UV-B Priming of Oryza sativa Seeds Augments the Innate Tolerance Potential in a Tolerant Variety more Effectively Toward NaCl and PEG Stressors

Abstract

NaCl and polyethylene glycol-6000 (PEG) stressors are the major limitation factors for successful seedling establishment in rice. The present study was carried out to investigate the role of UV-B priming on the augmentation of stress tolerance in tolerant and sensitive rice seedlings exposed to NaCl and PEG stresses. The result shows that the severity of drought than salinity stress was experienced by emerging rice seedlings as evidenced from increased content of H2O2, O2− and MDA. However, the seed priming with UV-B results in the enhanced production of defense agents, there by activating innate tolerance potential of the seedlings. UV-B priming reduces excess ROS accumulation during NaCl and PEG stresses and thus eliminates the chance of oxidative stress in the rice seedlings. This was possible by enhancing the crucial role of innate immune system, which imparts tolerance toward NaCl and PEG stresses. UV-B seed priming maintained maximal photochemical efficiency of PSI and PSII as well as mitochondrial activity of tolerant and sensitive varieties under NaCl and PEG stresses due to the increased activity of osmolytes and non-enzymatic antioxidants as well as induced expression of enzymatic antioxidants (Cu/Zn SOD, CatA and APx1) and stress-related proteins (Hsp90 and Group3 LEA) in tolerant variety at large, followed by sensitive variety.