Water‐Use Efficiency and Carbon Isotope Discrimination in Wheat

Abstract

Drought stress is one of the most limiting factors to crop production in semiarid regions. Improved water‐use efficiency (WUE) could provide breeding programs with a means to improve adaptation to drought‐prone environments. Carbon isotope discrimination (Δ) has been proposed as a criterion to select for improved WUE. This study evaluates differences in total dry matter (TDM), WUE (TDM/transpiration), and Δ of flag leaves of landrace and modern wheat ( Triticum aestivum L.) genotypes grown in pots in a well‐watered (wet) and in a drought‐stressed (dry) experiment for 2 yr. The wheat genotypes were also grown in wet and dry field conditions. In the pot experiments, average WUE of the genotypes varied from 2.85 to 4.41 g dry matter kg −1 water in the wet experiment and from 3.08 to 4.53 in the dry experiment. The mean values of Δ were 21.7 ✕ 1O −10 for the wet pot experiment and 21.6 ✕ 10 −3 for the dry pot experiment. The tall landrace genotypes had greater TDM and WUE, but were later in maturity than the modern dwarf and semi‐dwarf genotypes. Values of Δ associated with different genotypes were negatively correlated with WUE. Broad‐sense heritabilities for WUE and Δ were 93 and 90%, respectively, in the pot experiments. In the dry field experiments, Δ was positively associated with above‐ground dry matter and grain yield in both years. In the wet field experiments, there was a positive correlation between Δ and grain yield only in 1988. Broad‐sense heritabilities for Δ were 72% for wet field conditions and 74% for dry field conditions. These observations indicate that selection for C isotope discrimination, under either wet or dry conditions, can improve water use efficiency in wheat.