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Essence of a potato

July 19, 2011

In a DW interview, a Dutch scientist explains the importance of DNA sequencing for potato breeding. He was part of a 14-nation group of experts which has published the genome of the tuber crop potato.

Potatoes are one of the world's most important cropsImage: BilderBox

The potato is the world's second largest staple crop, behind rice. Researchers from around the globe are working on sequencing various food products so that they can be bred or engineered to be more nutritious in the future, or can grow better in suboptimal climates.

Deutsche Welle spoke with Richard Visser, a plant biologist at Wageningen University and Research Centre in the Netherlands, who participated in the consortium which published the first genetic sequence of a potato in the journal, Nature, earlier this month.

Deutsche Welle: Your paper is entitled "Genome sequence and analysis of the tuber crop potato." What does that mean exactly?

Richard Visser: What we tried to do is to elucidate the DNA sequence order of the potato. In modern genetics, and modern breeding, we are now in a phase where if we have DNA sequence information, we can much more easily devise markers and identify the genes which are important in certain traits. For every chromosome in the potato - the potato we grow in our fields has 12 chromosomes - it's a tetraploid, meaning that there are four pairs of chromosomes, and from every chromosome we try to elucidate the order of the base pairs that are in the DNA: A, C, T, G.

Richard Visser
Richard Visser says that the sequencing will significantly speed up breeding timesImage: RGF Visser

Isn't there more than one basic type of potato?

Yes, that's correct. Although it says "the potato," what we actually did was sequence "a potato." In this case, we sequenced a particular type of potato because it has four different genomes in one plant and that makes it difficult to sequence, so we went down to a simpler version of the potato - in diploid form, so only two genomes. We have sequenced this potato genome.

You can compare it to a book, and of this book, we know the different chapters, and we know on the different pages what is written, more or less, but there are mistakes or we cannot read. That means if you have a different kind of potato, the words may be a bit different, and may have a different meaning, but also perhaps a synonymous meaning.

There are scientists from all over the world who are part of this potato research group. Were a lot of you working on this simultaneously, or was it intended to be an international project from the beginning?

It was intended to be an international effort from the beginning. When we started about five or six years ago, the sequencing costs were, at that time, very high. There was only one method of sequencing at that time, and it was very expensive. So my idea was that if we can collaborate by trying to sequence the potato genome, then maybe we can do that.

Potato queen
Potatoes are strongly associated with German cuisineImage: AP

So that's why we tried to get together people from all the major potato-growing countries - or culturally important countries for the potato - to get involved. And they had to organize their own money, and then each one would sequence one of the 12 chromosomes, and if we had 12 partners then, in principle, we would have the sequence of the potato in a few years. However, a few years ago, the technology for sequencing became much cheaper, which has allowed us to finish the sequencing much faster than we had thought in the beginning.

What do you expect potato growers to be able to do now that you have sequenced this?

Of course, it takes time for scientific findings to drizzle through to the breeders, but in principle - and this is being done by Dutch breeders, as far as I know, and I don't know about other countries - is that they indeed use the sequence information to design markers for specific traits. The potato is a very interesting crop, but the breeding is quite difficult. That means that for many traits, you have to wait four or five years.

French fries
There are plenty of ways to cook a potatoImage: BilderBox

After you have made a cross, you have seeds, and then the breeders select the best plants from the hundred thousand from which they start and in year four or five they have 200 seeds left and they can make sufficient tubers for all kinds of tests. So they have to wait four or five years, and select plants every time which they throw away afterwards. If they have markers, then you can select for particular traits you're interested in already in the first year, in 100,000 plants. And you can throw away the rest.

So that speeds up this process?

Yes. And so you can only work with plants that you know have some of the traits that are really important.

How do you think this research will impact food security and world hunger? What long-term impact might it have for the developing world?

The long term impact might be that we can breed more efficiently for potato plants which also under less favorable conditions (less water and fertilizer, droughts, etc) will give a good and predictable yield. If yield stability is a fact then it means that yields will be more stable and thus food production will be secured.

So because you do work in potatoes, are you an expert in cooking potatoes too?

No, not so much. I can cook potatoes, but I follow the instructions on the plastic bag. Hard-boiling, soft-boiling, or whatever. I'm not a master chef.

Interview: Cyrus Farivar
Editor: Kate Bowen