Carbon isotope discrimination association with yield and test weight in Pacific Northwest–adapted spring and winter wheat

Abstract

Due to considerable influence of environment on yield, breeding for drought tolerance could benefit from focusing on selection of more heritable physiological traits, such as carbon isotope discrimination (as measured by delta, ∆) for indirectly assessing water use efficiency (WUE) of wheat (Triticum aestivum L.). Spring and winter wheat cultivars were assayed for ∆, and these values were used to determine the relationships with performance in over 13 environments in the U.S. Pacific Northwest. The correlation coefficients of ∆ values between the wheat cultivars grown in different environments ranged from 0.11 to 0.73 for both spring and winter wheat. There was significant genotypic variation for ∆ in soft spring and hard winter wheat but not in hard spring and soft winter wheat. The ∆ values were poor indicators of yield for this set of wheat cultivars in most environments, although low values (better WUE) were sometimes correlated with yield. A population of 165 hard spring wheat recombinant inbred lines derived from a cross between two hard spring wheat varieties that differed in ∆ was also screened in low‐rainfall dryland and irrigated environments. High yields in this recombinant inbred population were weakly correlated with high ∆ values or low WUE in most environments.