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How gene-mining wheat’s wild ancestors could improve our modern crops

Wheat has been with us for a long time. Exactly how long we may never know, given that soft plant matter, unlike stone, pottery and bone, tends not to be well preserved in the archaeological record. The Ohalo II site in Israel is a bit of anomaly in this regard, owing to its submersion by the Sea of Galilea shortly after the settlement was deserted.

It’s at this Paleolithic site, some 23,000 years old, that the first evidence of collected wild emmer wheat, Triticum turgidum, was unearthed – a discovery that also provides the first indication of a people who may have intentionally disturbed the land in order to facilitate its growth. If validated, it’s a finding that would unwind plant cultivation, if not domestication by 11,000 years.

The majority of our current bread wheat varietals are descendants of those wild emmer grains. Our Neolithic ancestors, who first began to farm wheat, began the process of selecting for desired traits, many of which, such as threshability and size, remain important today.

A good deal of genomic analysis has been conducted on wild emmer wheat. Some has traced genes that had gradually been lost, such as NAM-B1, which is linked to rapid maturation and was found in Nordic wheat varietals as recently as 140 years ago, and is now being re-introduced.

This month, a team at the University of Kansas announced a genetic study of a wild and distant relative of bread wheat that has resulted in a model to improve genetic mining of wild wheat varieties for resources that may be transferred to bread wheat cultivars in order to improve characteristics.

Using next-generation sequencing technology in combination with flow cytometry, the team studied a single chromosome, 5M, from Aegilops geniculate, a very distant wheat relative (so removed, it’s considered a grass) in order to come up with their strategy.

As an example of the potential impact from the gene-mining model, the study’s first author, Vijay Tiwari, pointed to three particular genes in Aegilops geniculate that have evolved to confer resistance to wheat rust, a pathogen that has devastated wheat crops since Roman times.

Analyzing these ancient specimens may one day tell us a great deal about the evolution of today’s most widespread food crop, including, perhaps, how it has adapted to withstand environmental and human impacts.

Successfully transferring the best of these genetic traits may also improve our modern-day cultivars. But first, we need to better understand the genetic makeup of what we currently grow.

In June, I reported on progress in sequencing the multi-faceted wheat genome. More recently, it was announced that Canada would begin to generate a high quality reference sequence of wheat chromosome 2B, complementing other work being conducted under the International Wheat Genome Sequencing Consortium (IWGSC). Of the 21 wheat chromosomes, only one (chromosome 3B) has been sequenced to high quality, with work underway in 12 countries, including Canada, to complete reference sequencing for 13 additional chromosomes over the next two years.

The Canadian arm of this project will be led by Dr. Curtis Pozniak of the University of Saskatchewan, in collaboration with Dr. Andrew Sharpe of the National Research Council Canada, and is funded by Genome Canada and the Western Grains Research Foundation.

Chromosome 2B has previously been identified to have genes important to pest resistance and drought tolerance, and it is expected that the eventual findings will lead to higher yields and better drought and disease resistances.

How gene-mining wheat’s wild ancestors could improve our modern crops

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