Epidemiology and Screening of Varieties Against Powdery Mildew of Okra Caused by Erysiphe Cichoracearum DC

Okra (Abelmoschus esculentus L. Moench) is an important vegetable crop widely cultivated in tropical and subtropical regions of the world. Its productivity is often constrained by several diseases, among which powdery mildew caused by Erysiphe cichoracearum is one of the most destructive fungal pathogens. The present investigation was conducted to study the epidemiology of powdery mildew and to evaluate nineteen okra genotypes under natural epiphytotic conditions for their reaction against the disease. The incidence of powdery mildew showed a negative correlation with rainfall, minimum temperature, evening relative humidity and evaporation, whereas morning relative humidity, sunshine hours and wind speed exhibited a positive influence on disease development. The developed regression model can be utilized for predicting powdery mildew severity under prevailing environmental conditions. The multiple regression equation obtained was: Y = 38.438 - 0.062X₁ - 10.945X₂ + 8.049X₃ + 3.765X₄ - 3.180X₅ = 4.590X₆ + 2.368X₇ + 1.266X₈, with a coefficient of determination (R² = 0.73), indicating a strong relationship between weather parameters and disease incidence. The field experiment was laid out in a Randomized Block Design and disease severity was recorded at regular intervals using a 0–5 disease rating scale. Based on percent disease severity, the genotypes were categorized into different reaction groups. Four genotypes, namely NBH-45, Karishma, Laxmi and Radhika, exhibited resistant reactions, while eight genotypes including Siddhi, Arka Abhay, VRO-8, Parbhani Bhendi, OH-940, PBNOK-6, PBNOK-4 and Parbhani Kranti were moderately resistant. Five genotypes showed moderately susceptible reactions, whereas Pusa Sawani and Pusa Makhamali were found susceptible. The identification of resistant and moderately resistant genotypes provides valuable genetic resources for breeding programs aimed at developing powdery mildew resistant okra varieties.