To confirm the phenotypes observed under NY field conditions were due to D. ampelina alone, the following experiment was performed: Two-bud green cuttings were taken from green shoots of California greenhouse stock plants in October 2015, December 2015 and February 2016, corresponding to three independent, replicated experiments. Cuttings were rooted in perlite in the greenhouse [natural sunlight photoperiod, 25 ± 1 °C (day), 18 ± 3 °C (night)] with intermittent water mist (5 s every 2 min during daylight). Roots formed after 2 weeks, at which point cuttings were transplanted into a potting mix of peat, sand and perlite (1:1:1, v/v/v) in plastic trays (58 × 40 × 22.5 cm; XL High Dome Propagator, Garland Products, England). For each of the three experiments, a total of 24 inoculated plants per genotype [parental vines V. cinerea B9 and ‘Chardonnay’, four resistant progenies (454064, 455035, 454053, 454058) and six susceptible progenies (454066, 454071, 455072, 455082, 454045, 454077)] were evenly divided among four trays (six plants per genotype per tray), with replicate plants planted in a row. A separated tray with six plants per genotype was prepared for non-inoculated control. After 4 weeks, at least five leaves were present on each plant and the youngest internode was tagged.