HOST PLANT RESISTANCE
Host plant resistance to pests has long been one of the main tools used in pest control. In fact, most plants are resistant to most pests!! Even for pests to which a plant species is susceptible, the plant species often contains a genetically controlled variablity in degree of susceptibility. This allows plant breeders to use classical plant breeding techniques in which, at every generation only those plants that are most resistant are crossed (mated), and so on over the generations. This allows resistance to increase over the generations.
For example, wheat resistance to rust fungus is genetically controlled, with different genes controlling resistance to different rust races. Breeders, using conventional breeding techniques, can thus pack a number of resistance genes into one wheat variety (just by crossing varieties that contain different resistance genes). Each year, pest warning services forecast which rust races are likely to be most problematic that year (similar to the fashion in which the medical sciences forecast which flu strains will be most common in a given year), and growers then plant wheat varieties that have resistance to those rust races. On the down side, single gene resistance like this (a single gene encoding resistance to a single rust race) seems to be relatively easy for fungi to cope with by evolution, so the useful life of a new wheat variety is often only about 4-5 yrs. (Click on resistance for reminders on how evolution of resistance to pesticides takes place; it is the same with rust fungi evolving resistance to the plant's resistance gene.)
Sometimes host plant resistance is more exotic; for example, at Cornell University, breeders have been developing a potato whose stems and leaves are covered with sticky hairs that trap insects and immobilize their legs and mouths. (Again, this is by classical plant breeding, crossing at every generation the hairiest and stickiest potatoes....) In experimental situations, the hairy potato can cut damage by destructive aphids in half!
Genetic engineering offers much potential benefit (i.e. improved productivity or nutritional quality, increased pest control with decreased pesticide use) but also much potential risk. I attempt here to give you a quick overview, but suggest that you read more widely on this topic as well; several relevant articles are on the supplementary reading list for this section of the course, and a couple of your assigned readings and their literature cited sections will also provide you with more information. The National Research Council, the research arm of the US National Academies of Science, published an overview report on genetically modified crops in the year 2010, entitled The Impact of Genetically Engineered Crops on Farm Sustainability in the US. While some argue that this report is overly optimistic about the costs and benefits (economic and environmental)of such crops, the report does strive for balance. A word of caution: you can find all KINDS of "looney tunes" websites that claim to be authoratative about the use of genetic engineering in agriculture, both on the "pro" and "con" sides; please read critically!!
There is so much to learn in this field, and it changes by the minute. I attempt to keep information here up-to-date, but am able to do only an annual update (at best)..............so; read with caution!
Genetic engineering can be used to enhance natural plant resistance to pests and diseases as can also be done with conventional cross-breeding among plants or varieties within a given species. In such cases, genetic engineering can simply speed the process by transferring the genes directly rather than relying on trial and error, as in traditional cross breeding. Even in the case where genes are moved from one plant of a given species to another plant of the same species using genetic engineering, however, consequences can differ from those that would result from traditional cross breeding. For example, if multiple copies of a given gene are added rather than single copies, effects can differ. "Position effects" can also be important -- a gene's action -- even whether it gets "turned on" or not -- can vary depending on the identity of its neighboring genes; using genetic engineering, the area of insertion for the transferred gene(s) is typically not as predictable as it is using conventional breeding wherein genes move with entire chromosomes, rather than in isolation.
Use of genetic engineering to facilitate movement of genes within a species or variety -- or from one unrelated species to another -- is facilitated -- basically made possible -- by genomics. Genomics involves sequencing a genome and determining the location and function of various genes. Scientists can then excise the gene or genes known to produce a useful product and insert it into another plant of the same -- or a different species. For example, the rice genome project recently sequenced the entire rice genome. Now, researchers can use comparative genomics to determine the likely function of various gene sequences (from what we know of their functions in other plants, such as Arabidopsis, one of the "lab rats" of plant genetics. Researchers can then amplify the genes or knock them out, and look for phenotypic expression to see what those genes do. Another way to discover the function of the genes involves finding or creating mutants of those genes and examining the consequences in terms of gene expression. This capability of determining gene location and function in a given species has tremendous potential. For example, let's say that researchers determine that a gene is important in influencing responses to nutrient availability or to some other environmental factor. That gene could then be used to create a variety of the crop that can tolerate that particular environmental factor.
That is, genomics is useful in "smart breeding" or "marker assisted selection" (MAS) - if we know know where the genes are and what they do, cross breeding can then be used to draw the traits out, or genetic manipulation can be used to insert the desired genes into a recipient. Genomic sequencing allows location and isolation of single genes and deliberate modification of their expression to see what they do. Maps of a plant's genome are searched for sequence markers that are closely associated with a trait such as disease resistance (like scanning for a certain barcode), and hence are associated with a gene or group of genes that confer that trait. These markers can then be used to screen breeding stock and progeny from traditional crosses before they are ever planted out; instead of waiting until the plant is mature to see if the desired traits are being expressed, breeders can screen small pieces of leaf tissue from very young plants to determine whether the marker(s) [and thus the genes of interest] are present or not. That is, MAS really speeds breeding, by eliminating much of the trial and error and by allowing determining whether or not a gene is present very early in the plant's life (Catalyst fall 08). The pace of such facilitated breeding is accelerating as more and more crop genomes are sequenced and genetic screening tools become cheaper and faster. The gene of interest can also be removed and inserted into the same or a closely related species (the genes would basically be homologous). The result is, then, similar to results that could occur from natural mutation -- or even cross breeding -- and is less radically different than other transgenics described below. For example, genes for blight resistance found in the Chinese chestnut can be inserted into American chestnuts using genetic technology, rather than using cross breeding, which is relatively "hit or miss." The insertion of a gene or genes from a sexually compatible species into a recipient species is used to create what some refer to as "cisgenic" plants ([Science 6 May 2011] as opposed to "transgenic," which is the genetic modification of a recipient plant with a gene or genes from a sexually incompatible plant or another organism, as would not occur in nature.
So, some plants that result from genetic engineering are not "unnatural" -- these "cisgenics" could be produced using traditional cross breeding -- or produced in nature as plants interbreed. Quite different, however, is the use of genetic engineering to add traits that aren't a normal part of the plant's genome (genetic composition). Use of these transgenic crop plants (commonly referred to as "GMO's" (genetically modified organisms) )is quite controversial.
