Unravelling the relationship between adaptation pattern and yield formation strategies in Mediterranean durum wheat landraces

Understanding the environmental and genetic factors behind the adaptation of landraces to different environments may help design breeding strategies and to promote yield improvement. Based on previous results that showed a differential frequency of alleles associated with important agronomic traits in landraces that originated in the east (EM) and the west (WM) of the Mediterranean Basin, this study analysed their patterns of adaptation and the influence this adaptation has on yield formation strategies. Thirteen and thirty-one genotypes selected according to their membership coefficient (q>0.900) from the EM and the WM genetic subpopulations, respectively, were tested during six crop seasons under rainfed Mediterranean conditions. Yearly yields ranged from 3173 to 4917 kg/ha. EM landraces showed more spikes per unit area, while WM ones showed consistently taller plants, larger cycle length to anthesis, a shorter grain filling period, a higher grain filling rate and heavier grains. The contrasting pattern of adaptation of the two subpopulations was based on a differential ability to use the water available before and after anthesis. The yield of EM landraces, originated in the warmest and driest area of the Mediterranean basin, relied mostly on water input before anthesis, which was beneficial for spike production and for the accumulation of water-soluble carbohydrates in the stems prior to anthesis, to be remobilized to grains during grain filling. WM landraces performed better in environments with high water input during grain filling, which was efficiently used to increase grain setting and produce heavy grains. EM landraces could be used in breeding to improve the adaptation of modern varieties to terminal drought.