The effect of priming on physiological and yield characteristics of different sesame varieties under drought stress

Sesame is an important oilseed in which contains rich source of oil, protein, phosphorus and calcium. Drought is considered as the most obvious environmental factors in reducing the growth and yield of sesame in arid and semi-arid areas. Due to high economic importance of sesame from one hand, and high efficiency of priming and its cheapness to alleviate adverse effect of drought stress from other hand, the aim of present study was to evaluate drought stress and various priming methods on yield component and physiological features of three different sesames.

The study was conducted for two years in spilt plot factorial design with three replications in the farm of research center of Bushehr city. The main factor consisted drought stress in three levels of drought stress included irrigation after drainage of 45% FC (control or without stress), irrigation after drainage of 65% FC (mild stress) and irrigation after drainage of 85% FC (severe stress), five priming treatments included control (without priming), hydropriming, zinc sulphate, potassium sulphate and salicylic acid (SA) in three sesame verities (Oltan, Dararb 14, Karaj) were evaluated. Various yield and physiologic parameters such as chlorophyll content, soluble sugar and some antioxidant enzymes activities were investigated.

According to the results, with increasing stress level, 1000 seed weight, harvest index, seed yield, capsule number, total chlorophyll, leaf area index, relative water content have shown decreasing while proline and soluble sugar have increased. Furthermore, it was found that priming had a significant impact on yield and physiological traits. The highest yield, harvest index and 1000 seed weight were respectively found in priming with SA 1153, 25.7 and 2.66 kilogram per hectare while the least were respectively reported in control treatment (without priming) 968, 23.8 and 2.51. Also Karaj and Oltan, respectively have shown the highest and the least seed yield 1269 and 889 kilogram per hectare. The highest proline content (1.29 mg/g FW) in Karaj variety and the lowest amount (1.17 mg/g FW) in Oltan veriety were shown. However, the highest soluble content (1.03 mg/g FW) in Oltan genotype and the least one (0.97 mg/g FW) in Karaj were reported. Also, the highest and lowest amount of relative water content and total chlorophyll were in Karaj and Oltan verities, respectively. Moreover, the investigated cultivars had shown different responses in physiological traits. In most yield traits, cultivar Karaj and Oltan showed the highest and least yield features.

Drought stress caused less sesame yield, but different genotypes reaction to stress were not the same. Although, desirable effects of seed priming with Salicylic acid, ZnSO4 and K2SO4, that by maintaining chlorophyll content and finally aid to photosynthesis process, was remarkable. In present research, Karaj verity was more resistant to drought stress. According to SA and zinc roles on photosynthesis, osmolytes synthesis in alleviating adverse effects of drought stress and on the other hand, desirable effect of priming on sesame growth and yield, using SA, zinc sulphate and potassium sulphate for increasing yield in region facing with drought stress are recommended.