CHANGES IN THE FATTY ACIDS COMPOSITION OF SEED OIL IN DIFFERENT CULTIVARS OF SESAME UNDER FOLIAR APPLICATION OF SULFUR
Sulfur plays an important role in the determination of seed yield (SY) and quality of oilseed crops. However, the effect of foliar application of sulfur is not yet known on SY and oil yield (OY) of sesame genotypes. Therefore, a field factorial experiment based on a randomized complete block design was conducted during two years of 2017 and 2018. Effects of foliar application of sulfur at five concentrations, namely S1, S2, S3, S4, and S5 indicating 0, 1, 2, 4, and 8 mg/L were investigated on endemic and non-endemic sesame cultivars, including C1 (Darab 1), C2 (local Fasa), C3 (Iraqi), C4 (Takpar Dashtestan), and C5 (Sheshpar Borazjan). Treatments with foliar application of sulfur at concentrations of 6 and 8 mg/L were statistically superior to other treatments in terms of SY and OY with no statistically significant differences. The highest SY belonged to C1, C4, and C5, and the highest OY was recorded in C4. Interaction of C5 and C4 with foliar application of sulfur at 8 mg/L led to the highest SY and OY, respectively, among the experimental treatments. There was a significant positive correlation (r = 0.85**) between SY and OY. A total of 11 fatty acids, including four saturated fatty acids (SFAs: myristic, palmitic, margaric, and stearic acids) and seven unsaturated fatty acids (UFAs: palmitoleic, ginkgolic, oleic, linoleic, α-linoleic, arachidonic, and gadoleic acids) were isolated from the tested sesame cultivars. The results indicated different behaviors of genotypes in terms of fatty acid content. Oleic acid (44.5%) and linoleic acid (36.8%) were the most UFAs in the sesame cultivars. With increasing sulfur levels, all fatty acids, except linoleic acid, increased in sesame seeds. Among the studied fatty acids, the highest rate of increase belonged to arachidonic acid, which increased by 17.2% with rising concentrations of sulfur spraying compared to the control without foliar application. SY and OY had a significant positive relationship with linoleic acid (r = −0.79) at a probability level of 5%. There were significant negative correlations between SY and oleic and stearic acids (r = −0.75 and r = −0.85, respectively) at a probability level of 5%.