The effect of water stress during grain filling on the yield and processing quality of sunflower seed

The oil and protein contents of sunflower seed are affected by water stress. Hullability is a seed quality trait which affects the efficiency of oil extrusion and the quality of the oil cake produced from the seed. Apart from cultivars, hullability is also affected by environmental conditions during seed filling. The effect of water stress, the major environmental factor for yield, on hullability is, however, unclear. The influence of an irrigated and a dryland treatment during the grain filling stage on seed composition, some physical seed properties including hullability, the potential oil and oil cake yield and the protein content of the oil cake of three cultivars was compared in a field trial. The relative water content of the leaves showed that the dryland treatment induced a mild to moderate stress compared to the irrigated treatment, which persisted for 25 days from the opening of the inflorescences. Seed yield was reduced by 23%, hullability by 14% and kernel oil content by 2.3% owing to this water stress. Seed yield did not differ amongst cultivars but all physical seed properties differed. The potential oil yield, oil cake yield and composition of the oil cake, however, were not affected by the water stress. Owing to the difference in seed composition and hullability, the potential oil yield, oil cake yield and protein content of the oil cake differed between cultivars.