Wheat speciation and adaptation: perspectives from reticulate evolution

Abstract

Reticulate evolution through the interchanging of genetic components across organisms can impact significantly on the fitness and adaptation of species. Bread wheat (Triticum aestivum subsp. aestivum) is one of the most important crops in the world. Allopolyploid speciation, frequent hybridization, extensive introgression, and occasional horizontal gene transfer (HGT) have been shaping a typical paradigm of reticulate evolution in bread wheat and its wild relatives, which is likely to have a substantial influence on phenotypic traits and environmental adaptability of bread wheat. In this review, we outlined the evolutionary history of bread wheat and its wild relatives with a highlight on the interspecific hybridization events, demonstrating the reticulate relationship between species/subspecies in the genera Triticum and Aegilops. Furthermore, we discussed the genetic mechanisms and evolutionary significance underlying the introgression of bread wheat and its wild relatives. An in-depth understanding of the evolutionary process of Triticum species should be beneficial to future genetic study and breeding of bread wheat.

Dispersed emergence and protracted domestication of polyploid wheat uncovered by mosaic ancestral haploblock inference

“…In contrast to rice and maize, hexaploid wheat emerged in a field of domesticated tetraploid wheat and interploidy hybrid swarms happened in the early agricultural field 61 . This complicated picture of the early domestication process 2 implying the contributions of interploidy and interspecific gene flow to the evolution of Triticum species might be underestimated previously. Recent evidence of pervasive introgression in wheat 3 , 5 also supported that the bread wheat utilized existing gene pool of tetraploid wheat through interploidy introgression during spreading 7 .…”

“…Genomic introgression, as a result of natural hybridization, is a creative evolutionary force in plants 1 . As one of the staple crops worldwide, the reticulate evolutionary nature of wheat has long been recognized, and pervasive introgressions have been reported among (sub-)species 2 . Recent studies showed that bread wheat received composite introgression from tetraploid relatives 3 – 5 , facilitating its adaptation to diverse environments and resistance to biotic stress 5 , by bringing allelic resources available 6 .…”

“…Shortly after this time, hexaploid wheat ( Triticum aestivum ) was considered to originate from the hybridization between domesticated tetraploid wheat ( Triticum turgidum , BBAA) and wild goatgrass ( Aegilops tauschii , DD) 10 – 12 ; it then took over tetraploid wheat and spread worldwide, arriving in Europe ~8,000 years ago 13 and in China ~4,600 years ago 14 , successfully becoming a worldwide staple crop. During this domestication process of polyploid wheats, interploidy hybridization is supposed to be involved in the origins of at least two subspecies of T. turgidum and two subspecies of T. aestivum 2 . Diversity level of ancestries was high even within subspecies, as showed by the putative multiregional origin hypothesis of the domesticated emmer wheat 9 , 15 .…”

Population genomics unravels the Holocene history of Triticum-Aegilops species

“…Fueled by the landmark bread wheat reference genome 12 , recent studies have reconstructed the phylogeny of Triticum-Aegilops species 13,14 , characterized the population structure of modern wheat 9,13,[15][16][17] , and identified historical gene flow from wild populations to bread wheat 13,14,16,18,19 . However, the population history of wheats (bread wheat and its wild relatives, or Triticum-Aegilops species) is largely incomplete, particularly the spatiotemporal dynamics of bread wheat emergence and dispersal, together with the genetic and ecological interaction between bread wheat and its wild relatives, remain elusive 6,20,21 .…”

A Wheat TaTOE1-B1 Transcript TaTOE1-B1-3 Can Delay the Flowering Time of Transgenic Arabidopsis

“…During the long course of evolution, plants have developed powerful adaptive mechanisms to cope with a variety of environments [ 1 , 2 ]. Flowering is an important stage in the process of plant life generation.…”