Uncovering the dispersion history, adaptive evolution and selection of wheat in China

Abstract

SummaryWheat was introduced to China approximately 4500 years ago, where it adapted over a span of time to various environments in agro‐ecological growing zones. We investigated 717 Chinese and 14 Iranian/Turkish geographically diverse, locally adapted wheat landraces with 27 933 DArTseq (for 717 landraces) and 312 831 Wheat660K (for a subset of 285 landraces) markers. This study highlights the adaptive evolutionary history of wheat cultivation in China. Environmental stresses and independent selection efforts have resulted in considerable genome‐wide divergence at the population level in Chinese wheat landraces. In total, 148 regions of the wheat genome show signs of selection in at least one geographic area. Our data show adaptive events across geographic areas, from the xeric northwest to the mesic south, along and among homoeologous chromosomes, with fewer variations in the D genome than in the A and B genomes. Multiple variations in interdependent functional genes such as regulatory and metabolic genes controlling germination and flowering time were characterized, showing clear allelic frequency changes corresponding to the dispersion of wheat in China. Population structure and selection data reveal that Chinese wheat spread from the northwestern Caspian Sea region to South China, adapting during its agricultural trajectory to increasingly mesic and warm climatic areas.

Comparative Population Genomics of Bread Wheat(Triticum aestivum)Reveals Its Cultivation and Breeding History in China

“…After its evolution in the Middle East and Mediterranean regions, bread wheat gradually spread to the rest of the world and was domesticated for human use 10 . China has been cultivating bread wheat for ~4,600 years 11,12 , and has been the largest wheat-producing country for more than two decades. Wheat has been under continuous artificial selection in the diverse ecological zones of China for thousands of years 11,13 ; thus, the domestication and breeding of bread wheat in this country provides unique evolutionary insights into how its genome diversity was used and altered to meet the changing needs of the human population.…”

Phylogenetic and population structural inference from genomic ancestry maintained in present‐day common wheat Chinese landraces

“…More importantly, together with the characterized population structures, the results corroborated the well maintained ancient genomic ancestry within the modern common wheat, especially in those grown in southwestern China (V‐SWAS and IX‐Q&T). Our observed well maintained genomic ancestry indicates that the present landraces in southwest should harbour higher diversity than those grown in other agroecological zones (Appels and Lagudah, ; Wang et al ., ; Zhou et al ., ). As revealed by the exonic SNPs composition, the foregoing expectation is supported by the highest heterozygosity in landraces of V‐SWAS relative to those in other wheat‐growing zones (Zhou et al ., ).…”

“…tauschii (DD) and T. turgidum subsp. dicoccoides (BBAA) is believed to have conserved the population genetic structure of the original hexaploid common wheat (Dvorák et al ., ; Zhao, ; Wang et al ., ; Zhou et al ., ).…”

“…Therefore, research into the genetic structure and diversity of Chinese common wheat populations may provide valuable clues about how the wheat population evolved, spread, and further domesticated in China. Previous studies have mainly focused on populations of modern wheat landraces to characterize and compare the genomic population structure and diversity within extant wheat landraces, which are locally adapted to different wheat‐growing zones in China (Cavanagh et al ., ; Wurschum et al ., ; Zhou et al ., ). These studies have highlighted the adaptive evolutionary history of wheat cultivation and its possible entry into and further dispersal within China.…”

“…Nevertheless, studies on common wheat population evolution in China using ancient wheat DNA have not been reported. Therefore, without data from ancient DNA, those inferred entry sites and following dispersal routes remain contentious (Zhou et al ., ).…”