Evaluation of Drought Stress Indices of TwoVarieties Sesame of Local Behbahan and Shevin

Background and objectives: Drought stress is the most important environmental factor limiting the growth and development of plants around the world, as growth retardation due to drought stress is reported more than other environmental stresses. Sesame due to its resistance to drought and heat is of great importance in the development of agriculture in arid and semi arid regions during summer planting. The purpose of this research was to investigate the effect of drought stress by applying different levels of T-Tape drip irrigation and identification of superior cultivar based on stress indices.

Materials and methods: In order to study and evaluate drought stress indices in drip irrigation method, yield, grain yield components, oil yield, seed oil percentage and grain water use efficiency were tested in 2018-2019 in Behbahan Agricultural Research Station. The experiment was conducted as split plots in randomized complete block design with 3 replications. The main factor included water leveles in drip irrigation at four levels of 40, 60, 80 and 100% of water requirement from the beginning of flowering stage and the sub factor including Varieties in two levels including local of Behbahan and Shevin. For comparing the results of the measured and calculated results, Pearson correlation coefficients were used for all measured or calculated parameters.

Results: Comparison of the average water use efficiency of irrigation and cultivar interactions showed that 100% water requirement and local of Behbahan cultivar with water use efficiency of 0.222 kg/m3 of sesame seeds were superior treatments. Average water consumption in one year of experiment was 40, 60, 80, 100% water requirement and control treatment (Surface irrigation) respectively 35.0, 41.4, 47.8, 54.2 and 65.1 cm water. The results of Pearson correlation coefficient showed the highest correlation of 1000 grain weight with 0.9305 with grain yield index, which indicates the effective role of 1000 seed weight gain in increasing grain yield.Due to the higher values of SSI and TOL indices in Behbahan's local variety compared to Shevin, and also the low rates of STI, MP, GMP, HM, YI and YSI indices in Behbahan's local cultivar, compared with Shevin , can be Behbahan's local cultivar for drought stress It was introduced as a superior treatment.

Conclusions: Increasing plant height significantly correlated with increasing the number of seeds per capsule. The most significant correlation between number of seeds per capsule as one of the important components of yield with plant height and plant height with consumed water volume, shows the important role of optimum management of deficit irrigation in sesame crop. The yield under tension of local Behbahan sesame variety was closer to Shevin cultivar than non-stressed yield and this factor was effective in increasing the TOL index in local Behbahan sesame variety relative to Shevin. Variety of Sesame is resistant to drought stress, and the correlation coefficient of its TOL index is more negative. The identical trend of changes in the MP index led to the introduction of this index of the most insensitive stress index and the TOL index as the most resilient indicator for stress variations. The TOL index divides the two varieties sesame according to their performance variations. The lower the variation, the variety Sesame will show more stability under stress conditions.