Genetic variability in sunflower cultivars under drought. I. Yield relationships

Abstract

Field experiments were conducted between 1981 and 1983 at Cordoba, Spain, to evaluate the yield responses to drought of 53 sunflower genotypes. There was substantial variability among genotypes both in dryland yield and in yield potential, estimated as the yield under frequent irrigation. No association was found between yield potential and the drought susceptibility index, suggesting that drought resistance and high yield potential may be combined in improved sunflower cultivars. Water deficits reduced harvest index (HI) in all genotypes but the decrease in HI varied among genotypes. Excellent correlations were found between HI and grain yield under dryland conditions for genotypes with similar length of season. The reduction in HI due to water deficits was mostly due to adjustments in seed number with less variation in individual seed weight. In turn, the reduction in seed number was due to a combination of reduced head size and of the area having viable seeds. The length of season of the genotypes apparently affected the yield component adjustments in response to water deficits.