Water Use Efficiency, Transpiration Efficiency, and Uptake Efficiency of Wheat during Drought

Improving grain performance under water-limited conditions essentially depends on the knowledge of water–yield relationships. The current project was set up to make a field evaluation of relations among grain yield, water use efficiency (WUE), and its components, i.e., transpiration efficiency (TE), uptake efficiency (UE), and harvest index (HI) in bread wheat (Triticum aestivum L.) genotypes. Eight bread wheat genotypes and four water levels (WLs) based on evapotranspiration (ET; WL1, supplying 100% of ET water, to WL4, supplying 25% of ET water) were included in 3-yr experiments. The experiments were conducted under a line-source sprinkler irrigation system. The results of regression analysis revealed that grain yield, WUE, HI, TE, and UE showed linear regression lines against ET. These regression lines ascended for grain yield, WUE, HI, and UE but descended for TE. The best-fit model between WUE and its components was linear and showed an ascending trend for HI and UE but descending trend for TE. The results of this experiment showed that an increase in TE could improve the WUE in wheat genotypes considering that HI is high. That is, applying selection for both TE and HI under water-stress conditions might give the best results to improve WUE in breeding programs.