1Comment
The genomes of plant and animal species have been sequenced so fast the world's most widely grown crop would be expected to have been among the first. However, not all species are easy to resolve, and wheat proved so challenging it ended up well down the list, with some scientists questioning if it could be done at all.
Now perseverance and new technologies have paid off, although it took more than 200 scientists from 73 research institutions thirteen years to unravel the wheat genome. Understanding it is essential as we seek to feed an expanding population in an increasingly hostile climate.
This plant alone accounts for almost one in five calories humans consume worldwide, and a similar proportion of the protein. Sequencing wheat will enable the production of better varieties, both through targeted breeding programs and modern transgenic techniques.
The sequencing was announced in six simultaneous papers, an overview in Science and detailed explorations of particular findings in Science Advances and Genome Biology.
Professor Rudi Appels of Murdoch University, first author of the primary paper, said that with the map the sequence provides, looking for genes responsible for a particular trait to clone can be done overnight, where it once took years. Researchers looking for a feature needed in a particular environment can find a variety of wheat that flourishes in similar conditions and home in on the cluster of genes responsible.
Moreover, Appels explained, efforts to breed these genes into new crops will be accelerated, as hybrids can be tested for the presence of desirable genes, rather than waiting for them to grow up to see if they exhibit suitable traits.
Along with higher yields and resistance to drought and disease, Appels hopes the work may bring less allergy-producing breads to our shelves. Although he told IFLScience gluten-free varieties are unrealistic, lower gluten breeds are a different matter.
Appels explained to IFLScience sequencing wheat is not like getting to grips with most other genomes. “Wheat is hexaploid, instead of two copies of each chromosome it has three pairs of everything,” he said. “Each set is similar but not the same, so when doing assembly it is very difficult to identify where a sequence comes from.”
The fact such a strange genetic phenomenon occurs in one of our oldest crops is no coincidence.
The wheat genome is five times the size of our own, including sequences for traits such as frost or drought tolerance. Breeding that has increased expression of the sections most suited to specific environments is what has made wheat such a widespread food
Co-author Dr Josquin Tibbits of Australia's AgriBio told IFLScience having multiple sets of parallel chromosomes, known as polyploidy, appears associated with larger grains and seeds. The attractiveness of polyploid plants to our ancestors has given us genetic oddities such as potatoes, strawberries, and sugar cane.
Polyploid crops tend to undergo reshuffling of their genes with time, often eventually returning to diploid status (paired chromosomes). Tibbets told IFLScience we can see this already underway in wheat. The 7a chromosome he studied has acquired genes trans-located from other chromosomes in recent times. Tibbets' paper on this chromosome sets forth a path to filling the remaining holes in our knowledge of the genome.
