Utterance of “GM crops” usually has the effect of inciting anger in the public mind, while scientists shake their heads at public misunderstanding.  Although in principle I strongly favor the development of GM crops if they’re used to make agriculture more sustainable, the multinational companies that give us these technologies have really botched the relationship with farmer and public.  These companies can now only find camaraderie with scientists, business folk, and lawyers.

Two recent papers have reported the benefits of one GM crop: Bt cotton.  The ‘Bt’ stands for Bacillus thuringiensis, a Firmicute bacterium capable of producing a crystal toxin that, upon ingestion, punches holes in the digestive tracts of insects (and even some nematode worms).  The gene encoding the Bt toxin (at least one form of it, there is a diversity of toxins) has been added to the cotton genome so that the plant can now express this toxin.  The good thing is that only insects that are feeding on the cotton will be exposed to the toxin, thereby killing the cotton pests but not the surrounding populations of beneficial insects.

Kathage and Qaim (PNAS 109: 11652; http://www.pnas.org/content/109/29/11652.full) present data from Indian cotton farms that suggest overall cotton yield has increased during their 6 years of monitoring, resulting in a larger profit for individual farmers.  This increase in profit even accounts for the 2-3 fold higher cost of Bt cotton seed.  This has been accompanied by an increase in a measure of Indian living standards.

Lu et al.* (Nature 487: 362; http://www.nature.com/nature/journal/vaop/ncurrent/full/nature11153.html) analyze how natural aphid populations, and their predators, are affected by Bt cotton.  The idea here is that because Bt cotton has its own internal insecticide factory, there is no need for spraying of external insecticides, and because spraying insecticides kill beneficial insects too, planting Bt cotton results in recovery of natural populations of insects that prey on the destructive Bt-resistant aphids.  Lu et al. found that, indeed, natural aphid predators increase in abundance and aphids decrease in abundance when Bt cotton is planted (or if regular cotton is planted but no insecticide is applied). 

These studies both shine a bright light on the benefits of GM technology.  But questions remain.  Planting only one variety of cotton (GM Bt cotton) around the world surely has consequences, from eliminating locally adapted varieties of cotton to restricting the freedom of farmers.  Furthermore, it is known that resistance to Bt toxin can evolve readily in many populations of insect pests.  There are management strategies to deal with this, where acres of non-Bt crops are planted to help maintain Bt-sensitive populations.  But is this enough?  How many years will Bt crops be a viable option?  As a scientist I welcome the outcome of this experiment, but I also find gambling with agriculture a bit nerve wracking.  Then I ask myself: what are the alternative options?  My mind comes back to the original problem of explosive insect pests enabled by vast fields of monoculture. 

*My apologies for this not being open access.  It was my goal to only blog about research everyone could access.  Inevitably, this goal will not always be achieved.