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Gene library opens new doors for potato research

Date posted: February 5, 2002

Technology advances are freeing up a wealth of genetic resources to make unprecedented advances in sustainable crop production. Case in point is a study at the Lethbridge Research Centre.

When Dr. Qin Chen began mining a wild Mexican potato species for valuable genetics less than two years ago, little did he expect to strike gold so soon. But that’s exactly what the Lethbridge Research Centre scientist has done, using an innovative DNA library that represents dramatic new potential in crop genetics research.

Using this resource to probe the genetics of a wild Mexican potato species, Solanum pinnatisectum, Chen and colleagues identified high levels of resistance to late blight disease and the Colorado potato beetle, the number one disease and insect problems of potatoes worldwide. These problems cost Western Canada’s potato industry a combined estimate of roughly $20-25 million annually for fungicide and insecticide control.

“This is a treasure - we’re extremely fortunate to find high levels of resistance to both problems in one species,” says Chen, a molecular cytogeneticist. “This is the first step toward transferring this combined resistance into a high-quality potato cultivar for Canadian producers.”

Step two is already well underway, he says. Chen and colleagues have examined the wild species to identify the nature of both resistances, as a basis for innovative strategies to isolate and transfer the desired genetics into potential new potato varieties.

This progress means significantly more than direct economic benefits, says Chen. Western Canada’s potato industry has expanded significantly in recent years, a trend that has drawn concern because of the high levels of inputs used in production. Developing more sustainable options is a top priority of the Lethbridge Research Centre and the entire Agriculture and Agri-Food Canada potato research network.

DNA technology drives success

This success story is largely the result of the DNA library – specifically, a powerful genetic resource called a bacterial artificial chromosome (BAC) library, says Chen. A BAC is a special vector used for cloning large pieces of DNA. Using BAC vectors, Chen and colleagues developed a library that represents the complete genome of Solanum pinnatisectum, the wild Mexican potato species that yielded the two-for-one resistance.

Solanum pinnatisectum is of great interest to scientists because it is resistant to several insects and diseases that plague Canadian potato crops, says Chen, who led development of the BAC library in collaboration with scientists from Texas A&M University.

“The challenge is that despite their value, resistance genes in wild species come loaded with undesirable traits that would take years of painstaking work to remove through conventional breeding,” he says. “With this BAC library, we now have a tool to help us identify the important genes and work more efficiently to incorporate them into the breeding program.”

Large-scale benefits

The advantage of larger BAC libraries over traditional DNA libraries, is that they allow researchers to perform large scale potato genomics research, and to study an entire gene, rather than just pieces of genes. “Since many agronomically important traits such as disease resistance and quality are often controlled by a large gene or multiple genes, using the BAC vector is a much better way to construct a DNA library,” says Chen.

Even with the technology advances, pinning down valuable genetics remains a formidable challenge, he says. But the process is far more streamlined with the BAC library. “The entire potato genome has about 30,000 genes. In order to ‘find’ the genes we’re looking for, we need to identify the molecular markers that are closely linked with the traits we’re after. We can then use those markers to screen our BAC library to find which clone is carrying the trait.”

The Lethbridge work is one piece in an international researcher effort to sequence the entire potato genome, says Chen. “Just as the human genome project will be a boon for medical science, the gene sequence of the potato will tell us which parts of DNA have what kind of function, and that will dramatically boost the efforts of breeders in developing high quality, disease resistant potato cultivars for western Canadian producers.”