Yield formation strategies of durum wheat landraces with distinct pattern of dispersal within the Mediterranean basin I: Yield components

This study was undertaken to ascertain whether the pattern of dispersal of durum wheat within the Mediterranean basin is associated with variation in phenology and yield formation strategies. A set of 52 durum wheat landraces, previously genetically characterized as been dispersed by the north or south of the Mediterranean region, were grown in three rainfed sites in a dry-temperate region (Lleida, NE Spain), and crop phenology, yield and yield components were determined. Northern genotypes had a larger number of stems per unit area, but a lower percentage of fertile tillers and fewer grains per spike than southern landraces. Grain yield for the northern dispersal group was mainly related to variations in thousand-kernel weight, while the number of spikes per m2 was the component most highly correlated with yield among southern genotypes. These contrasting yield formation strategies are probably a consequence of the different climates prevalent in the zones of adaptation, and likely conferred adaptive advantages to the genotypes of one or the other group. Our results suggest that gradual changes in yield components occurred during the movement of durum wheat from east to west through the north side of the Mediterranean basin. According to our results, the weight of grains and the number of spikes per unit area may be selection criteria to improve adaptation for the northern and the southern parts of the Mediterranean basin, respectively.