Changing climatic conditions are becoming one of the major challenges facing agricultural production globally as demand for staple foods increases. Wheat is one of the most important foods consumed globally, grown in semi-arid and temperate environments where drought negatively affects wheat production.

This study was designed to identify and select drought-tolerant bread wheat genotypes using morpho-physiological and molecular approaches. The aim was to quantify the effects of two drought intensities by withholding watering for 45 and 65% of the volumetric soil moisture content (VSMC) for 14 days after anthesis to identify changes associated with drought tolerance. Increased malondialdehyde (MDA) accumulation resulted in extinguishing of chlorophyll that can be an indicator of stress. Drought tolerant genotypes tended to increase carotenoids that could play a vital role in resisting water shortage stress, while severe drought stress at 65% of VSMC induced a significant decrease of the chloroplyll a content in drought-sensitive genotype.

The expression of ascorbate peroxidase (APX) and glutathione S-transferases (GST) in response to drought was genotype-specific and dependent on drought intensity. Results suggested that oxidative stress was induced by drought, and that besides catalase (CAT), the enzymes of the AsA-GSH cycle (glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR)), appear to function as an important component of the antioxidative defence system under severe drought stress.

The results of gene expression of the wheat dehydrins (DHN5 and WZY2) showed that at severe drought stress those two genes were highly expressed in drought-tolerant genotype (Bubnjar), compared to other genotypes. Compiling all data, it can be concluded that drought-tolerant and medium-tolerant wheat genotypes have better response to drought stress that is corresponding to decreasing oxidative injury by earlier induction of the antioxidant system, compared to drought-sensitive genotypes.

Wheat breeders should use these findings in selection by combining information from physiological, biochemical, molecular and morphological results that will help to identify the most drought-tolerant genotypes having the highest number of genes controlling drought tolerance.