Dr. Bourlaye Fofana and his team’s discovery of common scab resistance genes in diploid potatoes is an important first step in the potato variety breeding process. (Submitted photo/Agriculture and Agri-Food Canada)

By Alice McFarlane

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Diploid potatoes are quickly becoming noteworthy spuds for breeding new commercial potato varieties.

Wild diploid potatoes have two copies of each chromosome in their DNA, unlike more traditional tetraploid potatoes, like Russet Burbank, which have four copies of each chromosome. Fewer chromosomes make diploid genetics easier to work with for breeders.

First domesticated in the Andes of South America, diploid potatoes are often a little smaller in size than their tetraploid cousins. Their untapped genetic potential is being harnessed by geneticists and breeders to develop new diploid potato varieties for farmers.

Agriculture and Agri-Food Canada (AAFC) research scientist Dr. Bourlaye Fofana is leading the pre-breeding charge for diploid potatoes.

“There is more natural genetic diversity in wild diploid potatoes compared to tetraploids that make them interesting for breeding. First, we created more diversity on top of what they have naturally by inducing a change in their genetic make-up. Those changes are random, however, and we don’t know the full picture until further research is done.”

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After successfully pinpointing drought resistant and early maturing genes in diploid potatoes, he’s moved onto to his next foe — common scab disease.

Common scab is a widespread issue that can lead to major economic losses for producers across Canada. Lost profits from waste occur when more than five per cent of a potato is affected by unsightly common scab, which means they cannot be sold to the fresh vegetable market.

Also, the lesions make potatoes difficult to peel, resulting in waste and lost profits in the chip and fry markets. Common scab resistant potato varieties are scarce, so developing potato varieties with resistance is vital for industry.

In order to find common scab resistance for diploid potatoes, Fofana dipped into his collection of diploid germplasm — the seeds, plants, or plant parts used in crop breeding — research, and conservation efforts.

The seeds were planted at the AAFC Harrington Research Farm and once harvested, were evaluated for various common scab resistant traits including the percentage of the surface area of the potato covered by common scab.

The team found genetic markers on the diploid chromosomes for common scab resistance. Of the 384 diploid clones, the group identified 61 that are tolerant or resistant to common scab disease and have genes that help the potato plants to defend and protect themselves against diseases. These 61 varieties will now be evaluated for yield and quality in larger commercial field plots.

“The commercial plots are more comparable to what a commercial farmer might see on their fields. We want to see how the common scab resistance of the diploid varieties translates from the research field plots to commercial field plots,” Fofansa said. “This gets us another step closer to commercial diploid potato varieties.”

The 61 varieties will now be evaluated further for yield and quality as well as tested in larger commercial field plots to see how they perform in settings similar to farms.

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alice.mcfarlane@pattisonmedia.com

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