b"The Buzz onDiploid PotatoesWhat are diploid potatoes and why are breeders and processors so interested in them?BY: ASHLEY ROBINSONDIPLOID POTATO BREEDING, and producingla crme, many of those plants look absolutely varieties from true potato seed, has beenhorrible. Because they are, they have revealed getting a lot of attention in the potato industrythe deleterious allelesthe deleterious parts ofhowever growers wont see these new potatoesthe genetic constitution of tetraploid potato that in their fields for a while. The potato industry iswe've been carrying along for as long as we've working to explain what this new technology isbeen breeding potatoes. When we see plants that and why growers should be interested. A panelare weak, that look terrible, that's actually a fine discussion about it took place at the virtual Potatothing, because we can just throw those away. Expo on Jan. 6, 2021. Spud Smart listened in toAnd we keep the strong ones, the ones that look get the 411 from Paul Bethke, a plant physiologistbetter. We select for, just in this one step, we with the United States Department of Agriculture,start selecting for favourable genetic traits and Jeremy Singer, director of agronomy for J.R.while we're removing unfavourable traits, Simplot Company. Bethke explains.HOW DIPLOID POTATOES DIFFER FROMHOW DIPLOID BREEDING TETRAPLOID BRED POTATOES CAN HELP TO MAKE BETTER Current cultivated potatoes are tetraploids.POTATOESThey have four copies of every genediploidFirst goal is capture the good, discard potatoes have two copies. Doesn't seem like muchthe bad. The second goal is to try and fix of a difference, but actually, it makes things sosome of the key traits. And finally, we start much simpler when you're doing breeding. Anddoing inbreeding to make uniform lines that can when you're trying to understand the genetics ofthen be crossed to produce hybrids. important traits, traits that matter to growers, toMany of you are getting garden catalogues processors to consumers, Bethke says. this time of year. If you see F1 hybrid, this is what maybe we're talking about. You create two lines HOW A DIPLOID POTATO IS CREATEDthat are true breeding, you cross them together, FROM A TETRAPLOID POTATO and every one of their progeny is essentially the We can just do it by crossing to a special classsame. And there's an advantage here because ifof many of the pathogens causing diseases that of pollinators that when you cross, put the pollenwe make small changes to either of those parents,plague our industry.onto the flower of your tetraploid variety, yourwe can change the progeny by adding those smallThere are greater than 150 diseases in po-favourite variety, you create offspring that arechanges, which is to say we can improve antatoes globally, of these about 40, which are eco-based only on the female, only on your tetraploidexisting variety, Bethke says. nomically important. And in just the last 40 years, varieties. They are fatherless plants. So, youseven new pathogens or pathogen genotypes have create using this genetic trick, you could createTHE POSITIVES OF USING DIPLOIDbeen introduced into the U.S. On average, the po-diploid plants from tetraploid. And when you doBREEDING tato industry faces a new pathogen about every six that, some really interesting things show up. Developing a true potato seed is very excitingyears, and we believe diploid breeding will allow Many of those plants, even though they camebecause in true seed crops, less than five perus to breed varieties that can help to reduce the from one of your most beautiful, cultivated potato,cent of pathogens are seed borne. This means weimpact of new diseases and true potato seed will even though they are derived from the crme decan significantly reduce seed borne transmissionreduce disease transmission, Singer explains. WINTER 2021 SPUDSMART.COM 35"