RE SEARCH New breeding method leads surprisingly fast to new varieties characteristics you think are important. When you start breeding the above-mentioned diploid heterozygote progeny, 50 percent will be heterozygote and the other 50 percent homozygote. When you continue breeding, you halve the percentage of heterozygote with each new generation. In the 6th generation, the progeny will be over 95 percent homozygote again. When you start breeding tetraploid potatoes with four different genes on 1 allele, you need many more generations to obtain a high percentage of homozygote progeny. And this example only applies to a single gene. A potato plant has 30,000 genes. This explains why traditional breeding is a very long-term affair. And if you understand this, you’ll be able to understand the basics of what we’e doing.’ ‘Our method has nothing to do with GMO or whatever else. This will produce the same type of potato as from traditional breeding in the end.’ The reverse process ‘Look, what we’re really doing is the reverse process of what I‘ve just shown. We’re using breeding lines that are homozygote.’ Lindhout gets his writing pad out again and shows that from the Aa x Aa crossing only the progeny of AA and aa are selected. You’ll cross those and get the 1st generation (F1) hybrid, he explains. ‘Why are we doing this? The breeding in method is not yet being used in traditional breeding. That’s not possible with potato plants, nor with diploid, because they contain a range of mechanisms that make them incapable of self-fertilisation. This is called incompatibility. Diploid potatoes are naturally self-incompatible. They do make pollen, but are blocked when the pollen ends up on their own pistils. We’re working with plants, though, that are crossed with the Sli gene, a gene that breaks through the natural self-incompatibility, thus enabling 50 percent of homozygote progeny after one generation. For tetraploid potato plants, it takes seven generations to obtain plants that are 50 percent homozygote. Moreover, we saw crossed progeny that were much better than the earlier diploid crossings. The plants had so much growing power that they were almost comparable with the tetraploid plants. These results gave us the determination to continue on this path.’ The first tests ‘At Solynta, we’ve reached the stage where we have a proof-ofprinciple. We’ve now bred a number of generations from which we’ve produced hundreds of crossings and the first prototype hybrids. We don’t have a commercial diploid variety yet, because the material is basically still very primitive. The reason is that there are not yet any commercial varieties of diploid potatoes. Moreover, we’ve had to extract the gene that breaks through the self-compatibility from a wild potato variety. It comes from a source of plants that have tubers the size of rat droppings, which means that it will take quite a while before those tubers are big enough. Our first objective is to get complete, inbred lines, which we don’t expect to be perfect yet. Only then will we start working on test hybrids. I hope to see the first results in 2015. The consumer won’t hear about this, but the farmer will, because he’ll get better varieties. This has nothing to do with GMO or whatever else. This will produce the same type of potato as from traditional breeding in the end. By breeding with a purpose, the plants are just as strong as the present potatoes, but they’ll have extra fine characteristics. We can use those to gear to the demand of the market, including the consumer.’ The Solynta breeding method enables 50 percent of homozygote progeny after one generation. For tetraploid potato plants, it takes seven generations to obtain plants that are 50 percent homozygote. The differences ‘The big difference between traditional breeding and our method is that planting stock is not derived from tubers but from seed. If you use seed potatoes, the multiplication factor is 10, or ten tubers per plant. If you want to provide the entire country with a new variety, you need at least five years of multiplying from minitubers to consumption potatoes. It’s a time-consuming story, also an expensive one, plus you run the risk of losing some of the quality during those five years. This process will be much quicker once we’re able to use seed. Suppose you need hybrid seed of a particular variety. The breeder will then look for a country with a suitable climate for producing seed, Guatemala, for example. At any rate, a place which is free from pathogens. You can then breed and supply planting stock that’s one hundred percent clean. Your seed will be provided with the Clean Seeds status, which already exists for the pro14 Potato World 2012 • number 3 Pagina 13
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