HOW ARE GMO'S "MADE?"
A full answer to this question is beyond the scope of BI 301 and beyond the scope of my knowledge -- but some very useful descriptive articles are listed with supplementary readings... Briefly, the technique involves extracting DNA containing a gene or genes of known function and then inserting it into the recipient plant [BioScience May 2008]. The gene(s) are carried into the recipient using genetically engineered plasmids that contain the gene(s) of interest. (Plasmids are small pieces of circular DNA, found for example, in bacteria). The plasmids are then carried into plant tissue using "vectors" such as bacteria (commonly Agrobacterium) or viruses -- or "gene guns" which shoot nanoparticles made of gold, tungsten, or silica that have been coated with plasmids. Targets for the vectors are typically isolated, undifferentiated callus cell cultures or immature embryo cells geowing on nutrient media. In some cases, the gene(s) successfully incorporate into the recipient's DNA. Scientists can tell whether or not the gene was incorporated, because along with it there is usually spliced a gene for some selective marker -- such as a gene that confers antibiotic resistance. The cell cultures (or the plasmids, before they are vectored into the recipient] can then be treated with the selective agent -- say an antibiotic -- and the cells that took up the genes will survive the treatment, while most others will not. Because the genes are incorporated into embyonic or undifferentiated cells, they will then be copied with each chromosomal replication and cell division, and so will be found in every cell of the resulting mature indicidual. They thus become thus a part of the recipient's chromosome, and a part of the germline from then on.
HOW WIDELY ARE GMO'S USED IN AGRICULTURE?
Widely! Over the 11 years prior to 2007, acreage devoted to GMO crops in the US increased over 60-fold, making it one of the most quickly adopted farming techniques in modern history [Science 25 May '07]. There are now GMO consituents in ~ 70% of our processed foods in the US. Here's a bit of information on that trajectory:
By the summer of 1998, over 30 million hectares worldwide was planted with these crops. By 1999, 40, 50, and 45 % of acreage planted to corn, cotton, and soy,respectively, in the US was GMO. These crop plants are then used in the production of hundreds of foods, of course.
By 2005, about 49.8 million hectares of US farmland were planted in GMO crops, which constituted about 55% of the global crop area planted to GMO's. You can see the big change between 1998 (above) and 2005! In 2005, 52% of US corn acreage was planted to genetically engineered corn -- 26% of that to "Bt-corn" (described below), 17% to herbicide resistant corn, and the remainder to corn with both traits. (BioScience, June 2006) By 2003, ~ 80% of US soy acreage was planted to soy engieered to be resistant to glyphosate herbicide (as in "Roundup resistant soy"). (See below for more information on both types.). By 2011, these acreages in the US are up to ~ 94% of soy and ~ 75% of corn and cotton! In the US, most acreage planted to GMO crops is devoted to cotton, soy, canola and corn.
By 2006, about 100 million acres were planted to GMO crops, globally [Science 25 May '07], and more than a billion acres of GM crops were planted in the US across 1996 to 2007 (Science 25 Apr. 08). As of 2011, about 75% of global soybean acreage is planted to GMO soy (herbicide resistant).
Incidentally, transgenic and nontransgenic corn grain are not usually separated in the US corn production system, so most batches of corn contain some of each. We do export considerable quantities of such mixed corn to other countries (including to Mexico, the center of origin for maize and a hotspot of maize genetic diversity). A letter from the USDA accompanies such mixed shipments noting that they are may contain genetically engineered (GE) grain, and implying that, because the US has approved these crops for commercial scale production, they are safe. (BioScience, June 2006).
In the summer of 2012, Walmart raised a ruckus in some circles by announcing that it would be selling GMO sweet corn in its storee, corn that was engineered to resist either herbicides or insects or both [GT Aug 4, 2012].
Internationally, there is great variation nation to nation in the degree to which GMO crops have been accepted, as the following examples illustrate:
In some nations and for some crops, however, it appears that use of GMO crops is associated with decreased pesticide inputs -- it all depends on the crop and the circumstances (see examples, below).
Specifically with regard to herbicides, it appears that in the first years when herbicide resistant crops were planted, herbicide use in US did decrease, but then increased. Reasons for increases aren't certain, but might include the possibility that heavy reliance on the herbicide that the crops are resistant to causes changes in the weed species that comprise the weed communities (towards those that tolerate the herbicide) and also the possibility that weeds' increasing resistance to that type of herbicide makes it necessary to use more….
Interestingly, despite the widescale adoption of GMO crops in the US, few studies have assessed the farmer's "bottom line" -- that is, do they make more money when using GMO crops than when not? However, a study in 2002 in Iowa comparing costs and profits for GMO and non-GMO soy and corn found, as in 1998, that growers were not making more money with GMO crops than with non-GMO. The investigators compared costs such as fertilizer and pesticide and seed, and yields (and all other costs and benefits that they could.) For herbicde tolerant soy, they found that, with GMO beans, herbicide and weed management costs were lower, but seed costs were higher and yields were slightly lower, compared to non-GMO varieties. For Bt corn (against European corn borer), yields were slightly higher, but fertilizer and seed costs were higher. Thus, in neither case did farmers earn more money using GMO crops, compared to non-GMO crops. The question is, if the bottom line isn't improved by use of GMO crops (i.e., farmers make more money - or get higher yields at least) - why do farmers use them? Farmers say that they like the convenience of herbicide resistant crops - they can cover more acres more quickly when spraying and don't need to worry about weed management. For Bt corn, farmers said that they view it as an insurance policy in case there's an insect outbreak....
In India, however, the use of Bt cotton (cotton containing genes that code for production of an insecticide -- see below, including the recent emergence of insects that resist the toxin) has reportedly both decreased damage and increased yield. This may be at least in part because Indian farmers weren't using chemical controls widely on cotton before, so the use of Bt cotton was their first major control effort.
Concerns over the environmental and human hazards associated with "GMO's" have led to debates in governments in the US and elsewhere about testing, regulation, and labelling of GMO products -- see below (near the end of this section of notes) for more information on regulatory and testing issues. I'd like to mention a few things about some of the concerns, before moving to some specific examples of the use of GMO crop plants. This is, of course, one of those many cases where each person needs to make up their own mind about what they think -- my opinions are only that, and are presented below with that disclaimer!
