Response of sunflower (Helianthus annuus L) genotypes to PEG-mediated water stress

Drought tolerance of two sunflower (Helianthus annuus L.) genotypes, cultivated cultivar 1114 and interspecific line H. annuus x H. mollis, was studied under laboratory conditions using PEG-6000. Four levels of osmotic stress (-0.4, -0.6, -0.8 and -1.0 MPa) were created and performances were monitored against a control. Physiological and biochemical stress determining parameters such as malondialdechyde (MDA), proline content, and hydrogen peroxide (H2O2) were compared between seedlings of both genotypes. The results indicated that both genotypes have similar responses at four osmotic potentials for all traits studied. All seedling growth parameters such as germination percentage, root length, shoot length, root and shoot dry weight decreased with increasing osmotic stress. MDA, proline, and H2O2 were found to be increased at different osmotic gradients in comparison to control. Cultivar 1114 was less affected than the interspecific line under these stress conditions. The data observed in the experiments revealed that perennial wild H. mollis can hardly be considered to be an excellent candidate of drought tolerance genes.