Hybrid potatoe breeding is the future for KWS Saat

Most varieties of sugar beet will continue to be used for another few years, and will then make way for new, better-performing varieties. The German crop breeder KWS Saat believes this may soon be the case for potatoes too, and it ultimately hopes to breed hybrid diploid potatoes from seed. That may still take at least 10 years to achieve, says Executive Board member Peter Hofmann, though he points out that “KWS invests for the long term”.

KWS Saat focuses solely on hybrid potato breeding

In 2016, KWS sold its traditional potato breeding business, and since then it has been focusing solely on hybrid breeding. “KWS wants to expand, and that is not easily possible in the traditional potato breeding sector,” says Hofmann. “That market is already saturated. We have identified opportunities in the hybrid breeding of diploid potatoes, which is a completely new technology for this crop.”

A member of KWS personnel uses an electric toothbrush to shake off pollen from the stamen of a potato plant. The pollen will be used later for cross-fertilisation. – Photo: Ruud Ploeg

4 sets of chromosomes, or 2

The new approach is two-fold: hybrid breeding is a well-established technology for sugar beet, oilseed rape, maize, sunflowers and grain, but it is novel when it comes to potatoes. The other aspect is that KWS is breeding diploid potatoes rather than tetraploid. Practically all cultivated potatoes are tetraploid, with 4 sets of chromosomes. In contrast to the benefit of higher yields, the disadvantage is that cross-breeding gives rise to wide variation in the progeny, making it difficult to breed in the desired characteristics or improve existing ones.

This disadvantage is eliminated in diploid potatoes, which have two sets of chromosomes; they are generally weaker, however. “We have removed a major obstacle,” explains Hofmann, “and we can now breed diploid potatoes with wide genetic variation, which makes selection, and therefore improvement, possible. In our field tests, the diploid potatoes are already at 80% of the level of tetraploids, on average. The best diploid potatoes are even already achieving the same results as the tetraploids. It looks promising.”

Greater interest in diploids Solynta also focuses on the breeding of hybrid diploid potatoes. It has announced that it has successfully bred double resistance to Phytophthora diseases into diploid potatoes. Pim Lindhout, head of R&D, explains: “Hybrids have two parents. By breeding a different type of resistance into each parent, and then crossbreeding these resistant parents, we now have hybrids with two Phytophthora-resistant genes.” Solynta already planted diploid potatoes last year. The harvest will be used as seed potato stock in 2018. – Photo: Anton Dingemanse The potatoes are not yet ready for commercial market launch. “Our breeding programme with homozygous diploid parent lines will enable us within two years to also breed in other commercially useful characteristics, without losing the resistance to Phytophthora. We will then still have to apply for plant breeders’ rights. We expect to be able to launch a commercially useful potato variety with long-term Phytophthora-resistance onto the market by 2021.”

More efficient breeding process

In hybrid breeding, you crossbreed separate father and mother lines with a limited genetic variation. As a result of the heterosis effect, the progenies are better than both parents, and hybrid breeding enables you to achieve combinations of crossbreeding in a more targeted way. By using diploid potatoes, the breeding process becomes more efficient. The genes for new or improved characteristics only need to appear on 2 pairs of chromosomes instead of 4. The transition to hybrid diploid varieties of sugar beet took over 20 years, but KWS believes that this will be possible for potatoes within 10 years.

Potato seed

The ultimate aim is to grow potatoes from seed, states Hofmann. “Seed is far less susceptible to disease than tubers, plus it is easier to store and to transport. We are also breeding our diploid potatoes to have characteristics that will make it possible to grow them from seed. That could result in far more plants per hectare, growing one or two tubers from a single seed, and that shortens the growing season.”

Once cross-fertilised or self-fertilised, the plant develops berries. Bags are positioned to prevent them falling onto the floor. Each bag has a number to enable the plant to be identified. – Photo: Ruud Ploeg

“The question is also whether you still need to grow potatoes from seed in ridges, or simply grow them in the ground as with sugar beet. It could turn out, however, that in our temperate climate it takes too long to achieve a sizeable yield directly from seed.”

In the future, we may see a system in which basic potato seed is cultivated in the warm regions of southern Europe. Or we may grow young plants from seed in greenhouses, which we then plant out in the field, as we do with oilseed rape in north western Europe. Growers also do this with sugar beet in northern Japan, where the growing season is too short to grow sugar beet from seed.

Greater clarity after 10 years

It would mean a significant change for the potato sector. “Traditional breeding will continue for the time being alongside the new breeding methods such as that used by KWS,” remarks Hofmann. “It will certainly take another 10 years or so before it becomes clear what the outcome will be for breeding and cultivation.”

KWS – a largely family-owned company KWS Saat is an international breeding company with its headquarters in Einbeck, Germany. KWS is 56%-owned by the German Büchting and Arend Oetker families, while 15.1% is owned by the investment company Tessner Beteiligung. The remaining shares (28.9%) are listed on the Frankfurt Stock Exchange. Its turnover in 2015/2016 was € 1,037 billion, of which 17.6% was spent on research and development. The potato breeding business of KWS is located in Nagele in the Netherlands. – Photo: Ruud Ploeg KWS Saat is concerned with breeding maize, sugar beet, grain, oilseed rape and sunflower, in particular. It has been breeding potatoes since 1920 via its subsidiary Ragis. In 1987, Ragis began a collaboration with the German company Saka. This came to an end in 2007, and KWS lost a major foothold in the international seed potato market. For this reason, it began a partnership with Dutch seed potato firm Van Rijn in 2008. In 2011, KWS became the full owner of the joint venture and founded KWS Potato. In 2016, KWS sold its traditional breeding business to Stet Holland, and since then has only been concentrating on hybrid breeding.