Agricultural Biodiversity Weblog

This is why we love the internets. Because when we say “one to keep an eye on,” what we really mean is, “This seems odd beyond belief”. And fortunately for us, people who really know their stuff are indeed keeping an eye on things. Matthew V Di Leo commented on yesterday’s post, and has given us permission to elevate his comment to a post, which we are doing because it is too long merely to feature.

Calling mutation breeding a “technical revolution,” particularly this implementation of it, appears beyond absurd to me.

I don’t have access (yet) to the full publication that this appears to come from, but from what I can tell they did the following.

1. Took a rice variety that was already well known to have a set of traits (pale green leaves and semi-dwarfism) that were associated with high yields
2. Mutated a huge number of individuals of another elite line that does not have these traits
3. Looked for new mutations that mimic the original trait
4. Identified the mutations associated with the phenotype with resequencing and created MAS markers to allow them to clear out the extra mutations

A couple points:

1. They didn’t discover agronomically valuable genes de novo–they simply identified them within a known variety. This could also be done by genetic mapping approaches or simply by crossing the plants through traditional breeding and selecting for the right phenotype. Their approach probably speeds up the process by a year or two at most, and might be much more expensive.
2. This only worked at all because they had a simple, highly heritable trait that was incredibly easy to measure. This is very rare. Something complex and subtle like yield or salinity resistance ¹ would be incredibly hard or impossible to do with their approach.
3. No matter how you move better genes into your plant, whether by traditional breeding, mutation approaches, or genetic engineering, the total variety development time is rarely much less than 10 years–especially due to the need for multi-year/environment trials.

Thanks again to Matt, who will surely post something more detailed on his own blog.

Thanks to Nigel for pointing us towards the 24 January edition of the BBC radio programme Farming Today, which had a short segment on mutation breeding. It may not be online for long, and may not be available to all, so here’s a transcript of the relevant bit, which Nigel got from Defra.

Anna Hill: It’s been called a technological revolution which will change the way the world’s crops are grown. We find out how genetic mutation works later in the programme.
(Break)
AH: The UK is leading a revolution in the race to breed new plants as quickly as possible. Scientists at the Sainsbury laboratory in Norwich have developed a new technique which could help farmers in Japan where last year’s tsunami flooded land with sea water leaving such high salt levels that few crops could grow.
Well now the researchers have worked out a high speed way to identify the genes which are resistant to growing in salty soil to breed a new variety of rice within two years.
Dr Brande Wulff explained how important this is for the world’s crops.
Dr Brande Wulff (Sainsbury Laboratory, Norwich): Well this is a huge leap forward. Traditionally it would have been a, a marathon of five years or so to do this type of work or possibly even a long distance endurance event of ten years or so. Now we’ve reduced that to a short sprint of one or two years. So it’s, time is in, is the essence in this type of work and so it’s really a huge leap forward.
AH: How does the process work?
BW: It’s extremely simple. In this case with rice you take your favourite cultivar of rice or variety of rice. You then mutate that. When you introduce mutations you introduce bad ones and good ones and that happens randomly and the challenge is then to take those good mutations and anchor them in your favourite variety and get rid of the bad ones. And that’s done by, by crossing the mutant plant back to the parental variety, the non mutated parent, and then in the progeny you select for the ones that have your desired trait. And so you, you can get rid of the bad mutations in this way.
And then you sequence those plants, you put on your DNA goggles which allows you to look at the sequence and then you pinpoint those mutations or genetic variants that confer the new trait that you’re interested in. So genetic variation takes, it, it’s occurring the whole time naturally, but what the scientist does, he speeds that up in the lab using a chemical mutagen or, or something like that.
AH: Which is not GM.
BW: It’s not GM in, in the sense that we’re, we’re not transforming the plant, we’re not introducing a novel DNA from outside of the plant.
AH: Now the work that’s being done at the moment is looking at salt resistance in rice because in Japan the tsunami contaminated soil with a lot of salt. So how long would it be do you think before Japanese farmers would actually see a new variety of rice to plant which is resistant?
BW: It’s perhaps only a matter of a year or so before they can clean up these plants and then bulk up enough seed so that they can distribute it to farmers.
AH: That’s very, very fast isn’t it?
BW: It is indeed, yes.
AH: So could this be applied to other plants then?
BW: Well really the sky is the limit. This technique requires that you have a good genome sequence of the plant that you’re working on, which we have for rice. We don’t have that yet for wheat, but we do have it for a lot of other crops including very important crops like soy bean, cassava, potato, grape, even oranges and, and apples have been sequenced.
AH: Dr Brande Wulff from the Sainsbury Lab and do join us again tomorrow.

Dr Wulff clearly has a way with words. I particularly liked his reference to DNA goggles. And he understands journalists. But I took the liberty of running said words by a friend of mine who used to work on mutation breeding at the IAEA. He was considerably less sanguine.

A healthy dose of skepticism, re. the timeframe of one or two years to get stable mutants — to be introduced into breeding programs — wouldn’t hurt. Salinity tolerance is a very complex multigenic trait; getting all the mutation events — and their interactions — to confer the desired level of tolerance is quite a tall order. The back crosses to clean out the unintended deleterious effects of induced mutations (breaking the linkage drags), even with MABC, takes time also.

One to keep an eye on.