Seed yield and oil quality of sunflower, safflower, and sesame under different levels of irrigation water availability

Water deficit stress is a common environmental factor affecting growth and yield of crops, but comparative studies on quantitative and qualitative characteristics among oilseed crops do not exist in the literature. A three-year field experiment was conducted in a calcareous soil of East Azerbaijan, Iran to determine the impact of water deficit stress on a number of quantitative and qualitative characteristics of sunflower (Helianthus annuus L.), safflower (Carthamus tinctorius L.), and sesame (Sesamum indicum L). Four levels of irrigation, i.e., 40, 60, 80, and 100% of potential evapotranspiration (PET) were applied during the growing season. Low water availability significantly decreased seed yield in all oilseed crops, followed by a significant increase in malondialdehyde (MDA) and proline (Pro) content. Averaged over irrigation water availability levels, sunflower showed the greatest reduction in seed yield by 16.3%, followed by sesame (12.8%) and safflower (9.4%). The seed yield reduction in all crops was mainly due to a reduction in seed weight and a reduction in seed number in capitula or capsules. Averaged over irrigation water availability levels, sunflower showed the greatest reduction in oil yield by 22.5%, followed by sesame (13.3%) and safflower (10.2%). Mild lack of irrigation water availability (80% of PET) neither affected negatively nor improved oil percentage, particularly in safflower and sesame. Severe lack of irrigation water availability (40% of PET) significantly reduced oil percentage, particularly in sunflower. A significant reduction in oleic acid (OA), linoleic add (LA), linolenic acid (LNA), and palmitic acid (PA) content due to low availability of irrigation water was observed in all crops. Apart from breeding efforts for improving crop resistance to drought, management practices should be considered to reduce drought-related issues in major oilseed crops.