The response of yield and fatty acids composition in late planting of safflower genotypes to ascorbic acid and jasmonic acid application under deficit irrigation regimes

Drought stress is a major environmental constraint which inhibits the growth of plants and limits crop production. Nowadays, the application of antioxidants and plant growth regulators has discussed for decreasing the negative effect of different stresses. Ascorbic acid and jasmonic acid have substance caused witch the resistance to biotic and abiotic stresses. Ascorbate is a major metabolite in plants. It is an antioxidant, in association with other components of the antioxidant system, protects plants against oxidative damage resulting from aerobic metabolism and photosynthesis. Jasmonic acid (JA) is a plant-signaling molecule that shows a wide range of plant responses, with effects at the morphological to molecular levels. Many morphological, physiological, and biochemical processes occurring within the plants can be regulated by JA Previous studies have documented that foliar application of JA and Ascorbic acid could modulate plant physiological responses towards abiotic stress tolerance. Considering the importance of safflower plant in terms of quantity and quality of oil, it seems that increasing the yield per unit area under low irrigation conditions is a suitable way to increase the production of this plant so the aim of this study is evaluation of the effect of foliar application of jasmonic acid and ascorbic acid on grain yield, yield components, oil percentage and fatty acids composition of safflower genotypes under deficit irrigation regimes.

The experiment was set out in a split plot factorial in a completely randomized block design with three replications at Shahrekord University Agricultural Research Station during spring planting season 2017. The main factor as deficit irrigation consisted of three levels of irrigation of 100%, 75% and 50% of the plant's water requirement of safflower and sub-factor including safflower genotypes including Sinai, Isfahan local and Faraman and foliar application with three levels including (control, foliar application of jasmonic acid with 0/5 mM concentration and foliar application of ascorbic acid with 20 mM concentration.

Results indicated that deficit irrigation tratments caused a significant reduction in height plant, head number per plant, number of seed per head, seed thousand weight, seed yield, oil percentage, unsaturated fatty acids contains linoleic acid and oleic acid. The lowest values of seed yield (1382kg.ha-1) and oil percentage (26/67) were obtained in treatment of 50 %plant water requirement and the highest seed yield (1635 kg.ha-1) and oil percentage (27.21kg.ha-1) were aachived in 100 % plant water requirement. There was a significant difference between safflower genotypes, so the highest seed yield (1676 kg.ha-1) and oil percentage (27.82) were obtained in Sina genotype and the lowest seed yield (1341kg.ha-1) and oil percentage (27.66) were belonged to Local Isfahan genotype. The interaction of deficit irrigation tratment × genotypes were significant on height plant, the unsaturated oleic acid content and the saturated fatty acid content palmitic acid so that the highest of height plant (91.99 cm) and oleic acid content (15.5 percentage) was recorded in 100% of the plant's water requirement conditions and sina genotyp but the highest content of palmitic acid (10.37percentage) was recorded in 50% of the plant's water requirement conditions and sina genotype. Jasmonic acid and ascorbic acid treatment increased the grain yield, yield components, oleic acid and linoleic acid content and reduced the palmitic acid and stearic

The results showed that significant difference between genotypes and foliar applicaton treatments, such as the content of unsaturated fatty acids, can be used for the selection of superior genotypes for economic production and commercial cultivation and reduce the adverse effects of deficit  irrigation stress in the field conditions.