Morphophysiological and Biochemical Screening of Bread Wheat Genotypes for Drought Tolerance in Semi-Arid Soils of Dera Ismail Khan, Pakistan

In semi-arid regions, drought is a major factor limiting wheat production and thus identification of drought tolerant genotypes is a key trait in wheat improvement. This study aimed to compare the morphophysiological and biochemical responses of two bread wheat (Triticum aestivum L.) cultivars, Pakistan 2013 and Gomal 2008 under control (80–90% field capacity), moderate drought (50–60%) and severe drought (30–40%). The experiment was laid out in a factorial design with five biological replicates/treatment combination. The plant growth parameters and biomass, relative water content (RWC), chlorophyll, electrolyte leakage, proline, soluble sugars, soluble protein, malondialdehyde (MDA) and antioxidant enzyme activities were measured. Drought had a significant impact on all measured traits, and significant cultivar × drought interactions (P < 0.001). Drought caused a reduction of 40.8% and 59.4% in dry mass of Pakistan 2013 and Gomal 2008 as compared to their controls respectively. Pakistan 2013 maintained higher RWC (69.0%) and total chlorophyll (1.53 mg g⁻¹ FW) than Gomal 2008 (56.0% and 1.07 mg g⁻¹ FW, respectively). The findings also showed that Pakistan 2013 had higher levels of proline and soluble sugars and also had reduced MDA contents as well as electrolyte leakage. Under moderate stress, the activities of antioxidant enzymes were found to be induced and then under severe drought, it was decreased in Pakistan 2013 but increased in Gomal 2008. In Pakistan 2013, the activity of SOD was 126.0 U mg⁻¹ protein while in Gomal 2008 it was 93.0 U mg⁻¹ protein under severe drought condition. The integrated trait analysis thus revealed that Pakistan 2013 was drought tolerant and Gomal 2008 was drought sensitive. Maintenance of tissue hydration, chlorophyll, osmotic adjustment, membrane stability and antioxidant defense seemed to be important mechanisms that played a role in drought tolerance. The traits might be useful for using as selection criteria for screening wheat germplasm that is adapted to water limited, semi-arid environments.