Selection response for carbon isotope discrimination in a Triticum polonicum×T. durum cross: Potential interest for improvement of water efficiency in durum wheat

Abstract

AbstractThis study has been conducted to evaluate the usefulness of carbon isotope discrimination (δ) in mature kernels as a criterion for the improvement of water‐use efficiency and yield under drought in durum wheat. For this purpose, Triticum durum‘Om Rabi 5’ was crossed with T. polonicum pseudochrysospermum 9 (Tp9) which has been found to be more drought tolerant and to have a lower carbon isotope discrimination value of the grain. The F2 population showed a wide segregation for carbon isotope discrimination. Further, divergent selections (selection of plants most different in carbon isotope discrimination) were made among individual F2 plants, and for carbon isotope discrimination in F3 progenies under field conditions. Selected F3 and F4 progenies were evaluated under field conditions for morphological and agronomical traits. Broad‐sense heritability (h2b), response to selection and realized heritability (h2r) were high. The narrow‐sense heritability (h2n= 0.37 ± 0.047) indicated that additive and dominance effects were involved in the genetic control of carbon isotope discrimination. Negative correlations were noted between carbon isotope discrimination and grain yield and between carbon isotope discrimination and biomass yield within years and generations. An explanation of this result is attempted by analysing the relationships between carbon isotope discrimination and several phenological and morphological traits influencing the water‐use efficiency. The divergent groups selected for low and high carbon isotope discrimination exhibited significant differences for days to heading, plant height, shape of the spike and number of spikelets per spike. Correlations were also found between carbon isotope discrimination and plant height, harvest index, shape of the spike, spike length, and number of spikes per plant. The potential use of carbon isotope discrimination as a criterion for the improvement of water‐use efficiency in durum wheat is discussed by considering the genetics of this trait (variability, heritability, response to selection) and also the associations with phenological and morphological traits.