Good things come from our wild cousins

Perhaps the most devastating pest in the potato farming business is the Colorado potato beetle, which causes significant crop damage and is notorious for quickly developing resistance to chemical insecticides.  |  Peggy Greb/USDA photo

Spuds comprise more than one third of all vegetables Canadians consume annually. That’s $1 billion worth of spuds every year. Canadians gobble up 157 pounds of potatoes per person per year.

In contrast, our skinny American neighbours eat only 128 lb. of potatoes per year.

With a long list of natural enemies, potatoes are not easy to grow. Disease and insect invasions force growers to spray crop protection products up to 20 times in one growing season. That’s a practice the potato-eating public does not like.

Perhaps the most devastating pest is the Colorado potato beetle, which causes significant crop damage and is notorious for quickly developing resistance to chemical insecticides. Researchers in all potato-eating countries are working to find non-chemical methods to control or eliminate the Colorado potato beetle.

There is reason for hope. Some wild relatives of domesticated potatoes have natural defences against these beetles. Researcher Natalie Kaiser has been looking at isolating and adopting some of these natural beetle-killing compounds for domestic use.

“Some of these compounds can kill Colorado potato beetle larvae. These compounds also dramatically reduce adult beetle feeding.

“But consuming large amounts of these natural compounds can have adverse health effects in humans. While beetles chomp on potato leaves, humans obviously do not. So, it’s desirable to create potato varieties that produce anti-beetle compounds only in their leaves,” said the Michigan State University scientist and lead author of a recently published study on the concept.

Kaiser said generating this beetle-resistant variety of potato has been a challenge. One hurdle is testing potato varieties for beetle resistance. Field trials can take months if not years. They are costly and resource intensive. Kaiser and colleagues developed a research shortcut. They compare the chemical profile of hundreds of individual potatoes with their real-world in-field resistance to the beetle.

“We found chemical signatures that could predict resistance to Colorado potato beetles. Breeders can select resistant potatoes with a simple chemical measurement instead of having to conduct field trials. This method could save time and money.”

Another obstacle in breeding beetle-resistant potatoes is the sheer amount of genetic information breeders need. There are several genes controlling the types and amounts of anti-beetle compounds any given potato variety will produce. It’s challenging to track all those genes during breeding. And breeders must keep in mind other traits like yield and tuber appearance.

“There are approximately 40 important traits to consider when developing a new potato variety. Assembling the right combination of genes controlling all these traits is crucial.”

The process is complicated by the fact that potato varieties often have four copies of every gene. Potato isn’t the only crop to have multiple gene copies, known as polyploidy. Having four copies of each gene makes potato genetics complicated. Each of the four copies can be a different version of the gene.

One way around the quadruple-copy problem is to only use potato varieties that naturally have just two copies of each gene. Like most animals, Humans have two copies of every gene, one each from male and female parents. This is called diploid.

“But many diploid potato varieties are self-incompatible. This means a plant will not set fruit and seed when a flower is pollinated with its own pollen. This reproductive barrier makes breeding very challenging.”

Kaiser and her team developed diploid potatoes that are self-compatible. Through this process Kaiser and her team discovered that multiple genes and the environment determine whether some potatoes can produce self-fruit and seed.

They worked with key genetic resources called recombinant inbred lines to aid in breeding new potato varieties. These lines are created by inbreeding two or more plants until they are all genetically identical and share the same traits.

“The new potato varieties and genetic tools will allow researchers to examine the genetic foundations of self-fertility, and insect and disease resistance. We can create new potato varieties that were previously infeasible.”

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