Carbon Isotope Discrimination, Selecting for Productivity and Water Use Efficiency in Wheat.

Available water frequently limits grain productivity of wheat, particularly in western Kansas. Commercial and experimental wheat lines differed in carbon isotope discrimination (Δ¹³C), grain yield and N removed by grain; growing conditions (dry to favorable) affected yield, N removed by grain and
Δ¹³C, as well as interacting with germplasm responses. Wheat grown under more productive conditions resulted in larger
Δ¹³C values; supporting interpretation of
Δ¹³C as a possible indicator of water stress, as well as water use efficiency. A linear relationship between
Δ¹³C and yield was derived from samples collected at dry study sites, which was predictive of yields averaged over multiple environments. However, developing reliable yield predictions from
Δ¹³C would likely require further studies, under controlled field conditions. These studies should also consider δ¹⁵N as an indicator of nitrogen stress, in relation to water stress and use efficiency.