PEG-MEDIATED OSMOTIC STRESS RESPONSES OF WHEATBARLEY ADDITION LINES

Abstract

Photosynthetic responses of three wheat-barley addition (add) lines exposed to PEG-induced drought stress and under rewatering period were investigated in order to improve wheat drought tolerance by the help of barley chromosomes. The wheat-barley disomic addition lines (2H, 3H, 4H) the wheat line (Triticum aestivum L. cv. ’Mv9kr1’) were found to have better responses to osmotic stress relative to the parental barley cultivar (Hordeum vulgare L. cv. ’Igri’). Addition lines with 2H and 4H chromosome from barley used similar strategy of acclimation to osmotic stress. These lines were able to avoid drastic water loss as well as exhibiting only a slight decrease in stomatal conductance (gs) in contrast to barley. At the same time, photosynthetic processes in 4H addition seemed to be more sensitive to the decreased relative water content (RWC) of leaves caused by 21% PEG resulting reduction in stomatal to non-stomatal limitation ratio and impaired recovery ability. 3H addition line could be characterized as the most dehydration tolerant among the examined lines on the basis of water wasting responses shown by high gs, decreased intrinsic water use efficiency and more successfully sustained shoot biomass production in contrast to root. Changes in Y(II) parameters were moderate in the addition lines indicating that the electron transport processes were not damaged by osmotic stress. Our results suggest that wheat line also avoided being dehydrated similar to 2H and 4H add but the relatively high RWC under severe water deficit was primarily due to the pronounced stomatal closure. Changes in shoot-root ratio and net CO2 assimilation rate (PN) was also similar to those in 4H add. Although the maintained root growth and strong decreased gs may be the indicators of drought avoidance in barley, in spite of these traits low RWC was observed which contributed to the significantly impaired PN primarily limited by the non-stomatal processes. Considering to drought sensibility, we concluded that barley genotype Igri is not the most suitable gene source for improving water stress tolerance of wheat but 2H addition line seemed to be more resistant to osmotic treatments than wheat and could be used in wheat breeding programs in the future.