Responses of Six Oil Sunflower (Helianthus annuus L) Genotypes to Post-Anthesis Water Deficit

A field experiment was carried out to evaluate the responses of six oil sunflower ( Helianthus annuus L) genotypes namely; Sakha 53, H(A9XRf6), B11, B12, H(A9XRf8) and B20 to drought stress. Plants were subjected to three levels of water: adequate (control), moderate drought and severe drought Water regime was started directly post anthesis by withholding water during seed-filling stage until complete maturity of seeds. Moderate and severe drought decreased plant height and stem diameter of all genotypes, except B11 and B20 which recorded non-significant decrease in plant height under moderate drought. On the other hand, non-significant effect was observed in leaf area in all genotypes except B12 and H(A9XRf8) where a significant decrease was recorded only under severe drought. Yield components (head diameter, seed yield, 100 seed weight, seed husk %, seed kernel % , and oil percentage) responded to drought stress differently according to genotypes. Significant decreases were observed in floral head diameter seed yield, oil percentage and protein content in all genotypes except for the non-significant reduction in seed yield and oil content in Sakha53 and H(A9XRf6) under moderate drought Generally, Skha53 was the most drought-tolerant genotype whereas B11, B12 and B20 exhibited the least tolerance.