Field Crops Research 125 (2012) 49–60 Contents lists available at SciVerse ScienceDirect Field Crops Research jou rn al h om epage: www.elsevier.com/locate/fcr Constitutive differences in water use efficiency between two durum wheat cultivars Fulvia Rizza a,∗ , Jaleh Ghashghaie b , Sylvie Meyer c , Loredana Matteu d , Anna Maria Mastrangelo d , Franz-Werner Badeck e a CRA-GPG Centro di Ricerca per la Genomica e la Postgenomica Animale e Vegetale, Via S. Protaso, 302, I-29017 Fiorenzuola d’Arda (PC), Italy b Laboratoire d’Ecologie, Systématique et Evolution (ESE), CNRS AgroParisTech-UMR 8079, Bâtiment 362, Université de Paris-Sud (XI), F-91405 Orsay Cedex, France c Univ. Paris Diderot, Sorbonne Paris Cité, F-75475 Paris, France d CRA-CER Centro di Ricerca per la Cerealicoltura, SS 16 Km 675, I-71122 Foggia, Italy e Potsdam Institute for Climate Impact Research (PIK) PF 60 12 03, D-14412 Potsdam, Germany a r t i c l e i n f o Article history: Received 23 January 2011 Received in revised form 3 September 2011 Accepted 3 September 2011 Keywords: Water use efficiency Durum wheat Carbon isotope discrimination Growth Stomatal conductance Constitutive traits a b s t r a c t This work was focused on the physiological analysis of the response to water availability in two durum wheat (Triticum turgidum var. durum) parents of a mapping population, Cappelli and Ofanto, represent- ing an old and a modern cultivar, respectively. We investigated if the two parents are constitutively different for traits related to water use efficiency (WUE), a key step to prepare further studies on the large segregating population. Integrated WUE, as recorded by grain ı 13 C, was studied in a 3-year field experiment conducted at Foggia (southern Italy) under irrigated and non-irrigated conditions. A growth chamber experiment was carried out to analyse the cultivars, at leaf and whole plant level in the vegeta- tive growth phase under well watered and drought conditions. All measures consistently showed a higher WUE of the variety Cappelli than Ofanto. This trait was associated with lower stomatal conductance over a range of relative soil water contents tested in the growth chamber experiment. Carbon isotope discrim- ination (CID) was confirmed as useful indicator of WUE when measured in grains harvested in the field trials. In addition, the consistent results obtained by CID analysis in the vegetative organs harvested in the growth chamber experiment, can facilitate the development of opportune phenotying approaches that, in perspective, can be employed for high sample numbers, as required for studies of the segregating population. Traits related to growth and biomass allocation in the map parents, indicative of different adaptive strategies for resource use of Cappelli and Ofanto, were also analysed. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Improving water use efficiency (WUE) in agriculture appears as an urgent imperative in a scenario of increased needs to save water (Condon et al., 2004; Easterling et al., 2007). WUE, expressed as the capacity of a crop to produce biomass per unit of water evapotran- spired, has been identified as a major component of yield, together with water use (WU), the total amount of water used by the crop and harvest index (HI), the grain fraction of aboveground biomass (Passioura, 1977). The relative importance of WU and WUE is depen- dent on the level of water availability in the soil (Araus et al., 2002; Abbreviations: A, leaf net CO2 assimilation; Ca, ambient air CO2 concentration; C i , CO2 concentration in leaf internal air spaces; CID, carbon isotope discrimination; E, leaf level transpiration; gsw, stomatal conductance for water vapour; I, irrigated; NI, non-irrigated; RSWC, relative soil water content; WU, water use; WUE, water use efficiency. ∗ Corresponding author. Fax: +39 0523 983750. E-mail address: fulvia.rizza@entecra.it (F. Rizza). Condon et al., 2002; Blum, 2009). The meaning of WUE, as a compar- ative measure of plant productivity per unit of water used, depends on the unit with which productivity (photosynthesis or biomass accumulation) and WU (transpiration, evapotranspiration or pre- cipitation/irrigation) are expressed, at leaf, plant or canopy level (Salisbury, 1996; see Table 1 for the variants used in the current paper). The relationship between WUE and yield is largely affected by the developmental phase at which WUE is measured. Due to the complex interactions of mechanisms responding to water deficit during the crop cycle, the correspondence among evaluations car- ried out at different developmental phases is not easily predictable. For example, the genotypic differences among barley landraces of different origin observed in soil-pots at the whole plant level by WUE BP (the ratio of plant dry matter to total water transpired) in the generative phase were only partially in accordance with the results obtained for the vegetative phase (Krzeminska and Gorny, 2003). Thus, WUE can vary throughout ontogeny, and to different degrees among genetically non-homogeneous plant materials which may 0378-4290/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.fcr.2011.09.001