physiological and Biochemical responses of different sesame (sesamum indicum) genotypes under salinity stress

Sesame seeds are a good source for food and health due to their protein and unsaturated fatty acids and secondary metabolites such as lignans. Soil and water salinity is one of the most important factors limiting the growth of this crop. By examining the physiological reactions related to salinity tolerance among different landraces and cultivars, tolerant and sensitive cultivars can be selected and used in breeding programs and cultivation development of this important oilseed. For this purpose, physiological reactions in eight different sesame genotypes in a factorial experiment based on a completely randomized design with the main salinity factor due to mixing Caspian Sea water with normal water at 3 levels(control, 6 & 9 dSm-1) and sub-factor 8 Sesame genotype includes Babol, Dashtestan 2, Oltan, Pakistani, tn-78-389 and tn-78-393, Halil, Naz single-branched genotypes in three replications in pots in the greenhouse of the Plant Breeding Department of Sari University of Agricultural Sciences and Natural Resources in the year 2020 were examined. The results of this experiment showed that at salinity levels of 6 and 9 dS, among the eight different genotypes of sesame studied, Oltan cultivar with the highest amount of total dry weight (8.42 & 5.27 gr), proline (10.35&15 μmol/g fresh leaf weight), membrane stability index ( 82.65&74.14%), relative water content(81.33 & 69.33%), leaf chlorophyll and carotenoid content(based on mg/g fresh weight), chlorophyll a(0.74&0.7),total chlorophyll(1.12&0.95)and carotenoids(0.41&0.46)and antioxidant enzymes activities (based on enzyme unit per gram fresh weight), superoxide dismutase(18.22&29.05), ascorbate peroxidase(14.9&19.21),catalase(1.51), guaiacol peroxidase(4.8&5.43),potassium(6.6%),sodium to potassium ratio index (0.06&0.12) and the lowest amount of sodium(0.41&0.7)was more tolerant of stress than other cultivars. In contrast, Pakistani cultivar with the lowest amount of total dry weight (5.12 & 2.14 gr), proline(5.86&6.7 μmol/g fresh leaf weight), membrane stability index(66.31 & 57.86%), relative water content (58&48.33%), leaf chlorophyll and carotenoid content (based on mg / g fresh weight), chlorophyll a(0.46&0.37), total chlorophyll(0.69&0.5)and carotenoids(0.25&0.27)and Antioxidant enzymes activities (based on unit of enzyme per gram of fresh weight), superoxide dismutase (11.61&10.31), ascorbate-peroxidase (8.61&8.78),catalase(0.84),guaiacol peroxidase(1.77&2.16), potassium(3.68%), sodium to potassium ratio index(0.59&1.12)and the highest amount of sodium(2.15&2.57)was the most sensitive cultivar in stress tolerance compared to other cultivars. Based on the evaluated traits and the response of the studied cultivars to salinity stress, oltan was identified as a tolerant cultivar and Pakistani as a salinity sensitive cultivar compared to the other cultivars. Therefore, these cultivars can be suggested for use in future breeding programs to introduce new cultivars.