Crop productivity as related to single-plant traits at key phenological stages in durum wheat

Selection based on single plants is a necessary step during early generations in breeding programs, where populations are still heterogeneous. A major problem is that individual plant performance is rather independent of crop performance, and there are few studies indicating physiological traits in individual plants that are reliable to select for to increase crop yield. In this context we aimed to find out whether it is possible to identify morpho-physiological traits in single spaced plants that might be trustworthily used for selecting in early generations for improving crop performance in durum wheat. We have grown during two seasons both isolated plants and dense populations of the same durum wheat genotypes. Isolated plants were sown at <20 plants m−2 while crop populations were grown at 200 plants m−2 during the first experiment and 400 plants m−2 during the second one. Several traits (57 and 114 in the first and second experiments, respectively) were measured or estimated at different steps during the crop cycle in both conditions. Both, crop and individual plant yields were better explained by the number of grains than by the average weight of the grains. As expected, there was no relationship between crop yield and yield of the individual plants. Yield components and other traits measured in individual plants at maturity did not relate well with crop yield. However, specific leaf weight and spike partitioning of isolated plants determined at anthesis exhibited clear trends to be positively related to crop yield. Both traits are dense independent and may be potentially useful selection criteria, if surrogates to determine them more easily or molecular markers become available.

► We tried to identify morpho-physiological traits in single spaced durum wheat plants that might be useful for selection in early generations for improving crop performance.
► None of the many traits studied in isolated individual plants could unequivocally be pointed as a definite selection criterion.
► However, crop yield was positively related to both specific leaf weight and spike partitioning of isolated plants at anthesis.
► Both traits are dense-independent and may impact on grain yield.