Sask. researchers help crack pea genome

The initiative will assist breeders in achieving specific breeding priorities, such as boosting pea protein levels

Plant scientists from the University of Saskatchewan have played a role in an international consortium of researchers that has developed a complete genome sequence for the pea (Pisum sativum).

The accomplishment, which includes U of S researchers Tom Warkentin, Kishore Gali and Bunyamin Tar’an, took six years and was reported earlier this month in the scientific journal Nature Genetics.

In a recent interview, Gali said the genome will help plant breeders to identify molecular markers, make more reliable plant selections for breeding programs and shorten the breeding cycle.

“It contributes to more rapid and reliable breeding,” Gali said.

In Canada, the project will assist pea breeders in achieving specific breeding priorities, such as boosting pea protein levels, improving resistance to root rot and other diseases, enhancing standability and possibly improving the quality of proteins that can be extracted from field pea varieties, added Warkentin.

“It’s definitely something that we feel quite excited about, partly because it was a project that involved many people, from many countries, over many years,” he said.

“When a project like this is finally completed, it’s a sense of accomplishment and also relief that it’s done.

“I think it’s also a feather in the cap of Saskatchewan Pulse Growers because they were the main contributor from the Canadian side. Our work relied a lot on their support.”

The pea genome project was led by a group of French scientists but the Canadian research team was involved from the beginning and made critically important contributions.

In addition to identifying strategies and approaches to the sequencing work, the Canadian team — in collaboration with a Dutch company called KeyGene — also developed a “physical map” for peas that laid the groundwork for the detailed genome sequencing work to be completed.

Other groups involved in the project were from Australia, the United States, the Czech Republic and New Zealand.

Warkentin described the pea genome as very large, with nearly 4.5 billion base pairs.

That’s similar in size to the lentil genome, larger than soybeans and corn, nearly five times bigger than canola, but smaller than the wheat genome.

“It’s taken time but it’s a very complex project,” Warkentin said.

“We knew beforehand — but it was confirmed (through the project) — that approximately 85 percent of all the 4.5 billion base pairs are what we call repetitive sequences, so they’re not genes but more like repetitive bits of DNA.

“When you have that much repetitive DNA, it makes it more and more complex to put it all together in a sequence.”

A genome consists of all the DNA of an organism.

A genome sequence identifies all of the DNA of a given organism and assembles it in its proper sequence.

Only a small portion of a pea’s DNA consists of actual genes that contain codes for enzymes, which are important for the development of beneficial plant traits, such as disease and lodging resistance or protein levels.

Warkentin said the pea has 30,000 to 40,000 genes that are scattered or clustered throughout its genome.

Creating markers that help locate those genes will allow breeders to develop improved pea cultivars more quickly and efficiently, resulting in a crop that is more valuable, both economically and nutritionally.

The project sequenced the genome of a French pea variety known as Cameor.

Cameor is not grown commercially in Canada or France but was chosen because it has been the subject of many previous genetic studies conducted in France.

Despite Cameor’s limited commercial production, its genome will be beneficial to pea breeders around the world because it will serve as an initial template or reference genome, something that hasn’t previously existed.

“We have had discussions that maybe in the not too distant future we might like to sequence a recent Canadian cultivar because as I understand it, once you have this initial template, the cost of doing a second sequence is much, much less, both in terms of the complexity and the time required,” Warkentin said.

“By doing that, we might be able to elucidate a few more interesting things that may be a bit more applicable and relevant here, but having said that, I think the sequence of Cameor is still perfectly valuable here.”

Gali said key contributions by the Canadian research team will advance knowledge of pea breeding and enhance the reputation and responsibility of U of S pulse researchers.

Gali, Warkentin and Tar’an are plant breeders at the university’s Crop Development Centre in Saskatoon.

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