Evaluation of variations in physiological and biochemical traits in ancestral and evolutional species of wheat under water deficit stress

Introduction Perception of the genetic diversity in domesticated and wild relatives of a plant species is important for their use in breeding programs. Considering that a large part of wheat cropping fields in Iran is located in arid and semi-arid areas, and that plants adapt to environmental stresses with different strategies, such as changes in antioxidant enzymes. Therefore, it is necessary to study more about the resistant species and the recognition of their mechanism of tolerance. Materials and methods In order to investigate the effect of drought stress on the content of photosynthetic pigments, fresh and dry biomass of roots and shoots and antioxidant enzymes activity in five ancestral and cultivated species of Aegilops and Triticum (Aegiliops tauschii ،Aegiliops speltoides ،Triticum aestivum ، Triticum urartu و Triticum durum), a factorial experiment was conducted based on randomized complete block design with three replications at three levels of normal irrigation (100% FC), medium stress (FC 50%) and severe stress (FC% 25). Results and discussion By mean comparing, the highest activity of CAT, SOD, APX and GPX was observed in severe stress compared to non-stress condition, with an increase of 80, 34, 84 and 29%, respectively. The results showed that the species T. aestivum and T. urartu in terms of SOD, Ae. tauschii for CAT, T.durum for APX and Ae. Speltoides in terms of GPX are considered as candidate species for drought tolerance breeding due to the highest activity of mentioned enzymes in both stresses. Total chlorophyll decreased in moderate and severe stresses by 11.5 and 66%, respectively, however, the two species Ae. speltoides and T. durum showed the lowest reduction compared to normal condition. The carotenoid, which is a non-enzymatic antioxidant, decreased with increasing of drought severity. Not only this reduction was not occurred in T.durum, but also it increased with drought severity. Positive correlation (0.60) was observed between the amount of carotenoid and GPX activity under stress conditions in contrast to non-stress condition. Root dry weight showed a positive correlation (0.81) with APX enzyme under stress conditions. However, in non-stress condition, this correlation was not significant. Conclusions The highest activity of studied enzymes was observed in severe stress compared to non-stress condition. T. aestivum and T. urartu in terms of SOD, Ae. tauschii for CAT, T.durum for APX and Ae. Speltoides in terms of GPX are considered as candidate species for drought tolerance breeding due to the highest activity of mentioned enzymes in both stresses. Total chlorophyll decreased in moderate and severe stresses by 11.5 and 66%, respectively, however, the two species Ae. speltoides and T. durum showed the lowest reduction compared to normal condition. The carotenoid, which is a non-enzymatic antioxidant, decreased with increasing of drought severity. Not only this reduction was not occurred in T.durum, but also it increased with drought severity.