The results of a research project funded by the Government of Canada's Genomics Research and Development Initiative (GRDI) will deliver almost immediate benefits to Canadian wheat breeders while setting the stage for even more dramatic improvement in wheat breeding over the longer term.
As project leader Dr. Sateesh Kagale explains, "There is tremendous potential for crop improvement through the modulation of meiotic recombination—that is, enhancing the mixing of genetic material that occurs when different varieties of wheat are crossed with one another."
To that end, Dr. Kagale and his team at the National Research Council of Canada (NRC) Aquatic and Crop Development Research Centre in Saskatoon have developed a so-called gene expression catalogue for meiosis in wheat. They have identified, for the first time, the range of genes that are expressed at the different stages of meiotic recombination in wheat.
An essential beginning…
At the University of Saskatchewan, professor and wheat breeder Dr. Curtis Pozniak says that, given wheat's very complex genome, identifying which genes are involved in deciding how recombination happens is a real achievement.
"With this gene expression catalogue, Dr. Kagale and his team have taken the essential first step toward enabling meiotic modulation in wheat," says Dr. Pozniak. "Knowing which genes are involved in recombination, we can start working on understanding what each of them does and finally, figuring out ways to manage when and whether those genes are expressed in order to increase or decrease recombination, depending on what the breeder is trying to achieve."
…and a breakthrough
Agriculture and Agri-Food Canada (AAFC) Research Scientist Dr. Kevin Rozwadowski, a specialist in recombination biology, says, "The results of this GRDI research led by Dr. Kagale will stand as a landmark in the field of plant meiosis. This gene expression catalogue really is orders of magnitude beyond what has been achieved up to this point."
In fact, in what Dr. Rozwadowski calls "a real breakthrough for Canadian breeders," Dr. Kagale and his team have already developed a real-world example of meiotic modulation. This advance will support efforts to achieve a much-needed increase in genetic diversity in commercial wheat varieties.
Going wild: the Ph1 deletion
As Dr. Kagale explains, while wheat's wild ancestors are a promising source of novel genetic material, after centuries of domestication, modern wheat no longer recognizes its wild relatives, making it difficult to cross the two without elaborate manipulation in the lab.
"It has been known for some time that, during recombination, one or more genes at the Ph1 locus on the wheat genome act as a kind of genetic barrier to what it sees as alien DNA," says Dr. Kagale. "While there is a line of Chinese Spring wheat from which the Ph1 locus has been deleted, this cultivar is very different from the wheat we grow in Canada. It would take years of back-crossing for it to be of any use in breeding programs here. We wanted to develop our own Ph1 deletion."
Using gamma radiation, Dr. Kagale's team irradiated 3,000 seeds from an elite Canadian variety called CDC Stanley, germinated them, and then sequenced the DNA of the growing plants to see if the Ph1 locus was still there. "You can't target a specific spot on the genome with the radiation, so it's really a random process," says Dr. Kagale. "You're just hoping that in at least some of the seeds, you'll have deleted the Ph1 locus without deleting other, important parts of the DNA."
A boon to Canadian wheat breeders
In the end, the researchers found about 20 plants with the deletion they wanted and used these to develop a line of CDC Stanley with the Ph1 deletion that can be used for breeding purposes.
"Having a Ph1-deletion variety that's compatible with Canadian breeding programs is going to have a real impact in the short term," says Dr. Rozwadowski. "It will be easier for breeders to introduce genetic material from wheat's ancestors, increasing genetic diversity and potentially, additional genetic resistance to important diseases such as fusarium head blight."
Perhaps not surprisingly, Dr. Kagale is already getting requests for seeds from the CDC Stanley Ph1 deletion line from breeders and wheat geneticists in Canada and elsewhere.