Yeld performance and grain lipid composition of standard and oleic sunflower as affected by water supply

Sunflower has potential in Mediterranean farming systems because of the modest auxiliary input requirement, appreciable productivity and quality of raw material. These aspects are affected by the interactions among genetic, environmental and agronomic factors, which have not been fully explored. Therefore, the effects of four water regimes as proportion of crop evapotranspiration (0%, 33%, 67%, 100%) on grain yield and its components, oil yield and grain lipid constituents, i.e. fatty acids (FAs), unsaponifiable matter (UM), phytosterol (Phy), policosanol (PC) and tocopherol (Toc) fractions of a standard and an oleic sunflower hybrids were assessed in a 2-year field experiment. The relationships between crop productive traits and oil quality features were also analysed. In general, as the water supply (WS) increased grain yield and related traits as well as achene’s lipid synthesis and oil yield of each genotype (G) were positively affected. Conversely, the significant WS×G interaction found for the grain lipid composition indicated that the hybrids responded to different water treatments by modifying the proportions of major FAs as well as the UM and its total Phy, PC and Toc concentrations, with non-univocal percentage changes of their respective compounds. An increase of the unsaturation ratio of oil occurred when water (rainfall + irrigation) input increased, although at different level for each hybrid according to their genetic constitution. Because of the influence of warm climatic conditions, standard hybrid provided oil with an oleic–linoleic acid balance similar to that of mid-oleic typology. Within the oil UM, which contains also bioactive metabolites involved in the resistance of the plant to various abiotic constrains, total Phy concentration increased and total PC concentration decreased as the water (rainfall + irrigation) input was reduced, but to a different extent in the two hybrids. The most effective combinations of studied treatments for total Toc concentration were standard hybrid irrigated at both 33% and 67% of ETc replacement and oleic hybrid without irrigation. The results suggest that growing sunflower in a water-limited Mediterranean-type environment is possible to produce satisfactory grain and oil yields with an appropriate use of irrigation. Some oil quality characteristics suitable for different industrial uses could also be achieved by a combination of WS with standard or oleic typology of sunflower hybrids.