Reduced vegetative growth increases grain yield in spring wheat genotypes in the dryland farming region of north-west China

To understand the co-evolution in yield-related traits with the breeding, selection, and introduction of genotypes for increased grain yield, field experiments were carried out at two sites in the western area of the Loess Plateau in China that differed in hydrothermal conditions. Sixteen genotypes of spring wheat introduced and grown over the past 120 years were compared in terms of their yield and yield-related traits. As the grain yield increased, the spike number per unit area and the grain number per spike increased linearly, but the 1000-kernel weight was not correlated with grain yield. In the more recent genotypes, anthesis was initiated significantly earlier, although the length of the period from anthesis to maturity remained unchanged. Water use and the Effective Use of Water (EUW) for aboveground biomass before anthesis and the contribution of pre-anthesis aboveground biomass to grain yield all decreased as grain yield increased. Soil water content at anthesis was negatively correlated with aboveground biomass at anthesis, but positively correlated with grain yield. Conclusively, breeding in spring wheat over the past century has increased the yield of new genotypes by (1) increasing the number of grains per unit area; (2) shortening the period of vegetative growth; (3) decreasing EUW and the soil water use before anthesis; thereby (4) retaining more soil water and increasing biomass accumulation after anthesis. Future spring wheat breeding for this dryland region should determine whether the time for grain filling from anthesis to maturity can be extended to enable greater use of environmental resources and higher yields.