Headline news for GM this week was a new study on resistance to potato blight, the results of 3 yrs of field trials at the John Innes Centre in Norwich.
The paper in the Proceedings of the Royal Society B compared non-transgenic Desiree potato plants with GM plants. When blight conditions were severe in 2012, it dramatically reduced yields in the non-GM varieties. Tubers from each block of 16 GM plants weighed 6-13 kg while the non-GM tubers weighed 1.6-5 kg per block.
The GM variety was Desiree with a gene added from a wild South American relative.
Potato blight is caused by the fungus-like organism Phytophthora infestans and spreads most readily in warm and humid weather with rain. It is the most important disease of potatoes, and caused the Irish potato famine of the 1840s.
Different potato varieties have different levels of resistance to blight, and there are already varieties which have high resistance (this link is to a ‘nor-for-profit company’, which is interesting in the context of my ‘profit for purpose’ post). The same varieties aren’t necessarily resistant to foliage blight and tuber blight. There also seems to be the problem that a potato is by no means just a potato – varieties are used for different things, and the blight resistant varieties are apparently not popular with consumers.
The Potato Council is currently working on re-testing varieties to see how resistant they are to the recently-emerged strain of blight: blue 13. This new dominant strain is more aggressive than most other strains.
Existing resistant varieties which aren’t GM seemed to be the centre of the inevitable disapproval. However, whether or not GM is the answer to controlling blight, it seems clear to me that an answer is still needed.
The fact that the Potato Council has a Fight Against Blight map to warn farmers of outbreaks suggests that there may be resistant varieties, but we still have a major problem.
I was shocked recently to be told how much potatoes get sprayed with in the UK – here are the pesticide stats for Scotland and this recent advice to farmers about fungicide use will give a bit of an idea about fungicides. In northern Europe, farmers typically spray a potato crop a staggering 10-15 times, or up to 25 times in a bad year.
Costs for late blight control have been estimated in the Netherlands to be around 330 Euros per hectare per year for chemicals – the decision to spray isn’t being taken lightly.
In summary, I am sure that this is an issue I will return to, but my assessment so far is that we have various options (not mutually-exclusive): invest in research to combat blight through GM, invest in research to combat blight through without GM, change our tastes to eat more varieties with blight resistance… I’m willing to be persuaded of any of those, but what doesn’t seem wise is business as usual, growing non-resistant varieties and spraying them so regularly.
As for the former options – I would very much welcome comments in support of any of them.
Professor Jonathan Jones, lead author of the study, explained why he thinks GM is the answer: “Breeding from wild relatives is laborious and slow, and by the time a gene is successfully introduced into a cultivated variety the late blight pathogen may already have evolved the ability to overcome it.”
Jonathan D. G. Jones et al. (2014) Elevating crop disease resistance with cloned genes. Proceedings of the Royal Society B DOI: 10.1098/rstb.2013.0087