DIFFERENTIAL PHYSIOLOGICAL RESPONSES OF THREE SESAME GENOTYPES TO DROUGHT STRESS AND THE EXPRESSION OF ANTIOXIDANT GENESHiba Fouad Abdulfatah, Dhia S. Hassawi and Saeid Abu-RommanAbstract This study was conducted to determine the physiological responses and the expression of major antioxidant genes (Cu/Zn-SOD, CAT, and APX) to drought stress in three sesame (Sesamum indicum L.) genotypes. Drought conditions were imposed at three levels: D1 (100%), D2 (50%), and D3 (25%) of field capacity on three major Iraqi genotypes of sesame, namely Wadaa, Sumer, and Local. The physiological results indicated that variety Wadaa was characterized by the highest relative water content (82%). The expression of Cu/Zn- SOD gene was influenced by drought in Wadaa variety and recorded the lowest gene expression compared to non-stress plants at 50% of field capacity. Gradual increase of expression was recorded in Sumer and Local varieties to reach 43.63 and 50.98-fold over, respectively of the normal expression. The expression of CAT gene was up-regulated in both Wadaa and Sumer for treatments D2 and D3, and up-expression for treatment D2 with the Local variety while down-regulated from normalized expression for D3 treatment (1.56-fold). The expression levels of APX gene increased in Wadaa variety for the treatment D2 and decreased for the treatment D3 by 83.33-fold. While its expression up-regulated for the treatments D2 and D3 in Sumer variety as well as in treatment D2 in the Local variety. Severe drought at 25% of field capacity caused down-regulated in APX in Local variety and scored 1.26-fold than non-stress plants. |