First, in my view, it is important to distinguish concerns about the process used to produce the plant from the results of that process. Many people seem to react with concern to anything that has been "genetically engineered" (by which we mean has had genes inserted into its genome through a means other than by cross-breeding). However, as described at the outset, above, in some cases, genes inserted are actually from the same species or variety of crop plant, in which case the engineering is basically used to speed a process towards a result that could be obtained by conventional breeding. In other cases, of course, the genes that are inserted using genetic technologies are genes from another species or kind of organism entirely. In this case, the resulting crop could not have been produced using conventional breeding techniques. The latter raises more concerns for me than do cases where the technology accomplishes a transfer that COULD happen "in nature." (Ethical issues about whether scientists should "play God" by using genetic technologies are not decidable by science -- but should surely inform scientific progress! There are also concerns about position effects associated with the insertion of genes....)
I also believe that the GMO situation is one where the precautionary principle should be invoked. Once released, GMO organisms (or their genes, as carried by pollen, for example) simply cannot reliably be recalled!! The release of such organisms -- particularly on commercial scales -- is tantamount to us conducting a major, and potentially risky, experiment, in my view. You may be familiar with the name Erwin Chargaff? Remember from basic biology, "Chargaff's rule" -- that, in DNA, the proportions of adenine = those of thymine, while proportions of cytosine = guanine (A=T; C=G)? He is sometimes referred to as the "father of molecular biology." Even Chargaff has concerns about genetic technologies -- he has been quoted as saying, "I have the feeling that science has transgressed a barrier that should have remained inviolate." and also as saying that their release is an uncontrollable experiement that could constitute, "...an irreversible attack on the biosphere." Pretty strong stuff!
Do potential benefits outweigh risks? See what you think! The debate is extremely polarized; one side perceives excessive regulation as delaying the provision of benefits that could otherwise be provided by GMO crops, while the other side believes that adoption is proceeding too rapidly and without adequate safeguards.
As examples that follow will illustrate, I believe that new genetic technologies may have the potential to help with some important agricultural issues. For example:
However, there are many concerns as well, listed briefly below and elaborated in subsequent pages of these notes.
A SPECCIAL NOTE ABOUT IMPLICATIONS OF GMO CROPS FOR ORGANIC GROWERS: You will recall that foods labelled as "organic" are to have been produced without the use of GMO crop constituents and are not to be GMO crops themselves. However, as we will see, below, in the section focused on herbicide-tolerant GMO crops, it is widely recognized that it will be almost impossible to prevent "genetic pollution" of organic fields by the GMO's, either via the spread of pollen or seeds that inadvertently reach the fields or GMO crops that are accidentally mixed with non-GMO crops after harvest. The latter happened in the year 2000, when a GMO corn variety, "StarLink," which had been approved only for animal feed, was found in taco shells and in ~ 10% of the US corn supply, causing massive recalls. [Science 8 April 2011]. Thus, USDA, in administering the "organic" label specifies that growers may not plant GMO crops, but the label does not necessarily mean that there are zero transgenes in organic products; if transgenic plants accidentally end up in an organic grower's field, the product can still be labelled as organic. So far, however, the UDSA has not set a standard for a percentage of transgene pollution that is allowed. A private, non-profit group, the Non-GMO project, has, however, set its own standard, which is less than or equal to 0.25% contamination for seed and less than or equal to 0.9% contamination for foods and ingredients. Manufacturers who are certified to test for transgenes can use the Non-GMO label if their product satisfied these criteria. SO, if you want to be as sure as you can that you aren't eating significant quantities of GMO foods, look for that label...
How can the risks of genetic pollution be minimized? It is widely recognized that plans for "coexistance" between GMO and organic crops are needed. The required isolation distances will vary with the crop and its pollination system, as that affects how much distance should be provided between fields growing GMO crops and organic fields. Soybeans, for example, are self-pollinating, so closer proximity could be allowed for them than for a crop such as corn, which is an outcrosser and wind pollinated, or alfalfa, which is pollinated by insects. Scientists try to assess the necessary distances by surveying for the existance of transgenes in organic crops, by tracking the movements of pollinators (for example, "dusting" the feet of bees with colored powder), and by deliberately planting nontrangenic plants at varying distances from GMO fields and then testing them either genetically or by treating their progeny with herbicide to see if they have acquired the herbicide resistance [in the case of herbicide-resistant GMO's, of course!].
Also needed are defined USDA standards for how much contamination can be tolerated while still using the organic label -- and for exporting crops to nations who refuse to import GMO crops or products.
Organic groups want more specific regulation over genetic pollution and want the biotechnology industry to share the cost of preventing and assessing gene flow. As it stands currently, organic grops argue that they basically pay those costs now: they pay for testing their crops for transgenes; use their own land to plant buffer strips to decrease pollen movement; and sometimes plant at a less optimal season to avoide the time of peak gene flow, with suboptimal planting times potentially affecting yield or increasing their risks of bad weather. Organic groups also want the biotechnology companies to establish a compensation fund for damages if their crops can't be sold as organic because of excessive contamination. The industry is basicaly resistant to this, and, at least so far, USDA seems to lean towards the industry side in the debate [Science 8 April 2011].
Other approches to decreasing risks of genetic pollution include trying to identify genes that make it so that traditional varieties cannot be cross pollinated by GMO's -- that is, to "fence them out" genetically. Various kinds of cross-incompatibility research are discussed in the Science article referenced above (on the supplementary reading list -- see Stokstad). Research is also going on to try to modify GMO crops so that they can't spread pollen, or to put the transplanted genes into chloroplasts, which are maternally inherited, so won't be part of the pollen. Such research efforts are expensive, however, and there is little to be gained from the industry perspective -- the organic growers are the primary beneficiaries -- so there is little incentive to put much resource into these efforts.An article in Science (25 Apr 08; see Marvier et al. on the supplementary reading list) makes a convincing case that we are undertaking a grand experiment in our deployment of GMO crops, but without the record keeping that will enable us to really learn from the experiment. For example, we don't keep close enough track of what crops were planted where, and when, and of associated indicators of agroecosystem condition. If we did do a good job of such record keeping, we could carry out a rigorous cost : benefit analysis -- as it is, we cannot. We need data to help us understand patterns in relations between use of GMO crops and environmental indicators (water quality, pest resistance, biodiversity) -- and to help us understand tradeoffs from the farmer perspective (dollar costs, time, crop looses, etc.)
