Discoveries may indicate 'refuge strategies' — a commonly used defence against resistance — may become less effective
[BOGOTÁ] Genetic mutations in pests that allow them to develop resistance to genetically-modified (GM) crops may be much more diverse in field conditions than in laboratory tests, according to a study.
Laboratory tests are commonly used to develop strategies to fight emerging resistance in plant pests but these new discoveries suggest that such testing itself may, in this case, be insufficient.
The newly discovered mutations may also mean that a commonly used strategy for reducing resistance may be less effective than believed, according a study in Proceedings of the National Academy of Sciences, published last month (11 June).
Haonan Zhang, a scientist from Nanjing Agricultural University in China, and his research team, looked at genetic mutations in the cotton bollworm (Helicoverpa armigera) taken from fields of genetically modified (GM) cotton in northern China, and found that the bollworm has more diverse genetic mutations — allowing it potentially to survive on GM crops — than previously thought.
As well as the recessive mutations previously observed during laboratory studies, researchers also identified 'dominant' mutations that can shield against toxins such as Bacillus thuringiensis (Bt) — a naturally occurring microorganism that produces a toxin which only kills organisms with alkaline stomachs, namely insect larvae — and other insecticides.
This means that a single copy of a mutated gene is enough to confer pest resistance on its offspring.
It may also mean that a commonly used defence against resistance — a 'refuge strategy' in which GM fields are flanked by non-GM plants, allowing non-resistant pests to thrive and mix with resistant ones, thus driving the overall numbers of resistant pests down — are less effective than previously though.
"Dominant resistance is more difficult to manage and cannot be readily slowed with refuges, which are especially useful when resistance is recessive," said Bruce Tabashnik, head of entomology at the University of Arizona, and co-author of the study.
Tabashnik added that in addition to known mutations, the team had found "lots of other mutations, most of them in the same gene, but one in a completely different gene."
"We want to anticipate what genes are involved, so we can proactively develop strategies to sustain the efficacy of Bt crops and reduce reliance on insecticide sprays. The implicit assumption is that what we learn from lab-selected resistance will apply in the field."
Today, that assumption has been challenged, but rising levels of resistance in cotton fields may offer new ways of understanding what is happening, said Tabashnik.
Graham Head, head of global insect resistance management at Monsanto, a promoter of Bt cotton seeds, told SciDev.Net that the early detection of resistance is an important goal.
But he added that Zhang's study does not establish a direct relationship between these new genetic mechanisms and larvae's true ability to survive in cotton fields.
Prince Awele Odor ( Nigeria )
30 July 2012
Sinclair ( Sweden )
6 August 2012
The genetic resistance phenomenon as described in the Chinese/US article is likely to be a consequence of a NATURAL selection process and a NATURAL mechanism by which organisms survive under changing environmental conditions (cf Darwin). What is it about GMOs which you maintain makes them DEADLY? The fact that monitoring and other detailed studies are being carried out to investigate the genetic implications of GM crops on the potential infestation status of pests through open scientific dialogue is a sign of a sustainable approach to acknowledging the real situation in the field and avoidance of assumptions that what pertains in the lab extrapolates to the field. It is by doing such research work it enables more appropriate crop management strategies and enables the benefits of GM technology to be realised. Remember that organic production of foods and other biological produce on a large field scale might only be possible in the future using GM technology (enabling production within reasonable quality boundaries without incurring the need for agrochemical inputs). There is insufficient land for everyone on the planet to produce their own food in a totally organic way. So the question is reiterated: what evidence do you have to state categorically that GM foods are DEADLY? Where is the evidence for that assumption? One had better get the hard factual evidence first before persuading a hungry world the pervading deadliness of GM crops.
BE ( United States of America )
20 August 2012
The Green Revolution displaced pulses, an important source of proteins, and oilseeds, thus reducing nutrition per acre.
Hunger and malnutrition are man-made. They are hardwired in the design of the industrial, chemical model of agriculture. But just as hunger is created by design, healthy and nutritious food for all can also be designed, through food democracy.
We are repeatedly told that we will starve without chemical fertilisers. However, chemical fertilisers, which are essentially poison, undermine food security by destroying the fertility of soil by killing the biodiversity of soil organisms, friendly insects that control pests and pollinators like bees and butterflies that are necessary for plant reproduction and food production.
Industrial production has led to a severe ecological and social crisis. To ensure the supply of healthy food, we must move towards agro-ecological and sustainable systems of food production that work with nature and not against her. That is what movements that promote biodiversity conservation, like our NGO Navdanya, are designing on the ground.
Industrialisation of agriculture creates hunger and malnutrition, and yet further industrialisation of food systems are offered as a solution to the crisis. In the Indian context, agriculture, food and nutrition are seen as being independent of each other, even though what food is grown and how it is grown determines its nutritional value. It also determines distribution patterns and entitlements. If we grow millets and pulses, we will have more nutrition per capita. If we grow food by using chemicals, we are growing monocultures — this means that we will have less nutrition per acre, per capita. If we grow food ecologically, with internal inputs, more food will stay with the farming household and there will be less malnutrition among rural children.
Our agriculture policy focuses on increasing yields of individual crops and not on the output of the food system and its nutritional value.
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