Growth plasticity and yield formation in dryland wheat (Triticum aestivum) under artificial selection

Dryland wheat has gone through double selections, including natural and artificial selection, in the evolutionary process. During this process, artificial selection played a key role in variety domestication and improvement. This paper summarized a few relatively independent but interrelated issues including evolutionary characteristics, physiological plasticity, morphological plasticity and population attribute transition in dryland wheat under artificial selection. It provided an overview on physiological and ecological mechanism of dryland wheat adapting to stress conditions, and an outline of wheat evolution route. In the long-term evolutionary history of dryland wheat from diploid to hexaploid, natural selection acted as a key role for wheat adaptation to stress environments. With the intervention of artificial selection, the yield-oriented phenotyping has been continuously strengthened, and morphological characteristics of wheat tended to display a fine adaptation to adverse environments at population level. As a product of artificial selection, water and nutrient use efficiencies were improved constantly, and biomass allocation pattern showed the characteristics of lowering below-ground parts and increasing above-ground parts. In the meantime, the tolerance to density and high temperature stresses tended to be enhanced, while photosynthetic rate per unit area was decreased gradually. Dryland wheat production was a complex population process, rather than a simple individual performance. Artificial selection increased population fitness and individual reproductive allocation in dryland wheat, which in turn strengthened its coordination with environment, but weakened its attributes of natural population. This paper also drew an outline of dryland wheat evolution, and provided a few suggestions for breeding strategies and cultivation management of dryland wheat under climate change.