SUNFLOWER (HELIANTHUS ANNUUS L.) RESPONSE TO DROUGHT STRESS AT GERMINATION AND SEEDLING GROWTH STAGES

Response of six sunflower hybrids/breeding lines viz., G-101, SF-187, Hysun-33, Hysun-38, 64-A-93 and S-278 to drought stress imposed at germination and seedling growth stages was investigated in a laboratory experiment (25 +/- 3 degrees C). Five water stress levels of zero (control), -0.35, -0.6, -1.33, and -1.62 MPa were developed using polyethyleneglycol-6000 (PEG-6000). Complete randomized design with three replications was used for this experiment. Germination stress tolerance index (GSI), plant height stress index (PHSI), root length stress index (RLSI) and dry matter stress index (DMSI) were used to evaluate the genotypic response to PEG-induced water stress. Plant height and dry matter stress tolerance indices for all sunflower hybrids decreased with increasing water stress. In contrast, an increase in RLSI was observed in all sunflower hybrids. Sunflower hybrids G-101 and 64-A-93 performed better and were classified as drought tolerant. The variation among hybrids for DMSI was found to be a reliable indicator of drought tolerance in sunflower.