Evaluation of relative resistance to English grain aphid(Sitobion avenae (F.)) in dryland wheat commercial varieties and developted lines in cold conditions

Investigation was made on relative resistance of 10 bread wheat cultivars to English grain aphid (Sitobion avenae (F.)). The study was conducted in a completely randomized blockes design with 10 treatments each with 20 replicates for bread wheats. The survival rate of the nymphs¡ their developmental time¡ adult fecondity and the relevant rate of natural population increase (rm value) within the first 15 days of reproductive period¡ at three tillering¡ stem elongation and heading growth stages of the plants was calculated. ANOVA of the results based on factorial experiment (10×3) with two factors¡ variety and growth stages¡ indicated highly significant differences (P