Investigation of physiological and biochemical parameters of Turkish wheat cultivars with different ploidy level under drought stress conditions

Drought is one of the most important abiotic stress factors that limit plant growth. Drought stress reduces the yield of many crops including wheat. Therefore, the identification of susceptible and tolerant plant species to drought in particular with wheat is critical for breeders. In this study, responses of against drought stress were investigated in Turkish wheat varieties, which have different ploidies and known as Siyez (Triticum monococcum), Kızıltan-91 (Triticum turgidum durum) and Yüreğir-89 (Triticum aestivum cv.), at the physiological and biochemical level. In leaf and root tissues of wheat species exposed to drought with control groups, physiological (fresh weight, dry weight and length), biochemical (membrane permeability, MDA, H₂O₂, proline and ascorbic acid amount determination) and antioxidant enzyme activity determination (SOD, CAT, APX and GPX) analyzes were performed. It was observed that root lengths of all species increased with the application of drought stress and membrane structure was damaged due to increase of free oxygen species. It was determined that ascorbic acid (non-enzymatic antioxidant) and proline (one of the organic materials synthesized for the least damage of the plant from the changing water status) amonuts increased in root and leaf tissues mostly in Yüreğir-89 and at least in Siyez. The CAT enzyme activity, which enables H2O2 to break down into H2O and O2, has raised in roots of Yüreğir-89 and in leaves of Kızıltan-91. It was found that the activity of SOD enzyme from the first defenses of the plants against the oxidative stress was similarly increased in Yüreğir-89 and Kızıltan-91 varieties. It has been determined that the GPX activity, which is the main protective antioxidant pathway for H2O2 removal, increased most in the Yüreğir-89. In the case of Siyez wheat variety, it was observed that CAT activitiy in the leaf and the SOD activitiy in the root were low. As a result of evaluation of all conducted analyzes, it was determined that Kızıltan-91 and Yüreğir-89 wheat varieties were resistant to drought and Siyez wheat was susceptible to drought. It is thought that strong enzymatic and non-enzymatic antioxidant defense mechanisms in Kızıltan-91 and Yüreğir-89 varieties may be caused by the responses to drought stress. It is also thought that this valuable information about the drought tolerance of wheat species with different chromosome numbers can be used in wheat breeding trials. In addition, it is considered that this thesis has the potential to become a reference source for studies of the identification of wheat species with high survival potential in the future.