Physiological attributes associated with yield and stability in selected lines of a durum wheat population

Further increasing yield potential remains one of the main objectives of wheat breeding, even in stressful environments. In general, past genetic gains were associated with increases in harvest index, and future gains should be related to greater biomass. Identifying genetic sources for such improvement may be relevant. Researchers of TRITIMED identified DH lines of durum wheat apparently possessing not only high yield potential but also good yield stability. We aimed to determine physiological attributes responsible for yield and stability among a set of genotypes derived from two parents (Cham 1 and Lahn) and four of the most promising lines of the DH population (2401, 2408, 2410, 2517). Seven field trials were carried out within the Mediterranean agricultural region of the Ebro Valley, under a wide range of conditions (ca 2-10 mg ha(-1)). In four of these experiments, sub-plots were included with source-sink manipulations imposed after anthesis. Cham 1, a cultivar known for high yields in semi-arid conditions, showed the highest yield potential. Although it showed less yield stability than Lahn, even under the lowest yielding conditions its yield was not significantly lower than that of Lahn. RILs 2408, 2410, 2004 and 2517 slightly outyielded Lahn in high-yielding conditions, but under poorer environments they tended to yield less. Interestingly, yield differences were closely related to their biomass rather than harvest index. Thus yield differences relating to the number of grains per m(2) were due to differences in spike dry matter at anthesis, reflecting in part genotypic differences in crop growth from jointing to anthesis. In general grain weight did not respond to spike trimming after anthesis, although in two experiments the grain weight of Cham 1 did so. Thus, even the highest-yielding cultivar possessed grains that overall seemed more limited by its constitutive capacity to grow than by the availability of resources to reach this capacity (though occasionally they may be co-limited). Overall, the most interesting feature was the empirical evidence that improvement of biomass within elite material is a worthwhile objective.