An ongoing search: Research drives industry advances
Cultivar research drives innovation in the potato industry and helps growers find new varieties that address ever-changing crop and industry needs.
Spudman spoke with scientists at two leading research universities to learn about recent discoveries, past disappointments and the sustaining motivation behind perpetual testing and trials.
Revolutionary resistance: Q&A with Alexander Karasev
Research led by Alexander Karasev, potato virologist at the University of Idaho, has found complete immunity to Potato Virus Y (PVY) strains in Payette Russet. Testing is underway on Castle Russet, which contains the same R gene that confers resistance in Payette.
The two varieties have not been widely used since the Tri-State Potato Research and Breeding Program released them a few years ago, as Payette can be slow to emerge from dormancy while Castle is prone to a tuber defect known as hollow heart.
However, both varieties have been touted for strong PVY resistance. Karasev hopes the study’s findings, published in March in the American Journal of Potato Research, lead to broad use of the cultivars as parents within breeding programs seeking to overcome the persistent and expensive threat of PVY.
Tell us about the genesis of the project.
Alexander Karasev (AK): It all starts with the breeding efforts. Types of resistance that exist in potato cultivars to Potato Virus Y are typically represented by two types of genes: M genes and R genes. M genes are very common in commercial cultivars, but this type of resistance is strain specific. Only certain strains of the virus are restricted in infected plants. M genes are also sensitive to environmental conditions, especially to temperature. Breeders don’t really like M genes.
R genes have very broad specificity and are not dependent on temperature. The problem with R genes is that very few commercially attractive cultivars have this type of gene. Initially, they were identified in wild relatives of potato and transferred into the gene pool of regular potato.
Now, breeders are trying to introduce these R genes into commercial cultivars. Payette Russet and Castle Russet are the first examples of cultivars carrying this R gene.
When you’re a breeder, you don’t have that many kinds of strains in your hands. So we volunteer to help breeders because we have a very large collection of PVY strains in our research greenhouse. We set out to prove that these R genes that are available in Payette Russet and Castle Russet are indeed broadly specific genes, providing complete immunity to the virus.
How did the research, which started in 2018, proceed?
AK: We took Payette Russet and inoculated it with 18 different isolates of PVY that we have in our collection, representing 13 different strains. We observed these inoculated plants, looking separately for inoculated leaves and also for spread of systemic infection. We also had a set of control cultivars of potato where we don’t have this R gene present. What we saw was that Payette Russet was indeed completely resistant to all 13 different strains of PVY.
What are the ramifications for the potato industry?
AK: Payette Russet can be used very confidently as a parent for producing different kinds of potato cultivars, different varieties for processing — for chips, for french fries, for fresh market — anything. You can introduce it to any potentially attractive cultivar and be sure that it will produce resistance to all strains of Potato Virus Y.
It’s a long way until these R genes can be introduced into a large number of commercial cultivars. But still, this genetic resistance is the most economically viable method of control. It is also environmentally friendly, so you don’t have to use any chemicals. If you have resistance in your cultivar, it takes care of all the problems with minimum inputs.
Educational journey: Q&A with Mark Pavek
Mark Pavek’s 20 years as a Washington State University professor and potato specialist have been marked by highs and lows — including a valuable lesson learned early in his career.
Since joining the faculty at WSU, where he received his doctorate in horticulture in 2004, Pavek has overseen the release of 32 potato varieties in conjunction with the USDA’s Agricultural Research Services Northwest Potato Variety Development Program.
What are the main characteristics you look for in a new variety?
Mark Pavek (MP): I’m looking for varieties that will suit our growers best and always looking to improve their production and their livelihood. We know what the problems are, and we go after the big ones.
Let’s say Potato Virus Y. That’s a big problem, especially for seed certification and for production. The breeders will target varieties that have natural resistance (and) they try to breed those into a modern cultivar. The problem they (breeders) often come up with is that the varieties that have resistance maybe have a round tuber and it may be small. It may not produce a lot of potatoes. So they’re trying to match that with some other cultivars that we use now or might use in the future to get the size, yield and quality right for whatever market we’re targeting. That’s kind of where it starts.
How does varietal development research, done in partnership with the Tri-State (Idaho, Oregon and Washington) Potato Research and Breeding Program, work?
MP: We look at about a quarter million (of new varieties) each year across the states. In the first year in the field, we’re looking for eye appeal. We’re looking for yield, the shape. If it’s going for processing (87% of our market), it doesn’t have to be that nice. After that first year, we start to do smaller trials looking at controlled yield, where we do replicated plots and we look at them against the controls.
We’re looking for aspects that will make them better potatoes than what we already have. And there’s a lot of them: yield quality, storability, disease resistance. Maybe it tolerates heat better, maybe it tolerates drought better. Especially now, that’s important.
It can take 12-plus years to come out with a variety to the public, and then once you release the variety, the seed growers have to have time to ramp up the seed.
Do you learn something at every stage?
MP: Most varieties look good at the initial stage and then they slowly drop out over time because we start refining the research and looking at all the other parameters. We’re looking at disease resistance right away.
As we move through the trials, we start looking at yields. As we get closer to advanced trials, then we start looking more at bruising, potato quality, how well do they french fry if they’re going for processing, do they store well, can growers grow them without having major issues, that kind of thing.
Most of them get thrown away. When we release a variety, we’ve sent it through processors or had fresh-packed people look at them. If there’s strong hope, then we’ll release the variety. A lot of times, we get our hopes up and we get a variety out there and the industry goes through its paces, and one thing or another … there’s just something that happens that maybe we didn’t see.
Is there an experience with a variety that stands out to you?
MP: Back in the early 2000s, Premier Russet came out and looked really good because it actually had Potato Virus Y resistance. It had good yield, french fried well in all of our trials, processors were interested in it. When we released it, everybody started growing it as seed and then the growers wanted to grow it.
But over the course of a few years, McDonald’s, through their testing, found that something about the starch grain — this is what I heard through the grapevine — wasn’t right. When McDonald’s says no, that’s pretty much the end of a processing variety. A lot of people lost a lot of money on that one, because initial reports were wrong.
We’ve seen that happen over the years, so I think as we go through this process, we’re a little bit more cautious than we used to be.
Are there any promising varieties on the horizon?
MP: There’s one that’s out there right now that I really like: Mountain Gem Russet. It may bruise a little more than (varieties) that are out there for fresh pack, but the advantage is, the yield is huge.
If people are trying to look for efficient varieties that do well with less water, less input, this Mountain Gem Russet is one of those potatoes. We did a taste panel testing back in 2018, and it was the best-tasting Russet potato out of all the standards that we look at, (but) taste is one of many components to get a potato to market.
There is a new purple potato that we’re looking at. Although the market is small for those, it’s a really pretty potato. We call them numbered clones until we put a name on them.
How is a variety named?
MP: Clearwater Russet, we got the name from the Clearwater River near Central Idaho. Umatilla Russet was named after the Umatilla, Oregon, location. A lot of times the breeders will just throw something out there, like Castle Russet. One potato was named Rainier Russet after the mountain. One was released not too long ago named Defender, which had great blight resistance.
What keeps you motivated to find new varieties?
MP: Out of all the things I do and anybody does research-wise, the one thing that I think has the best hope to keep potato farming profitable and sustainable and keep growers in business is new variety development. These new varieties are a quicker way to get potatoes that will handle heat, stress, drought. It’s the quickest route to get a bigger yield. It’s the quickest route to get better quality, better storability, better bruise and disease resistance. That’s why we’re so focused and spend so much money on new varieties. It’s just the best way to get there.
