Indeed, the average yield increase of wheat is stagnating for a few years now. A new international study has cataloged and contextualized the genetic diversity of 487 wheat genotypes originating from large parts of the world with agronomic traits. The map of this rich pool highlights the current knowledge of the ancestry of wheat and opens new avenues within modern selective wheat breeding.
The evolution of wheat is a complex history of hybridization and gene flow events which led to the allohexaploid (with six sets of chromosomes) Triticum aestivum, the species of wheat that we know nowadays as bread wheat. The modern bread wheat originated in the Fertile Crescent about 10,000 years ago, and its gene pool has been shaped by humans as a result of domestication and cultivation. Today, high-yielding varieties of Tritium aestivum can be found all over the world, each type adapted to the particular environment in which it is being grown, making wheat one of the world's three most essential crop species for human calories and protein supply.
The onset of global warming, the growing demand for wheat, and the transitioning of Western farming away from intensive agriculture, are exerting pressure on plant breeders to adapt further and improve modern bread wheat species. However, to select and breed new wheat cultivars with new and improved traits, plant breeders require plants with a genetic variation for selection and combination during the breeding process. A new international study of bread wheat has now revealed knowledge of a vast and rich gene pool for future breeding improvements of Triticum aestivum.
The new study sequenced the exomes of 487 wheat genotypes from 68 countries around the world, including landraces, cultivars, as well as modern varieties. The Leibniz Institute of Plant Genetics and Crop Plant Research (IPK Gatersleben) contributed to this research by providing wheat samples from the Federal Ex situ Gene Bank.
The researchers utilized the Refseqv1.0 reference sequence of the bread wheat landrace "Chinese Spring" which had been published in 2017 by the "International Wheat Genome Sequencing Consortium" (IWGSC), it was possible for the collaborating researchers to compile a comprehensive overview of wheat genomic diversity at the genic, chromosomal and subgenomic levels.
As a result, the researchers were able to refine and expand the model of wheat evolution and to decipher the genetic origins of modern day wheat species. As such, the durum wheat lineage was confirmed as the most likely ancestor of today's bread wheat cultivated germplasm. Moreover, by investigating the selection footprints of wheat, the scientists showcased the effects of range expansion and allelic variants selected since the beginning of wheat domestication.
Another step towards the assembly of the "pan-genome" of wheat is the reported data, the description of all the genes and genetic variations within wheat which will be a valuable resource for plant researchers and wheat breeders alike.
As it stands, the study, however, has shown a rich genetic data resource which can be utilized for improving genetic traits in bread wheat from environmental adaptation to improved yield and disease resistance. Moreover, the results of the study illustrate our knowledge of the ancestry of bread wheat highlighting our cultural history as farmers and plant breeders.
