Effect of heat stress on seed yield components and oil composition in high- and mid-oleic sunflower hybrids
High temperature stress is a major environmental factor influencing processes such as growth, yield and quality of crops. The objective of this study was to assess the effect of heat stress, applied during grain-filling, on seed yield- and oil quality components in high- and mid-oleic sunflower hybrids. Genotypes were exposed to a temperature range of 24/36 °C (night/day) for 10 consecutive days starting at 15 days after flowering. Heat treatment altered all measured traits; however, genotypes differed in their sensitivity to temperature. Head diameter and the sterile area of the head increased, but number of filled seeds per head and seed weight were reduced. HO 4 showed an increase in grain yield, but showed the largest decrease in oil content. The average oil concentration was significantly reduced by 6%. Concentrations of palmitic, stearic and oleic acids were increased, whereas linoleic acid was reduced. Stable genotypes, that were least responsive to heat stress, were identified for seed yield (MO genotypes 6, 8 and 12), oil concentration (MO genotypes 8 and 10), and oleic and linoleic acid concentration (HO genotype 4 and MO genotype 11). No single genotype was stable for all traits.
Keywords: grain-filling, oil quality, sunflower, temperature, yield components