The fight against potato blight
As a new blight resistant GM potato has arrived on the market, pressure for the EU to relax regulation on genetically modified crops is gaining momentum. It’s being hailed by some scientists as the most efficient solution to the onset of the late-blight pathogen, Phytophthora infestans. But in the rush to celebrate another GM innovation, the existence of non-GM blight resistant varieties has largely been overlooked by the mainstream media.
Despite the justification that the GM potato has ‘full resistance’ to blight, which destroys £60 million worth of potatoes each year, their long-term impact on farmland and human health has not been adequately investigated. The benefits are singularly focused on the immediate short-term guarantee of providing disease resistance, while the long-term picture remains founded on ‘scientific prophecy,’ rather than robust scientific evidence.
It appears that going down the GM road could potentially cause as many problems as it solves: the unpredictable consequences of transgenic mutation; the potential threat of weed resistance like those effecting GM monocultures in the US; the fact there is little public appetite for GM foods in the UK; and the long-term negative impact on biodiversity in farming, which comes from relying on monocultures of a small range of crops, GM or not.
Phil Sumption, at the Organic Research Centre, is concerned about the bigger picture of a GM solution, ‘The problem with GM potatoes is that you are going down a one or two variety route, rather than investing in diversity, which is a potential risk when the resistance breaks down.’ As the pathogen evolves, the GM potato will need to be adapted to maintain its resistance to the disease. Large-scale monocultural farming would remain particularly vulnerable to the threat of blight, if it simply relies on one GM-resistant variety.
To create the new GM potato, scientists used the popular variety, Desiree, for the GM control and added resistant genes from a wild South American relative. They were prohibited from tasting the GM potato but argue that the taste would not have been affected by the modification. However, the developers do not appear to be particularly concerned about whether or not there is a market in Europe for GM vegetables. A 2010 Eurobarometer Study found that only 27% of Europeans are willing to buy GM – hardly evidence of a burgeoning desire for these developments.
According to Genewatch UK, £3.2 million of taxpayers’ money has been spent on research this blight-resistant variety to date, which was conducted by The John Innes Centre and The Sainsbury Laboratory over a three year period. More funding will be required to maintain resistance, by ‘stacking’ more resistant genes on top of each other, as the pathogen adapts. The new GM potato will never be the silver bullet of blight.
So the question remains whether the cost is necessary, or even worthwhile, when non-GM blight resistant varieties have been developed by breeders and are currently available commercially. ‘There are conventional breeding programmes such as the Sarvari Research Trust and Agrico that are producing good quality blight resistant potatoes that should be acceptable to the market,’ says Phil Sumption.
Bioselect UK have successfully bred some highly resistant varieties, one of which, called Athlete, is being sold by Marks & Spencer. Riverford Organic Farms grow and sell a range of good quality, highly-tolerant varieties such as Valor and Orla found listed in the Niab seed catalogue, which according to roots manager Alan Edyveane are ‘good all rounders’ in taste and vigour.
In particular, The Sarvari Trust based in North Wales, have specialised in developing a range of blight resistant potatoes called Sarpo over the last 10 years. Like the GM potato they do not require the use of fungicides, although they cannot claim to be ‘fully resistant.’ However, the Sarpo Mira variety has been analysed using the techniques of molecular genetics, and has been found to have at least 5 resistance genes, equivalent to stacking in the GM option.
Scientists have criticised current conventional breeding methods as ‘slow and inefficient.’ Sarvari Trust director, David Shaw, comments that though ‘it is always going to be a fact that conventional breeding is slower than GM breeding… I would say there are benefits of Sarpo varieties that are not generally recognised.’ The Sarpo Mira and Axona varieties are particularly low-input with high resistance to common viruses as well as blight, weed smothering vigour and extended dormancy (the potatoes can be stored over winter without refrigeration and without anti-sprout chemicals).
The Savari Trust also has endeavoured to develop varieties that minimise growers’ carbon footprint in a heavily agro-chemical reliant industry ‘A GM solution, as with conventional varieties, would still require… additional agro-chemicals to destroy viruses, weed competition and suppress sprouting in store.’
The taste and texture of Sarpo varieties are different from what consumers are used to, but in light of a recent sampling of the Sarpo varieties at River Cottage, the Sarpo Axona makes an excellent mash and the Sarpo Shona are ‘one of the best chipping potatoes I have used,’ according to head chef, Gelf Alderson.
There are also a range of methods to fight blight that don’t involve a blight resistant potato:
Martin Wolfe, owner of Wakelyns Farm, integrates standard farming practices with tree production, so that the trees and crops interact to support each other’s growth and encourage biodiversity. One of the key techniques of agroforestry is alley-cropping where land is divided into crop ‘alleys,’ separated by tree production hedges orientated north/south to minimise shading of the crop. ‘The tree hedges act as a partial barrier to blight pathogen spores being blown in on prevailing south-westerly winds. This slows the rate of epidemic development delaying it up to three weeks over the key bulking period for potatoes, which is crucial,’ says Wolfe. This delays mowing off infected foliage, allowing the potatoes to receive the nourishment and sugars to produce a sufficient yield.
Rotation and mixed varieties
Using a long rotation of crops, and growing mixed varieties of potatoes side by side, both help to delay or deter blight. Both practices are critical in organic farming. ‘In the field we alternate rows of different varieties or beds, so rows of resistant ones can protect more susceptible varieties,’ says Wolfe. Wolfe stresses the importance of rotation, since volunteer potatoes can persist for up to 2-3 years. ‘The two key things are to get rid of potatoes left over and make sure you have a good long rotation – standard hygiene really.’
Steve Townsend of Base UK, suggests building up the potatoes natural immunity through soil enrichment. This ensures the plant can utilise the nitrogen which may otherwise become food for the disease ‘You can reduce disease levels by providing better nutrition, we have our 5 a day and plants need theirs.’ He suggests a mixture of boron, manganese, zinc, copper, magnesium, sulphur, molybdenum, phosphate and potassium, all in good measure.
According to Ulrich Schmutz from Garden Organic, picking earlier varieties which can be harvested before blight occurs, wider spacing of plants to allow more airflow and chitting, (getting potatoes to grow shoots before planting, which gives them a head start so they can be harvested earlier) all help to protect against blight.
Ultimately, the array of techniques currently in practice among commercial growers to prevent potato blight makes the need for a GM solution appear redundant and potentially reckless, especially when considering the broader implications of resistance, pesticide-use, and corporate ownership of our food systems. Before we embark on a slippery slope towards a GM future, shouldn’t we question whether it’s really better than what we already have in our tool kit?
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