Screening of Rapeseed-Mustard Genotypes for Resistance to Mustard Aphid Infestation

Rapeseed-mustard, a key oilseed crop in India, faces significant yield losses due to insect pests, particularly the mustard aphid (Lipaphis erysimi). This study evaluated the resistance of 79 rapeseed-mustard genotypes to aphid infestation across three growth stages (aphid appearance, full flowering, and full siliqua formation) during the 2022-23 Rabi season. Results revealed significant variability in aphid resistance among genotypes and across growth stages. At the aphid appearance stage, 41 genotypes exhibited resistance (Aphid Resistance Index = 1), while 38 were moderately resistant. As the crop matured, aphid populations increased, and resistance levels declined. At the full flowering stage, 31 genotypes remained resistant, with 46 moderately resistant. At the full siliqua formation stage, only six genotypes were resistant, with 69 moderately resistant and four tolerant. No genotypes were categorized as susceptible or highly susceptible throughout the study, indicating a baseline level of resistance in the evaluated germplasm. Aphid populations ranged from 1.2 to 24.6 (aphid appearance), 3.2 to 59.0 (full flowering), and 2.6 to 173.4 (full siliqua formation) aphids per 10 cm twig. These findings emphasize the dynamic nature of host-aphid interactions and the crucial need for growth-stage-specific resistance evaluations in breeding programs. Identifying and utilizing resistant genotypes can significantly reduce reliance on chemical insecticides, promoting sustainable and eco-friendly aphid management strategies in rapeseed-mustard production.