Physiological Changes Due to Drought Stress in lines derived from interspecific hybridization of safflower

Wild relatives of safflower have high potential of  hybridization with cultivated safflower and have a high tolerance to biotic and abiotic stresses, especially drought stress. This study was conducted to investigate the effect of drought stress on the physiological traits and their relationship with seed yield in F4 lines drived from interspecific hybridization of safflower. For this purpose, 12, 13 and 14 lines derived from three crosses of Carthamus tinctorius × Carthamus palaestinus (TP), Carthamus tinctorius × Carthamus oxyacanthus (TO) and Carthamus palaestinus × Carthamus oxyacanthus (PO) with 3 parental species (total 45 lines) were evaluated separatly under both normal irrigation and drought conditions. In the first study, F4 lines were evaluated for understanding the physiological mechanisms of drought tolerance, and in the second study, the effect of selection for seed yield in F3 on these traits in F4 was investigated. The results of the first study showed that TP crosses had higher seed yield than the other two crosses under normal irrigation condition, but there was no significant difference among the crosses under drought stress condition. The parental species showed significant differences for relative leaf water content, proline content, malondialdehyde, chlorophyll a and chlorophyll fluorescence. However, interspecific populations showed no significant differences for most of these traits under drought stress condition. These results may indicate the transfer of resistance genes from wild species to the cultivated safflower. The results of the second study showed that TP, PO and TO populations were different in terms of physiological traits, and it was revealed that selection efficiency was depend on the type of studied population. Selection in the TP population, which was derived from crossing between the cultivated species and wild species  of C. palaestinus, showed higher efficiency due to selection than the TO and PO populations in which  C. oxyacanthus was one of their parents.Therefore, with considering the physiological traits and seed yield, TP population was recognized as the best population for breeding programs.