Study of genetic diversity and evaluation of some sesame genotypes under salinity stress

Sesame is one of the oldest products known to man to date. Sesame was a valuable crop in the ancient world due to its drought resistance, ease of oil extraction from seeds and oil stability. Iran is one of the arid and semi-arid regions of the world in terms of climate. In these areas, low and scattered rainfall and high evaporation usually cause the accumulation of salts in the surface layer of the soil. Therefore, the salinity of soil and irrigation water causes significant morphological, physiological and chemical changes. Excess salt, that is, more than plants need limits crop growth and production and can lead to plant death.

In this experiment, 20 sesame genotypes were grown in greenhouses. The experiment was performed as a factorial in a completely randomized design with three replications. 75 mM sodium chloride was dissolved per liter of water and the pots were irrigated with saltwater. Percent morphological traits loss index (PML) was calculated.

According to the results of analysis of variance and comparison of the mean interaction of cultivar × stress in all studied traits were significant. American and Yellow- White cultivars with 17927 and 14.07 g, respectively, the highest and 714 and Dezful with 2.43 and 2.07 g, respectively, the lowest yield under normal conditions, and Oltan and American cultivars, respectively, with an average of 963 8.8 and 7.34 g had the highest and Darab 1 and Dezful had the lowest yield under stress conditions with 0.92 and 0.71 g, respectively. In this study, clustering method was used to group and separate useful (high yield) and susceptible (low yield) genotypes based on different traits. The results showed that the studied genotypes were grouped based on morphological traits and yield reduction percentage index using standard data. The studied genotypes were divided into 3 groups. In the first group, Oltan, American, Chinese, Dashtestan 2, 369 and 418 genotypes with the highest yield among the genotypes were studied. The second group included Darab 1, 730 and Dezful genotypes and the third group included other genotypes. In the first group, it is desirable to distinguish high-yield genotypes with desirable traits and the lowest percentage of yield reduction under salinity stress conditions from other genotypes.

The results of this experiment showed that there is a favorable variation among the study population, especially a significant difference was observed between the performance of genotypes in both normal environmental conditions and salinity stress. Correlation analysis of traits showed that under normal conditions, number of seeds per plant, number of capsules per plant and 100-seed weight, and under salinity stress, number of seeds per plant, number of capsules per plant and single plant weight had the highest correlation with yield. In this experiment, the best salinity tolerant lines were Oltan, American, Chinese, Dashtestan 2, 369 and 418 genotypes. It is noteworthy that these genotypes had a more stable performance than others in both conditions, so they have stress tolerance genes and can be considered in future studies. Also Darab 1, 730 and Dezful genotypes were the most sensitive genotypes to salinity stress in this experiment.