EXAMPLES OF USES FOR GMO CROPS
The vast majority of the global acreage devoted to GMO crops is planted to crops that are either herbicide resistant, resistant to insects or both.
Insect or disease resistance
Genes from Bacillus thuringiensis (a bacterium, fondly abbreviated as "Bt")have been used in various ways to enhance plant resistance to lepidopteran pests. (We talked about toxins produced by this bacterium when we talked about biocontrol agents.)
Another concern -- will these genes "escape" and get into weeds, making them even tougher? Similar concerns apply to other GMO crop varieties.
How do genes "escape" into weeds or other plants ? Basically through hybridization between the cultivated crop and its wild relatives, some of which are weeds. Pollen contains genes, of course, and it moves around, whether by wind or insect or other vectors. It turns out that genes can move from crops to their wild relatives more easily than was previously thought. Scientists used to think that there was only a minimal chance of such gene transfers occurring, because first generation hybrids between cultivated crops and their wild relatives are usually sterile. However, recent studies using marker genes have found that high percentages of wild relatives growing near their cultivated relatives acquire the marker gene within a short time (as many as 50% of the wild plants may acquire the marker). Thus, gene flow from cultivated crops to wild relatives is not as rare as was previously thought. In addition, research shows that the genes from the GMO plants do pass to the relatives, and do persist over generations (e.g., in oats and radish and their wild relatives) (see creeping bentgrass case, below, under herbicide resistant GMO heading).
As more and more transgenic crops are approved for field tests (on the order of five to seven new transgenic crop plants approved for field testing every 6 months for the past few years), it is increasingly likely that such movement will occur. The fear is that these genes will make the wild relative weeds resistant to pathogens and insects that help to keep the weeds under control. Gene movement like this isn't of major concern for all transgenic or otherwise genetically engineered characteristics, of course; for example, if genes that make tomatoes ripen more slowly moved to weedy relatives, impacts might be minor. (Might be - we'd want good ecological understanding before we could say "would be minor!") (See mention below, under herbicide-resistant GMO's, of specific evidence of genes moving, via pollen, farther than imagined!) Further, many crops don't have wild relatives that could hybridize with the transgenic strains, so such movement wouldn't be of concern in those cases. (Corn, for example, has no wild relatives in the US -- but does in Mexico and in Central and South America.)
Mexican corn issues : The Mexican government (in 1998) banned the planting of transgenic corn anywhere in MX, because of concerns that genes from it (via pollen) would contaminate the center of origin of maize. There are many ancient types of corn in Mexico, which contain huge amounts of genetic diversity, and there are grave fears that these "land races" could be contaminated by genes from GMO varieties. However, despite the ban on planting of GMO corn in Mexico, some scientists claimed that they detected GMO genes (Bt - insecticide) in traditional strains or landraces of maize there. The foreign genes were detected using PCR - polymerase chain reaction - which amplifies particular snippets to enable their detection. Other scientists contested the claim of contamination -- and still others, subsequently, contested the claim of no contamination-- we'll see what time will reveal! (There was an excellent review of this issue in the June 2006 issue of BioScience.)
If transgenes have introgressed into land races of maize in Mexico, where did the transgenic material come from since it was until very recently illegal to grow genetically modified corn in Mexico (the ban covered even experimental plantings of GMO corn -- and it was lifted AFTER the possible contamination was reported)? No one is sure, but probably either from transgenic corn that was grown there before the ban, or from illegally planted corn. -- or, probably most likely, from corn imported from the US, much of which is GMO corn. Even though it is imported to MX for feed and producing foods, rather than as seed corn, some seed surely escapes (blows out of trucks, for example) or is saved by farmers and planted. Because the US is not required to segregate GMO from non-GMO corn, there is much potential for inadvertent introduction of GMO corn this way, and then for subsequent movement of its genes by pollen.
Further, some scientists are concerned that the transplanted genes may be unstable, such that the inserted fragment breaks into chunks, which get inserted in various places in the genome. There are particular concerns about the promoter sequence (which is included in the transgenic crop to "turn on" the newly inserted genes). Gene action depends on where it is in the genome, so if a promoter gets stuck in somewhere, who knows what genes it could turn on….The spread of the promoter could turn out to be worse than the spread of a gene for, say, herbicide or insect resistance.
Herbicide resistance :
An increasing number of crop varieties have been engineered to tolerate herbicides, particularly glyphosate (the active ingredient in Roundup).
Side note about this engineering: Glyphosate acts by inhibiting an enzyme that is required for the manufacture of three amino acids, which plants need to make key metabolites. The gene for resistance to glyphosate (derived from a bacterium!) enables the synthesis of these amino acids via a pathway that doesn't require that enzyme, and hence plants can tolerate exposure to the herbicide. [Science 25 May '07]
As of 2011, about 95% of US soybean acreage was planted with beans that were engineered in this way. By 2006, 80% of the global total of GMO acreage was engineered for herbicide resistance [ibid.]. While use of such plants can make life easier for farmers -- and seems to encourage use of conservation tillage, since weed control via herbicides might be simplified when growing herbicide-resistant crops -- there are concerns associated with use of these plants as well. One concern involves indirect non-target effects that may influence monarch butterflies. The larvae of these butterflies depend in summer on milkweed -- it is their obligate larval host (they eat only milkweed). Populations of monarchs have decreased by ~ 50% in recent years, coinciding with the planting of herbicide resistant crops, such as soybeans. Milkweed is a plant that is hard to control by tilling, but it is sensitive to glyphosate herbicides, so its abundance has been reduced in recent years. The butterflies are also challenged by deforestation in their wintering grounds in Mexico, however; the decline in their populations cannot be attributed clearly to the expanded use of herbicide resistant crops and the consequent increase in use of glyphosate. Concern about these genes escaping to weeds (weeds that are closely related to the crop plant -- the genes would move, primarily, in pollen) is quite real! -- and, obviously, herbicide-resistant weeds are not desirable from the farmer's perspective. Not only might the genes escape to weeds, but they may also escape to (and contaminate) non-GMO varieties of the same crop. Some crops, such as cotton, are self-fertilizing, in which case this isn’t a concern, but many others are NOT self-pollinating. Those that are wind-pollinated are particularly of concern, since that pollen can move very readily from one area to another. While it was thought, initially, that there was little movement of pollen from crop plants to weedy relatives, studies using marker genes have now demonstrated that this movement is more common than had been anticipated, validating concerns about the development of herbicide resistant super-weeds.
