ × Illinois 547-1 family (366 vines) resulted from crosses made in 1988 (Dalbó et al. 2000) and 1996. Families ‘Horizon’ × V. cinerea B9 (162 vines) and ‘Chardonnay’ × V. cinerea B9 (148 vines) resulted from crosses made in 2009. For all families, in the year following cross-hybridization, seeds were stratified prior to germination, and seedlings were grown in an irrigated field nursery. Two years after cross-hybridization, vines were transplanted to a permanent vineyard in Geneva, New York. Single vines per genotype were planted 1.2 m apart. A control block was included in each row, with the following genotypes: V. vinifera ‘Chardonnay’ (susceptible to powdery and downy mildew), V. hybrid ‘Chancellor’ (Seibel 5163 × Seibel 880) (susceptible to powdery and downy mildew), V. rupestris B38 (resistant to powdery and downy mildew, V. hybrid ‘Horizon’ (‘Seyval’ × ‘Schuyler’) (intermediate resistance to powdery and downy mildew) and the breeding selection NY88.0514.04 (resistant to powdery and downy mildew). Powdery mildew-susceptible control ‘Chardonnay’ was planted after every 15 seedling vines. Parental lines V. cinerea B9 and Ill. 547-1 are also classified as resistant to powdery and downy mildew.