One of the claims made every-time you hear a proponent of genetically modified plants talk is that GM plants are required to feed the world because we are facing a global food security crisis. Whilst I would agree we are facing a crisis, is this true? Are they the technological leap forward agriculture has had in the past and can they overcome many of the climate and peak oil issues we face with growing enough food in the future?
There a number of reasons why GM may not be the solution. Some of these are commercial, some how our agricultural system works and some are due to the current scientific limitations of GM technology. Taking each of these points in turn.
Historically GM has aimed at modifications that do not directly benefit the consumer but apparently only the big agro companies or possibly the farmer. In 2002 almost all GM crops in production were modified for herbicide resistance, insect resistance or virus resistance. A few modification traits were in production for improved shelf life (Scragg, Environmental biotechnology 2005). Although I heard on the news in 2012 that some GM drought resistant maize had saved what was left of the US maize crop that year, this does not seem to be the case. Some new conventionally bred varieties were sold in 2011 with these traits. Currently an internet search suggests not much has changed and all the GM crops in production cover the same traits mentioned above. Its the cosy link between agro companies selling you a crop that is resistant to a herbicide they produce that is a large part of the reason that GM is so controversial, in my view. Their claim that using GM herbicide resistant crops means the farmer will use less herbicide is not logical. In addition many of the staple crops that people rely on the developing world are left out of any technological developments. To be fair in a few years this is going to change with the introduction of “golden rice”, rice with vitamin A engineered in. This rice has had charitable and biotech company development input.
The second major limitation of GM is it does not overcome the huge oil dependency of agriculture. The graph below is a good illustration of this ( taken from “Global food waste not, want not”. IME 2013)
As you can see the amount of energy due to human effort doesn’t show up on the graph (its just 6MJ!) and the energy due to other fossil fuel dependent factors are huge. Even if you could remove the fertilizer component (see below) this would still leave over half the energy to be replaced with non-fossil fuel based sources.
Leaving aside ethical considerations GM has a number of biological limitations. The first is where the foreign DNA ends up in the plant genome. For one gene this probably doesn’t matter. Cells where the introduced gene has ended up in the middle of another critical existing plant gene probably won’t grow. But in another cell in the same culture it may have ended up somewhere else within the plant genome and these viable cells are selected then grown on into plants. Its when you want to put multiple genes in plants this would become more of a problem. The other obvious limitation is the fact that you can only transfer a few genes (golden rice is 3). Many of traits large agro-companies or charitable organisations would like to engineer into plants involve large families of genes.
The “holy grail” of plants with a large gene transfer requirement is that of legumes. These plants which include beans, peas, soya, peanuts and some trees have symbiotic relationships with bacteria in their roots. These bacteria fix nitrogen from the atmosphere into the soil. The argument goes putting this capacity in plants that require large amounts of fertilizer (e.g. cereals) would save both money and the declining resource used to make it (e.g. natural gas). However, the relationship between the plant and bacteria is an extraordinarily complex one and involves major changes in the structure of both parties. These changes involve large numbers of genes. In the case of the plant the number is in excess of 40. For the bacteria its around 20. Currently nothing like this number of genes can be transferred into plants. However, the complexity is not just the shear number of genes required that may make the plant non-viable by ending up slicing through vital genes. The other difficulty is that a whole series of other DNA sequences are required to switch the genes on/off have to go with them, possibly in other parts of a particular chromosome or even different ones if translocated. In addition these genes operate as groups and have to be able to interact with one another. Lastly considering climate change we may need to engineer plants with both drought and flood resistance. Again this would take multiple gene transfers into the same plant. This is not possible at present and probably involves synthetic biology.