A recent example involves the perennial grass, "creeping bent grass" (Agrostis stolonifera), which is widely planted on golf courses. An herbicide resistant variety of this crop was engineered and planted in experimental plots in eastern OR, far from any local populations of the grass (in an effort to minimize the risk of pollination of non-GMO plants by the GMO plants). However, studies overseen by the Corvallis branch of the Federal EPA lab used "sentinel plants" to assess how far pollen could actually move. These were non-GMO creeping bent grass plants, planted in pots and placed at varying distances from the experimental plots. Their seed was then harvested, grown up, and the resulting plants tested for herbicide resistance. To their horror, the herbicide resistant trait showed up in plants located as far away as 13 miles from the test plots!! (They confirmed the existence of the genes in these plants not only by assessing their herbicide resistance, but also by analysing them for the protein that the gene encodes and also for the DNA itself.) This is very scary -- creeping bent grass hybridizes readily with many other native and nonnative grass species....you can see the picture.....
>GM bent grass was also found growing wild in a field near the former test plots near Madras, OR. This "gene jailbreak" apparently occured when the experimental bent grass had been swathed and left to dry in the field before harvest and a wind storm swept many of the seeds away. The research company was orderd to find and eliminate all of the rogue plants, but this was impossible to accomplish. OSU's Dr. Carol Mallory-Smith, who has worked a great deal on issues related to confinment, or lack thereof, of GMO genes, was quoted in Science [8 april 2011] as saying, "When you put them out there, you have to accept the fact that you're not going to contain them; you're not going to retract all the genes."
In addition, the genes from the GMO creeping bentgrass were find in wild populations of bent grass several miles away from the GMO field trial plot -- including three natural populations of grass species from the same genus (Agrostis), but that were different species than the engineered species (BioScience Jan. 08). Farmers in eastern Oregon also reported the existance of grasses in ditches that were resistant to Roundup, and, upon testing, these were found to contain the gene. Studies that allow scientists to determine movement of genes from GMO crops, such as this case study involves, depend, of course, on scientists having access to information on the genetic makeup of the GMO crop, which could then be tracked using molecular tools. All too often, however, the information is proprietary, and the developers of transgenic organisms have no legal obligation to provide it to researchers -- which obviously interferes with the progress of understanding potential consequences of GMO field deployment (op. cit.)
As an aside, at least allegedly, allowing decreased herbicide use was a goal when scientists first began to make herbicide-resistant crops. Seem paradoxical? The idea was that growers could use just one rather heavy herbicide application per season, when they were planting herbicide resistant crops, rather than the more commonly used series of applications of several different herbicides over the season, potentially decreasing total herbicide use. However, most current data suggests that herbicide use in general increases when herbicide resistant crops are planted. (Perhaps not surprising, since in some cases the same corporation that developed the herbicide-tolerant crop and sells its seeds also developed and sells the herbicide to which the crop is resistant…..) Further, there is concern that use of one herbicide (the one that the crop is engineered to tolerate) will speed acquisition of resistance to that herbicide on the part of weeds, since the selective pressure towards resistance is coming from only one type of herbicide. This may be particularly unfortunate in the case of "Roundup-ready" crops, engineered to tolerate glyphosate, as that herbicide is relatively benign compared to many other herbicides; it breaks down relatively quickly, and has relatively low mammalian toxicity compared to some.
Huge controversies have stormed in the Willamette Valley in recent years over the planting of herbicide-resistant GMO sugar beets (approximately half of the US sugar crop comes from Roundup-Ready sugar beets, and about half of the sugar beet seed produced in the US is grown here in the Willamette Valley...), alfalfa, and canola. Several organic growers in the Valley raise table beets for seed, and sugar beets readily hybridize with these, as they also do with chard. The USDA had approved planting of GMO sugar beets here in 2009, and crops were planted, but a Federal judge overturned that decision, and ordered USDA APHIS to do an Environmental Impact Statement. In the ruling, the judge wrote that planting GMO sugar beets here could potentially eliminate farmers' choice to grow non GMO crops or consumers' choice to eat non-genetically engineered food. In fact, sugar beet seedlings showed up in top soil being sold at a garden store in Corvallis, these were tested, and were found to be Roundup-resistant; they were "on the move!" [Science 8 April 2011]. However, in summer 2012, USDA-APHIS, having completed the Environmental Impact Statement, announced its decision to deregulate the planting of GMO sugar beets entirely.
Another issue affecting producers of vegetable seed here in the Willamette Valley, organic and otherwise, has been a move to plant canola here. Canola is widely grown in many areas of the US, but, so far, not significantly in western Oregon. Some growers here, however are eager to plant it as a rotation crop, and also for its seed, which can be used to produce biofuels. Canola, however, readily crosses with other brassicas, such as broccoli and brussells sprouts, which are grown here not only for selling for people to eat, but also for seed -- much of it organic, and exported worldwide. The climate here is ideal for growing such crops. As of 2011, no one but researchers were allowed to grow canola here in the valley, but Oregon Department of Agriculture issued a temporary rule in of 2012, loosening the ban on its planting here. This rule was challenged by a variety of farm and food groups, and the Oregon Court of Appeals issued a stay on the ruling, meaning that, as of this writing (late November 2012), canola cannot be planted commercially in the Willamette Valley.
Yet another GMO crop issue has been controversial in the Willamette Valley and nationally, recently. This crop is alfalfa. Farmers who sell organic alfalfa hay to dairies and who export hay to other nations have grave concerns about their crop being contaminated by herbicide-resistant GMO alfalfa. A ruling in 2007 ordered that GMO alfalfa could not be planted until adequate Environmental Impact Statements were completed. This ban was lifted in 2010, by the US Supreme Court, however, and GMO alfalfa can now be planted without restrictions [Science 4 Feb 2011]. While some claim that there is little potential for it to cross pollinate traditional alfalfa because the hay is "mostly" harvested before there is "significant" blooming by the plants, the words in quotation marks are important...
