Influence of salt stress on seed yield and oil quality of two sunflower hybrids

Sunflower is a major oil seed crop worldwide, and it is also an important crop in Mediterranean areas where salinity is an increasing problem. In this paper, the effect of saline irrigation water on seed yield and quality of sunflower was evaluated. A pot experiment was carried out over two crop seasons on two hybrids - a standard one (Carlos) and a high oleic one (Tenor) - submitted to five salinity levels of irrigation water (0.6, 3, 6, 9 and 12 dS m(-1)). Soil salinity was monitored over the entire crop cycle, and leaf ion content was determined at maturity. Tenor showed higher Na+ and Mg2+ content but lower K+ values. No difference between the two hybrids was observed for Cl- content. A progressive increase in leaf Na+, K+ and Cl- contents and Na+/K+ ratio with increasing salinity level was observed. Seed weight per head, 1000 achene weight, number of seeds per plant and oil yield significantly decreased under salt stress in both hybrids. The percent seed yield decrease was higher per unit increase in electrical conductivity of irrigation water, ECw (8%), than per unit increase in electrical conductivity of saturated-soil extracts, ECe (5%). Concerning oil fatty acid composition, the main significant difference as result of salt stress was a progressive increase in oleic acid content, from 82.2% to 86.7% for Tenor and from 21.8% to 27.3% for Carlos, which was consistent with a decrease in linoleic acid content, from 5.9% to 3% for Tenor and from 66% to 61.3% for Carlos. These results confirm the possible inhibition of oleate desaturase under salt stress.