Why GM isn’t the end game


I’ve written a lot in the last couple of weeks about Rothamsted and Take the Flour Back. In my efforts to outline some of the many flaws in the activists logics, I’ve probably come across as extremely pro-GM. Now seems as sensible a time as any to take a step back and explain why, though I am keen that GM research be carried out, I don’t believe that GM alone will save the world from starvation. I’m horrified at the idea of anyone destroying scientific research, but I don’t necessarily see GM as the silver bullet that some people think it is.

Several people have asked the question ‘Why are the Rothamsted scientists using c.v. Cadenza? We don’t grow it commercially in the UK and it’s a Spring Wheat.’ (In the UK we have wet springs and dry summers, so we grow mainly Winter Wheat.) The answer to that is that the kind of technology being used is not simple, and is not possible in many varieties. Cadenza, along with Canon, Florida and Imp, is one of the few varieties where this work is efficient. They serve as models for lots of different research, purely because they are susceptible to being transformed (GM-ed).

Even if we could transform E β-Farnesene into an elite cultivar, farmers wouldn’t be able to just start growing it all over the UK. Scientists would still need to breed it into lots of other varieties. (In which case, why go to the trouble of transforming the gene into a recalcitrant species? You’re still going to have to do the breeding part afterwards). There are a few reasons for this: the first is that doing a ‘clean’ transformation, just involving the individual gene of interest and nothing else, is even harder than what the scientists have already done. It’s far simpler to transform one plant with a cassette of genes, and then breed the plant until only the gene of interest remains.

The second is that it would not be enough to get the gene of interest into one elite cultivar. When driving through East Anglia past fields and fields of wheat it may appear that the countryside is filled with a monoculture. Not true: not all wheat fields are equal. In the same way that we have Royal Gala apples, and Braeburn apples, and Pink Lady apples, in the UK we grow a good twenty different varieties of wheat. For instance, in your bowl of Weetabix this morning you may have had Claire and Scout.

This is partly because of the requirement for different end products: Wheat used for bioethanol needs a high starch content, whereas wheat for bread needs a high protein content. Bread wheat and pasta wheat are even more different (the former has 50% more genes than the latter). We even grow a feed wheat called Savannah that is higher yielding and resistant to lots of diseases. Unfortunately it makes rubbish bread, so we only grow it to feed to cattle. The need for lots of end products creates a need for lots of varieties.

But we also grow lots of varieties because growing only a single variety of anything is dangerous. In 1970 the American maize harvest was devastated an epidemic of Southern Corn Leaf Blight, which took 12% of the harvest: more than $1 billion worth. This wasn’t a new disease that had not been seen before: it was known in the South, but not on this scale, and never as far north as the US Corn Belt.

The reason the disease had such a devastating effect was that all of the corn being grown had the gene that made it susceptible. Until the 1960s, to stop the corn mating with itself, the anthers had been manually cut off. When somebody discovered a male-sterile variety, which made no pollen and therefore saved thousands of hours of man-labour, everybody started growing it. Unfortunately cytoplasmic male-sterility turned out to be linked to susceptibility for blight. Nobody is going to forget that disaster in a hurry, so even if we only wanted to make a single product,we would never be growing a single variety of wheat.

Also, we don’t keep any particular variety for long. There are always more mouths to feed, and not enough fields. In order to keep increasing yields, and stay abreast of new diseases and changing weather conditions new varieties are constantly being bred. Every six years or so each elite cultivar is retired, and replaced by a new one. Doing a few new transformations a year wouldn’t be practical even if it were possible: so again, we’d still need this breeding program.

Wheat yields in the UK – courtesy of Syngenta

So while it may be possible to show using GM technology that a particular gene (like E β-Farnesene) is a really useful thing to have in the wheat crop, it is still necessary to have a traditional breeding programme in order to get it there, because having it in a single variety is just not enough. (The single exception I can think of to this is papaya. There is no natural resistance to Papaya Ringspot Virus in papaya plants, so when the virus devastated the global papaya crop in the 1970s and 1980s. Since then, GM papayas are grown pretty much everywhere, but it’s probably only a matter of time before the virus overcomes this single resistance gene).

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