Evaluation of Resistance of Bread Wheat Cultivars to Russian Wheat Aphid at Seedling and Stem Elongation Growth Stages

Twenty-two bread wheat cultivars along with susceptible (Sholeh) and resistant (Azadi) control cultivars were evaluated for resistance to Russian wheat aphid of two growth stages including seedling and stem elongation in greenhouse. Five adult aphids per plant were used for infestation. Leaf chlorosis at seedling and stem elongation stages and leaf rolling at seedling stage were measured. Other morphological and agromic traits were also measured at the end of the experiment. Rasol, Mahdavi and Arvand were identified as resistant, and Karoun as susceptible cultivars at seedling stage. There was no significant correlation between leaf rolling and chlorosis at seedling stage. In stem elongation stage, Azadi, Tabasi, Bayat and Kavir were highly resistant and Sholeh, Karoun, Rasoul and Karoun were highly susceptible cultivars. At stem elongation stage, leaf chlorosis did not have significant correlation with other traits. At seedling stage, grain numbers per spike and pedincle length decreased significantly(21% and 23%, respectively) by infestation of aphid. At stem elongation stage, however, pedincle length and dry weight decreased significantly(20% and 17%, respectively). All cultivars were more susceptible at seedling than stem elongation stage.