The fact that GMO material can move around more readily than anticipated -- either by pollen or by inadvertent spread of seed (blowing off trucks after harvest, for example) rasies a several nasty legal issues, including one about "stolen patented material." While some crops are primarily self-pollinating, many are not; one plant must be pollinated by another plant. Even crops, such as rice, that are primarily self-pollinating do occasionally outcross (get pollinated by another plant). In the case of rice, it has been demonstrated that genes from a variety engineered for herbicide resistance moved from the small-scale test plots on which the rice was being grown to other rice plants in the area, including some that were the original stock of a commercially available variety ("foundation stock;" Science 22 Sept. '06)
As just one (famous) example, a canola farmer in Canada was sued by Monsanto because they found some genetically engineered canola growing in his fields, when he wasn't a purchaser. They claimed that he stole it. However, he claimed that that would be the last thing he'd do -- he claimed that the GMO canola had, in fact, contaminated varieties that he had been developing for 53 years. He was a "seed saver" - that is planted his own seed each year. The material could have reached his field though seed blowing from a truck, by birds, or simply by cross pollination with his crop. (Monsanto's claim that he "stole" the material, which, was upheld by the courts, seems to me to be analogous to my dumping my belongings in my neighbor's yard and then having my neighbor arrested for burglary.) Monsanto claimed, in this case, that, if his crop was inadvertently pollinated by GMO canola -- or if he collected seed from canola that sprouted near his fields and that came from wind-blown material off harvest trucks and then grew that out -- his plants are stolen Monsanto property. The polluter doesn't pay, it is the person who receives the pollution who does. (In this case, he was found guilty, but did not have to pay fines.) Companies that produce GMO crop varieties have now been successful in several similar law suits. Easy movement of GMO genetic material also raises concern for organic farmers. An organic grower who farms near a GMO-using farmer could risk not only such law suits, but could also risk losing his/her organic certification if his/her plants were found to contain GMO constituents (since the new "organic" label in the US excludes use of GMO materials).
Resistance to herbicide can develop in weeds via the natural selection pressure imposed by the exclusive use of only one herbicide as well -- that is, weeds can develop that resistance without being pollinated by GMO pollen from a crop. Indeed, this seems to be happening in the case of glyphosate herbicide [Science 25 May '07]. It will be unfortunate if this resistance becomes widespread because, as herbicides go, glyphosate is considered relatively benign -- for example, it has low toxicity to mammals and insects and breaks down relatively rapidly. In addition, some fear that if it becomes ineffective, farmers will return to relying on tillage to control weeds with consequences for soil erosion (although there are other ways to control weeds too!). In attempts to control or slow the acquisition of herbicide resistance in weeds, the following strategies are starting to be employed or are being investigated: (1) rotate crops, using a crop that doesn't require treatment with the herbicide in the "off years," (analogous to not using the same antibiotic all the time to control human diseases); (2) use a variety of herbicides rather than just the one the crop is engineered to resist; (3) develop crops that can resist even higher doses of the herbicide -- doses that hopefully will kill even resistant weeds [this, of course, steepens the strength of the selective pressure for resistance in the weeds! -- here goes another "evolutionary arms race!?"]; and (4) develop crops that are resistant to other herbicides or to more than one herbicide. (One is intriguing -- the resistance gene is expressed in the chloroplast and thus will not move with pollen, since chloroplast DNA is inherited only maternally. This would certainly decrease the risk of inadvertent pollination of non-GMO crops or weeds by GMO pollen!]
Sterile plants ("terminator" varieties)
Varieties of rice and soy have been engineered to produce sterile seeds. This, of course, would make it necessary for growers to buy seed from the seed companies each year, rather than saving seed for replanting, and, in the view of many, is unethical on the part of the seed producers. Being forced to buy seed each year is, of course, particularly problematic for poor farmers in many lesser developed countries. This issue points up another concern about genetically-engineered crops. Most of the research on these crops is being conducted by giant agro-companies, who are motivated more by profit rather than by concerns about improving prospects for agriculture and food supplies. Should they be the central figures in this research, or should the research be sponsored by the government, and conducted by researchers who aren't motivated by profit and perhaps questionable ethics? A debate. In addtion, there are concerns about the genes for steritility moving to native, desirable plant species, rendering them sterile as well. In response to public outcry against these "terminator" varieties, however, most companies who were involved in their development agreed to cease this work.
GMO's with human nutrition or ability to tolerate stresses as a focus:
Some research is focusing on using genetic engineering to develop crop varieties that can tolerate stresses, such as flooding, saline soils, and drought. In some cases, corporations have even made agreements to furnish seed free to small farmers in poor areas (Science 11 Apr. 08). However, so far, relatively little progress has been made in these areas, compared to that made in engineering pesticidal or herbicide resistant crops. Engineering to enhance stress tolerance is complex, as the plant's fundamental physiology is often involved. Engineering for stress tolerance could expand food-producing capabilities in agriculture. This would be wonderful, in many ways, however concerns about the movement of genes from these plants to weeds via pollen are valid – do we want, unintentionally, to produce weeds that are better able to tolerate these stresses? Not only could this make the weeds more problematic in agriculture, but it could make them better able to compete with native plant species, changing the species composition of ecosystems over time.
Human nutrition hasn’t been a major focus of engineering in crop plants, lip-service to the contrary. For example, most GMO’s now being planted commercially have been engineered to resist either pests or herbicides, with lesser acreage’s devoted to crops engineered for characteristics such as enhanced frost tolerance or nutrional values. However work is on-going to "biofortify" numerous crop varieties with constituents ranging from enhanced protein content to added Vitamin content. You may have heard excitement (and controversy) about a new rice germplasm that was recently developed "Golden Rice?" This rice is nutritionally enriched with a precursor to Vitamin A, which is essential but lacking in the diets of many people. As you know, rice is a staple part of the diet of billions of people in the world, but it is lacking in beta-carotene (or other pro-vitamin A compounds), which is a building block (a precursor)for Vitamin A synthesis in the human body. (That is, it doesn’t produce beta carotene in the starchy part of the grain that is eaten; only in external rice tissues is it produced.) As a result, millions of people suffer from Vitamin A deficiency, which can lead to decreased resistance to infectious diseases and to blindness (xerophthalmia). At least 400 million people, globally, are estimated to suffer to some degree from vitamin A deficiency symptoms, with about 500,000 people going blind from it each year and about thousands dying each year. "Golden rice" has been engineered to address this deficiency, using genes from daffodils and a bacterium (and with genes from maize [corn] and a bacterium). This rice produces beta-carotene (vitamin A precursors), which can then be used by the human body to produce Vitamin A.
