Comparative response of drought tolerant and drought sensitive maize genotypes to water stress

Maize genotypes Giza 2 (drought tolerant) and Trihybrid 321 (drought sensitive) were sown in the small pots under laboratory condition. Water stress condition was created by irrigating the pots with polyethylene glycol (PEG) solutions of 0.0, -5, -10 and -20 bars and observations were made on 21-day-old seedlings. The tolerant genotype Giza 2 exhibited lower accumulation of malondialdehyde (MDA) and H2O2 content related to increasing activities of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), and peroxidase compounds (POX, EC 1.11.1.7), under water stress conditions. The higher water retention capacity and lower membrane injury made Giza 2 more drought tolerant. Drought stress was resulted by accumulation of gylycinebetain (GB) and free proline (PRO) in both cultivars. The magnitude of increase in both omsolytes was higher in Giza 2 than in Trihybrid 321. We suggest that free proline and gylycinebetaine accumulation in the leaves can be used as the possible indicator for drought tolerance in maize genotypes. Water deficits induced an increased level of photosynthetic activity ((CO2)-C-14-fixation) in Giza 2 than Trihybrid 321. Therefore, it can be concluded that the stress tolerance mechanism exists at seedling stage of maize genotypes. The Giza 2 is comparatively tolerant to water stress owing to the lower increase in H2O2 and MDA content along with higher increase in PRO, GB accumulation, photosynthetic efficiency, SOD, CAT and POX activities. The higher membrane stability index and high water retention capacity might have also imparted water stress tolerance in Giza 2. Further, Trihybrid 321 was also able to resist water stress to some extent via the above adjustments.