Reaction of Vitis genotypes at the National Active Germplasm Site to downy mildew infection under tropical humid conditions of India

Two hundred and sixty six grape accessions at National Centre for Grapes, Pune were evaluated for their resistance/susceptibility to downy mildew during three consecutive natural epiphytotic conditions from 2004 to 2006, using the IPGRI/UPOV/OIV rating scale of 1–9. Twelve accessions, viz. Maroo Seedless, Bianca, Sirius, Madhu Angoor, Khalili, Seyve-Villard 12–375, Seyve-Villard 23–501, EC 38478, Carolina Black Rose, Seyve-Villard 18–315, Seyve-Villard 12–309 and Seyve-Villard 18–402 were rated as highly resistant. Seven accessions, viz. Seibel 9813, Seibel 9308, Seyve-Villard 12–364, Champanel, Amber Queen, 1613 C, Sauvis IP 365 were rated as resistant. The field reaction of these accessions was confirmed in vitro by leaf disc technique. Accessions H-533 and Concord (V. labrusca) were rated as moderately susceptible. All other accessions, including most of the commercial cultivars were found susceptible to highly susceptible to downy mildew.