Differential Activity and Expression Profile of Antioxidant Enzymes and Physiological Changes in Wheat (Triticum aestivum L.) Under Drought.

Wheat crop may experience water deficit at crucial stages during its life cycle, which induces oxidative stress in the plants. The antioxidant status of the plant plays an important role in providing tolerance against the water stress. The objective of this study was to investigate the impact of water stress on physiological traits, antioxidant activity and transcript profile of antioxidant enzyme related genes in four wheat genotypes (C306, AKAW3717, HD2687, PBW343) at three crucial stages of plants under medium (75% of field capacity) and severe stress (45% of field capacity) in pots. Drought was applied by withholding water for 10 days at a particular growth stage viz. tillering, anthesis and 15 days after anthesis (15DAA). For physiological traits, a highly significant effect of water stress at a particular stage and genotypic variations for resistance to drought tolerance was observed. Under severe water stress, the malondialdehyde (MDA) content increased while the relative water content (RWC) and chlorophyll index decreased significantly in all the genotypes. The drought susceptibility index (DSI) of the genotypes varied from 0.18 to 1.9. The drought treatment at the tillering and anthesis stages was found more sensitive in terms of reduction in thousand grain weight (TGW) and grain yield. Antioxidant enzyme activities [superoxide dismutase (SOD) and peroxidase (POX)] increased with the decrease in osmotic potential in drought tolerant genotypes C306 and AKAW3717. Moreover, the transcript profile of Mn-SOD upregulated significantly and was consistent with the trend of the variation in SOD activity, which suggests that Mn-SOD might play an important role in drought tolerance.