Differential Drought Tolerance among Sorghum Genotypes under Polyethylene Glycol-Induced Osmotic Stress at the Seedling Stage

This study evaluated drought tolerance in ten sorghum genotypes using polyethylene glycol (PEG-6000) to simulate osmotic stress. Seeds were germinated for 10 days and a completely randomized design with two moisture regimes 0% PEG and 30% PEG, seedling height, root length, plant height, fresh weight, seedling vigor and drought tolerance indices were assessed. Responses to PEG-induced drought was clearly genotype-dependent. Germination was severely inhibited in sensitive genotypes, declining in V2 (90±1.53% to 70±3.00%), V3 (80±0.10% to 50±2.65%), V4 (100± 0.58% to 70±2.00%) and V5 (100±0.58% to 70±1.00%), whereas V6 and V10 improved under stress (70±2.65% to 90±3.00%). V7 remained stable 100±1.00% in both conditions. Shoot height was markedly reduced in drought-sensitive genotypes, particularly V4 (14.5±8.00 cm to 6.5±3.78 cm), while V10 showed stability (4.6±2.51 cm to 4.8±1.76 cm). V3 maintained best root length (15.7±3.42 cm to 9.2±5.63 cm), indicating superior early root resilience. Fresh biomass was highest in V4 under drought (0.15±0.02 g), whereas V7 declined sharply (0.14±0.01 g to 0.01±0.03 g). V6 and V10 were the most resilient with a DTI of 129 ± 0.00%, while V3 and V4 also demonstrated consistent structural stability. Overall, V3 (Samsorg 46), V4 (Samsorg 48), V6 (Samsorg 52), V7 (Samsorg 53) and V10 (SRN39-2) are promising drought-tolerant genotypes for early-stage screening, which are recommended for further enzymatic and molecular studies on improving photosynthetic efficiency.