Biochemical Indices of Drought Tolerance in Wheat (Triticum aestivum L.) at Early Seedling Stage

Availability of biochemical markers to check drought tolerance at seedling stage could help in escalating selection intensity in breeding drought-tolerant wheat (Triticum aestivum L.) varieties. For this purpose, four wheat genotypes with varying degrees of drought tolerance were used to reveal the biochemical indices of drought tolerance at the seedling stage. Relatively tolerant genotypes (Sitta, Sarsabz and Fareed) accumulated higher peroxidase, sharply increased superoxide dismutase (SOD) (Fareed) and catalase (CAT) (in Sitta and Fareed) activities and total phenolics under drought stress. Drought-tolerant genotypes also kept higher ascorbate compared with the sensitive genotypes under stress and nonstress conditions while ascorbate peroxidase (APX) activity was not affected by drought stress. However, in the relatively sensitive genotype Inqalab-91, drought caused a decrease in peroxidase (POD) and ascorbate and 'enhanced the proteases, APX and membrane lipid peroxidation measured as malondialdehyde (MDA) content. In this sensitive genotype, MDA level was above two-fold compared with the control. Drought stress induced compromised antioxidant activities and enhanced protein, lipid degradation played a central role in drought sensitivity while accumulation of higher antioxidants, i.e., CAT, PODs, SOD and ascorbate resulting in better protection to biomolecules contributed significantly in conferring drought tolerance in wheat. Thus, antioxidants and stress markers can be efficiently and economically used as biochemical indices to screen or to enrich wheat germplasm for drought tolerance at the early seedling stage.