Recently, wheat made headlines as this year’s production is forecast to be the lowest in five years, due to extreme weather in most of the primary wheat growing areas of Northern Europe, Canada and Asia.
Wheat is in the news again – this time in a positive light – with an announcement that an international group of researchers has finally published a detailed description of the genome of bread wheat.
The new generation of allergen-free wheat for bakers?
“Until now, we couldn’t determine the genes that encoded those proteins,” said Odd-Arne Olsen from the Norwegian University of Life Sciences. His team has now identified 356 such genes of the specific proteins responsible, of which 127 are new to science and 222 were known, but had been incorrectly sequenced.
The team also found that wheat produces more of the allergens behind celiac disease when grown at high temperatures, which suggests that baked goods might become more allergenic as the world continues to warm.
Understanding the genes gives breeders a better chance in creating less-allergenic varieties.
As with all things though, it will not happen overnight.
Olsen noted the same proteins behind wheat allergies also determine the baking quality of flour.
Similarly, Eversole noted that wheat varieties that contain more protein also tend to grow at lower yields.
“Having breeders take the information we’ve provided to develop varieties that are more adapted to local areas is really, we think, the foundation of feeding our population in the future,” said Eversole.
It has been a massive undertaking, involving the efforts of 202 authors from 73 research agencies in 20 countries, and 13 years of collaborative research, at a cost of around $75m.
To understand the enormity of the task, the genome of Arabidopsis – the first plant to be sequenced – contains 135 million DNA letters, the human genome contains three billion and bread wheat has 16 billion, five times the size of the human genetic code.
To make it even more complicated, modern bread wheat has three pairs of every chromosome, one from each of its ancestral grasses.
About 500,000 years ago, two species of wild grass hybridized with each other to create what we know as emmer wheat. When humans domesticated this plant, a third grass species inadvertently joined the mix, creating a hexaploid genome.
Moreover, more than 85% of the genome is composed of repeated elements.
Giant jigsaw
“It’s a billion-piece jigsaw puzzle with 90% blue sky and 10% clouds,” said co-author Andrew Sharpe of the University of Saskatchewan, in Canada. “You can imagine putting together a jigsaw puzzle of essentially the same thing.”
A partial mapping of the wheat genome has been discovered, but this is the first time the full genome – with all 21 chromosomes – of the Chinese Spring bread wheat variety has been sequenced.
In the report, published in Science, researchers were able to accurately place 107,891 genes and more than four million molecular markers, as well as identify how and when those genes become active.
“It’s really a miracle that we finished,” said co-author Kellye Eversole, executive director of the International Wheat Genome Sequencing Consortium (IWGSC).
Breadwinner
While wheat is the largest single food source on Earth, to meet future demands of a projected world population of 9.6 billion by 2050, wheat productivity needs to increase by 1.6% each year.
Not fully understanding the gene (known as TraesCS3B01G608800) means wheat production has lagged behind and the crop’s profitability has dropped.
The discovery is expected to reduce the time it takes to develop new disease-resistant wheat strains by about one-third, as well as predict how new varieties will perform in the field, even before the seed is in the ground. It will also help breeders develop wheat that does well in drought, saline soil, high humidity or other previously inhospitable climates.
The work is also paving the way to identify the specific genes responsible for wheat allergies and sensitivity.
“How do you thank a team of scientists who persevered and succeeded in sequencing the wheat genome and changed wheat breeding forever?” said Stephen Baenziger, University of Nebraska–Lincoln Professor and Nebraska Wheat Growers Presidential Chair.
“Perhaps it is not with the words of a scientist, but with the smiles of well-nourished children and their families whose lives have been changed for the better.”
All IWGSC reference sequence resources are publicly available at the IWGSC data repository at URGI-INRA Versailles and at other international scientific databases such as GrainGenes and Ensembl Plant.
Study:
“Shifting the limits in wheat research and breeding using a fully annotated reference genome”
Authors: The International Wheat Genome Sequencing Consortium (IWGSC): Rudi Appels, Kellye Eversole, Catherine Feuillet, et al.
Science, August 17, 2018: Vol. 361, Issue 6403
DOI: 10.1126/science.aar7191
The IWGSC is a non-profit organization that was founded in 2005. Today, it has 2,400 members in 68 countries, comprising wheat growers, plant scientists, and public and private breeders.
The goal of the IWGSC is to make a high-quality genome sequence of bread wheat publicly available to pave the way to develop improved varieties.