A brief note on technique: The genes for beta carotene synthesis, along with a promoter (segment of DNA that activates genes) were inserted into plasmids (small loops of DNA) that occur inside the bacterium Agrobacterium tumefaciens, and the bacteria with these plasmids were then added to petri dishes containing rice embryos. The bacteria infected the embryos and transferred to them the genes that encode the production of beta-carotene. This transgenic rice can then be crossed with traditional rice varieties, conferring on them the ability to produce beta carotene, enhancing the nutritional quality of the rice.
The scientists who developed this transgenic rice intended to make it available free of charge to rice breeders in lesser developed nations, so that they could incorporate the genes into local rice varieties and pass the benefits along to local farmers. However, efforts to do this have been stymied, largely by legal issues involving regulations over field trials and commercial release of GMO's. Regulators believe that they must apply their regulatory standards uniformly across GMO crops, even in cases like this one, where it is very difficult to imagine adverse consequences from planting the material. In fall of 2005, I heard the lead scientist on the creation of glden rice speak, and he was very frustrated that thousands of people continue to go blind, die, and otherwise suffer every day owing to regulatory hold-ups. I could see his point, but on the other hand, perhaps uniform regulatory standards are necessary??? Time will tell the outcome.
(As of 2008, the International Rice Research Institute (IRRI) has golden rice in a field trial, the first since it was developed in 1999, and it is anticipated that trials in farm fields in Bangladesh could start in about 2 years [Science 18 July 2008]. The most opptimistic scenarios predict that it will first be planted by farmers in 2011 [Science 25 Apr. 08]). A furor broke out recently over a US-funded study in which Chinese children were fed either golden rice, spinach, or capsules containing B-carotene in oil to assess how readily the B-carotene from the golden rice was converted into Vitamin A. Researchers reported that the conversion from rice was as efficient as from the capsules, however the study caused a huge controversy, which claimed that the children had been used as guinea pigs [Science 14 Sept 2012]; clearly, this is an emotionally charged issue!
Now, think how you felt when you read about this "golden rice." Did you find yourself thinking, "Geeze, people ought to be able to plant this out withour going through all the regulatory red tape!"? But in other aspects of GMO’s, do you find yourself resisting their use and development? I think it is useful for each of us to examine our responses to GMO’s and try to evaluate the consistencies or inconsistencies in our responses, and the reasons for them….How do we sort out the potential benefits of GMO’s (as perhaps illustrated by this rice) versus the potential hazards (ecological, human-health, or social) associated with them? How on earth does one assess the likelihood of unanticipated consequences -- seems almost impossible, doesn't it? The answers, in my view, are not straight forward! Potential benefits are real, as are potential risks, and again we should remember to be careful to distinguish our responses to the techniques used to produce the traits versus characteristics of the traits themselves.
Research is currently underway to biofortify maize, which does naturally produce the Vitamin A precursors alpha-carotene, B-carotene, and B-cryptoxanthin. This development would involve marker-assisted selection, as desribed near the top of this section of notes, hence the maize would not be trans-genic, as is the corn. This would probably make it easier for the corn to be commercially grown relative to golden rice. [Science 18 Jan 2008].
Crops that make pharmaceuticals or compounds useful to industry
There is a good bit of interest in engineering "pharma crops" -- plants that will make pharmaceuticals usful to humans. The hope is that these will allow drug costs to decrease or that they will allow the manufacture of compounds that are otherwise unavailable. One example is a corn variety that has been engineered to contain a human gene that produces an antibody (proteins that white blood cells use to defend the body) to genital herpes, so that it makes the antibody which could then be used as a treatment in humans. This demonstrates one utility of the human genome being sequenced - the sequences allow scientists to find particular genes more readily. Food crops have also been engineered to produce veterinary drugs, plastics, hormones, and detergents.
As of 2003, there were > 300 trials of biopharm crops going on in the US - and open air field trials in 14 states (as of 2003; I've also read 35 states [Union of Concerned Sci'entists "Catalyst" Spring '07]. Many of these involve human antibodies, and all (I believe) are using food crops to produce the compounds. Trials include rice, corn, tomato, potato, tobacco, rice and probably other crops as well.
The FDA hasn't yet (as of 2008) approved any pharma crop chemicals for use as human drugs (none have completed final clinical trials, as of 2008), but several "pharmed protenis"' are close to or on the market, including a vaccine purification antibody (Science 25 April 08).
While it seems that there is a lot of potential for these crops to reduce drug costs, many question the sense in using FOOD crops for this!! Such use opens many possibilities for food supplies being contaminated by crops that contain pharmaceuticals -- inadvertently, or deliberately in the case of a terrorist action. To date (2007) most of this work uses corn [> 2/3 of trials use it], because its genetics are well understood, it is easy to grow in many places, and dried seed can be stored for a long time with the pharmaceutical compounds intact. Several groups, including the Union of Concerned Scientists, are working towards legislation that would ban use of food crops for this work. In fact, concerns about "pharm crops" have been vociferous enough that some major corporations have backed off entirely on efforts to develope such crops.
As an example of the possible hazards, seed from corn that had been engineered to produce a pig vaccine sprouted in soybeans that were planted the next year on the same field ("volunteer" corn plants). Seed from that corn was accidentally harvested along with the soy and mixed with soybeans at a grain elevator, but somehow the contamination was discovered before the soy was sold -- 500,000 bushels of the soy were then destroyed ((Catalyst spring 07; Science 25 Apr 08; see also your assigned reading, "Can crop transgenes be kept on a leash").
One potential solution is to "raise" the pharmaceutical "plants" under conditions of complete confinement. For example, carrot tissue cultures grown in plastic bags, duckweed grown as a layer in clear plastic bags, and algae grown in factories are being tested as producers of some pharmaceuticals and other products. Some companies have, in fact, completely backed off from working with food crops engineered to produce medicines or other commercial products, sensing that there are tremendous logistic, legal and ethical issues involved.
