These experiments were conducted to evaluate the role of thiourea on accumulation of osmoprotectants and antioxidants in the salt stressed maize roots and callus of maize hybrids. Medium supplementation of 400 µM thiourea was applied on two maize hybrids; 33M15 and DK6789. The maize hybrid 33M15 performed better than DK6789. Fifteen days older plants and immature embryo were subjected to medium supplemented with thiourea and salt (120 mM NaCl) separately and in combination. Salt stress suppressed plant growth, callus induction, and regeneration percentage due to increased oxidative damage. Thiourea medium supplementation up regulated antioxidant activity and improved morphological attributes. Thus, thiourea medium supplementation significantly improved salinity tolerance of hybrid maize plants and callus. This improvement was estimated by reduced hydrogen peroxide, malondialdehyde, and total free amino acids. Altered activities of antioxidant enzymes as well as increased osmolytes and pigments accumulation under saline regimes also played an important role in salt tolerance. So thiourea supplementation could be a great achievement towards maize tissue culture and advanced techniques that require regenerable callus. Thiourea improved callus quantity and quality (in terms of regenerable) many folds over the control.

Keywords: Maize, thiourea, salt stress, growth, medium supplementation, regenerable.