Screening of Cucumber Cultivars to Downy Mildew Caused by Pseudoperonospora cubensis in Natural Field Conditions

Downy mildew, caused by Pseudoperonospora cubensis, is a major limiting factor in cucumber production, particularly during the Kharif season under humid conditions. The present study was conducted to evaluate the field resistance of twelve cucumber cultivars against downy mildew during the Kharif 2023 season. Observations were recorded on the time of first disease appearance and percent disease index (PDI) at successive growth stages. The first appearance of disease ranged from 34 to 47 days after sowing (DAS), with Lalit-22 showing the earliest symptoms and Pant Khira-1 the latest. At 40 DAS, nine cultivars exhibited no visible symptoms, while Lalit-22, Honey, and Netra-007 recorded early infection with PDI values of 15.66%, 12.06%, and 14.33%, respectively. By 70 DAS, disease severity increased across all cultivars, with final PDI values ranging from 23.85% to 71.66%. Based on disease reactions, Ankur-07 and Gujarati Nirmala-2 were categorized as moderately resistant, while Lalit-22, Honey, and Netra-007 were found to be susceptible. The remaining cultivars were classified as moderately susceptible. The study highlights the importance of both delayed disease onset and reduced final disease severity as indicators of resistance. Cultivars showing moderate resistance, particularly Ankur-07 and Gujarati Nirmala-2, may serve as potential sources for resistance breeding programs aimed at enhancing downy mildew tolerance in cucumber.