Evaluation of four screening techniques for drought resistance and their relationship to yield reduction ratio in wheat

Drought is one of the important factors limiting crop production in arid and semi-arid regions. Four drought resistance criteria, consisting of canopy temperature, stomatal resistance, transpiring area and rate of water loss by excised-leaves were examined in two experiments conducted in optimum and stress moisture conditions in 1995. A randomized complete block design with four replications and six genotypes was used for each experiment. Under optimum moisture conditions, there was a significant difference in canopy temperature at midday between drought resistant and drought sensitive genotypes. A significant linear relationship was also obtained between this criterion and yield reduction ratio as determined by Y(r) = 1-(Y(s)/Y(p)) (Y(s) and Y(p) = yield under stress and non-stress conditions, respectively), at the ear emergence stage. The only significant difference between cultivars in respect to stomatal resistance in stress conditions was that of adaxial leaf surface in ear emergence stage. No significant linear relationship was obtained between transpiring area and yield reduction ratio. Cultivars differed in respect to rate of water loss (RWL) and initial water content (IWC) in ear emergence and grain filling in stress environment only. Ultimately, three criteria namely canopy temperature, stomatal resistance and RWL, in explicated conditions were recognized as beneficial drought resistance indicators.