Can we coexist?

posted in: Syndicated | 0

With religious wars around the world erupting almost constantly, you might be feeling grateful that you live in a country where there is separation of church and state. But dont rest too easy, another conflict is brewing- this time in agriculture.

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Twenty years ago organic farmers in our area began growing specialty sunflowers to sell for cut flowers. Although most of the pollen from organic sunflowers does not travel further than 3 meters, some of it can travel up to distances of 1000 meters, which can cause problems for growers of certified sunflower seed. If stray organic pollen should land on a sunflower grown for seed and hybridize with it, the resulting seed will no longer be purebred, reducing the value of the crop. This is the reason that sunflower seed growers in the valley were concerned about gene flow from organic sunflowers.

The certified seed growers and organic flower growers came to an agreement.

The seed growers gave the organic growers sterile seed that gave rise to flowers with no pollen- thus eliminating the risk of gene flow. This compromise offers a good example of how discussions among neighbors can lead to mutual benefits. California farmers grow 350 recognized crop and livestock commodities under a variety of farming conditions, often on adjoining fields. Good communication and common sense is key to peaceful coexistence. Can we apply these principles to all crop production methods–GE, organic, and conventional?

According to some in the organic community we can and we must. Setting a threshold for acceptable pollen drift (as the National Organic Program Standards has done for pesticide drift- and here it is important to keep in mind that some pesticides are toxic to humans and other animals whereas GE alfalfa pollen is not), will foster coexistence and address the concerns of organic growers who deserve assurance that their markets will not be affected by small amounts of pollen flow. Others in the organic community, say no, GE and organic production methods cannot coexist.

Journalist Dan Charles addressed these issues in a recent National Public Radio story about afalfa genetically engineered to tolerate the herbicide RoundUp. The story is timely because the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service recently announced that it will allow American farmers to plant genetically engineered alfalfa, which is widely used as feed for dairy cows and horses.

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Weeds are a major limitation of crop production globally, as they compete for nutrients and sunlight. Many are also toxic to animals so forage that is contaminated with weeds can be problematic for the farmer and her cows. One method to control weeds is to spray herbicides that kill them. Many of the herbicides used over the last 50 years are classified as toxic or slightly toxic to animals and humans (classes I, II and III). Some newer herbicides, however, are considered nontoxic (class IV). An example of the latter, the herbicide glyphosate (trade name Roundup), is essentially a modified amino acid that blocks a chloroplast enzyme (called 5-enolpyruvoyl-shikimate-3-phosphate synthetase [EPSPS]) that is required for plant, but not animal, production of tryptophan. Glyphosate has a very low acute toxicity, is not carcinogenic, breaks down quickly in the environment and thus does not persist in groundwater.

Some crop plants have been genetically engineered for tolerance to glyphosate. In these herbicide-tolerant crops, a gene, isolated from the bacterium Agrobacterium encoding an EPSPS protein resistant to glyphosate, is engineered into the plant. Growers of herbicide-tolerant crops can spray glyphosate to control weeds without harming their crop.

Although herbicide-tolerant crops do not directly benefit organic farmers, who are prohibited from using herbicides, or poor farmers in developing countries, who often cannot afford to buy the herbicides, there are clear advantages to conventional growers and to the environment in developed countries.

One important environmental benefit is that the use of glyphosate has displaced the use of more toxic (classes I, II and III) herbicides. For example, in the Central Valley of California, most conventional alfalfa farmers use diuron (class III) to control weeds. Diuron, which also persists in ground water, is toxic to aquatic invertebrates (EXTOXNET – EXTENSION TOXICOLOGY NETWORK 1996). Planting of herbicide tolerant-tolerant alfalfa varieties is therefore expected to improve water quality in the valley and enhance biodiversity (STRANDBERG and PEDERSON 2002). Switching from Diuron to glyphosate in alflafa production is predicted to have environmental benefits as measured in environmental impact and likely health benefits for farmworkers (FERNANDEZ-CORNEJO and MCBRIDE 2002).

One drawback to the application of herbicides is that overuse of a single herbicide can lead to the evolution of weeds that are resistant to that herbicide. The evolution of resistant weeds has been documented for herbicide-tolerant traits developed through selective breeding, mutagenesis and genetic engineering. To mitigate the evolution of weed resistance and prolong the usefulness of herbicide-tolerant crops, a sustainable management system is needed. Such approaches require switching to another herbicide or mixtures of herbicides or employing alternative weed control methods (COMMITTEE ON THE IMPACT OF BIOTECHNOLOGY ON FARM-LEVEL ECONOMICS AND SUSTAINABILITY and NATIONAL RESEARCH COUNCIL 2010). Implementation of a mandatory crop diversity strategy would also greatly reduce weed resistance. Newer herbicide-tolerant varieties will have tolerance to more than one herbicide, which will allow easier herbicide rotation or mixing, and, in theory, help to improve the durability of effectiveness of particular herbicides.

Most forage experts believe the economic issues related to pollen flow between genetically engineered and non-genetically engineered crops can be resolved peacefully without resorting to steps that are extraordinary or expensive. Just as our neighbors managed to do 20 years ago.

Follow Pamela Ronald:
Pamela Ronald is Professor of Plant Pathology at the University of California, Davis, where she studies the role that genes play in a plant’s response to its environment. Her research focuses on the genetics of rice. With her husband, she co-wrote Tomorrow's Table: Organic Farming, Genetics and the Future of Food. She writes a blog of the same name.