Evaluation of physiological indices of induced changes in safflower cultivars under biotic stress

Plants have a variety of defense mechanisms, which are often induced after herbivores attacks. Induced defense mechanism has advantages for plants by reducing the performance or preference of herbivores toward host plants such as aphids, which later attack the plant. In current research, in first stage, four safflower cultivars including, Sofeh, Goldasht, Faraman, Mahali-Isfahan and a wild safflower species, Carthamus oxyacantha, were exanimate feeding of Helicoverpa armigera (Lep.: Noctuidae) larvae. Then all larvae were removed and these plants were maintained uninfected for 72 h. In second stage, four unwinged adult of safflower aphid, Uroleucon carthami (Hem.: Aphididae) were placed on both infested and control plants. Then they were reared for 15 days. The results showed that cotton bollworm larval feeding on safflower, as an induced resistance element, had a significant on plant physiological indices and aphid reproduction. Indicators such as H2O2, prolin, protein content and reducing sugars were significantly affected by the biotic stress of the larva compared to the control. These changes indicate that the responses of different safflower varieties to larvae was not the same and cultivars like Mahali-Isfahan showed better compatibility for induced resistance and accumulation of important metabolites such as oxygenated water, prolin, sugar and protein.