Crops are also being engineered to produce compounds useful in industry - for making plastics, trees with lignin that is easier to pulp or convert to biofuels, and so forth. The same concerns mentioned just above apply to these crops as well, of course.
HOW ARE TRANSGENIC OR OTHERWISE GENETICALLY-ENGINEERED CROPS AND BIOCONTROL AGENTS REGULATED?
There is some confusion here. FDA regulates foods, but it suggests that crops genetically engineered for pest resistance should be regulated as pesticides rather than as foods. On the other hand, EPA regulates pesticides, but sees these crops as foods. In general, however, it seems that FDA regulates these crops when it is convinced that the crop contains some product that is new to the human diet or characteristics that might make it suspect (as an allergen or toxin, for example). The USDA and EPA jointly regulate the testing and release of genetically-engineered crops (and other creatures), with their concern focusing more on the process used to produce the crop (that is, the engineering) than on the result....
APHIS [the Animal and Plant Health Inspection Service] is the division within the USDA that regulates development, testing, and use of transgenic crops and biocontrol agents. They try to weigh costs and benefits, but, as you can imagine, hard numbers are difficult to come by! Witness the uproar in 1999 over a report that a potato that had been engineered to produce a pest-deterring lectin, caused immune system suppression and slowed growth in rats fed these potatoes as compared to those fed "regular" potatoes. The report was discredited, then vindicated, and then discredited again -- just one example of how difficult it can be to test for and demonstrate risks!
Formal rules for determining the safety of releasing genetically engineered pest controls have not yet been developed. An example of the types of questions that can arise follows. As you know, conventional insecticides often kill beneficial predatory insects as well as the target insects. An insecticide used to control several insects in CA almond orchards is highly toxic to predatory mites that prey on harmful spider mites, but not particularly toxic to the spider mites. With its use, then, growers often see a boom in spider mites. One solution has been to produce, through genetic engineering, a predatory mite that is resistant to the insecticides. Sounds fine, but consider the following questions:
(1) How far will the genetically engineered mite move and what are the consequences of it being widespread? No one knows. (Scientists have put a genetic marker in it so that they can track its dispersal.)
(2) What if this predatory mite develops a taste for a nontarget herbivore that is an effective controller of some particular weed species?
(3) What potential exists for transfer of the foreign gene to other arthropod species? "Jumping genes" are likely facilitators of such cross-species transfers.
LEGAL, REGULATORY AND TREATY ISSUES
During 2000, delegates from some 130 nations met more than once and hammered out a treaty governing some aspects of trade involving GMO’s (treaty variously referred to as "Biosafety protocol or "Cartagena Protocol").The treaty became binding in 2003, following its ratification by at least 50 of the signatories. While the US participated in deliberations, it was not a party to the protocol, because it hadn’t ratified the enabling convention at the Rio Earth Summit in 1992, so is not cound by provisions of the treaty.
The treaty provisions focus largely on living GMO’s, such as seeds or fish, that could potentially colonize new areas. It set up a clearing house (database) for information on how they were created and tested, which is maintained by the UN. With regard to labeling, it indicates that export products intended for food or feed must be labelled "may contain GMO’s" unless they are certified to be GMO-free. It does not require exporters to segregate GMO-containing products from traditional products. Regarding importation of GMO’s or material derived in part from GMO’s, the treaty allows nations to unilaterally refuse to import GMO’s based on suspected ecological, health, or social risks – ie.e., those do not have to be proven for a nation to reject imports.
While many nations do have mandatory labeling for foods containing products derived from GMO’s (despite initial resistance from the US via the WTO; Consumer Reports.org July 5, 2011) the US does not. Bills regarding labeling and safety-testing of GMO materials have, however, been introduced in both houses of the US Congress during recent years. These issues (testing and labeling) are quite complicated here in the US, in part because several different Federal agencies have jurisdiction over various GMO organisms and products. For example, FDA is in charge of most aspects of food safety issues, but EPA regulates pesticides and the USDA oversees much of the field testing of GMO’s. Since many GMO crops are engineered either for pest or herbicide resistance, EPA becomes involved in their testing and regulation.
In 1992, the FDA declared that if ingredients derived from biotechnology did not "materially alter" food, they didn’t need to be labeled specifically. That is, their argument was that compounds produced by, say plants, that the plants were induced to produce because of inserted genes were not materially different than those compounds produced by plants that normally produce them. However, in the fall of 2000, bowing in part to public pressure and to concerns about the potential for adverse human health effects to result from GMO-derived foods (e.g., foods to contain allergens that people didn’t expect to be in a particular food product), FDA announced that it would issue guidelines for voluntary labelling of foods that contain products of biotechnology. As far as I know, this has not yet happened, other than the Non-GMO label described above.
FDA also proposed new rules concerning safety testing of GMO-derived products. In the past, FDA had maintained that such testing was not generally necessary because the products’ compositions did not differ materially from similar products that were produced without use of biotechnology. That is, it argued that testing (and labeling) should be based on composition of the products, not on the method of manufacture. For example, testing for safety is not generally required for products that result from conventional plant breeding. FDA feels that, as a class, bioengineered foods can’t be distinguished compositionally from those produced by conventional breeding. However, if bioengineering results in a "material difference" – that is, introduction of an allergen, toxin, or novel compound, then additional testing and labeling would be required. In fact, FDA recently (2000) did require labeling of bioengineered soy and canola oils, because they contain an altered fatty acid composition.
By FDA’s new rules, rather than requiring mandatory safety testing of all food products that involve bioengineered compounds, companies would have to publicly disclose their new biotechnology crops before planting them out, and would have to notify FDA of their plans to sell bioengineered foods at least 120 days pre-market. The manufacturers would also be required to make testing and safety results available to FDA, along with any other relevant information, so that FDA could review the data and determine whether additional regulatory steps need to be taken (e.g., will the bioengineerd food simply contain products that are already generally recognized as safe [but simply result in this product from a bioengineered method of manufacture] or will it contain compounds considered to be new food "additives," in which case additional testing would be required).
A question, however: is it always certain exactly which genes have been inserted and what their roles will be? In addition to the gene promoter issue mentioned above (with the Mexican corn story), and concerns about "position effects" ( a gene's action can depend on where in the genome it gets insereted -- who its neighbors are) apparently sometimes additional genetic material is inadvertently included when the genes are spliced into the recipient, and who knows what it is or does. The research simply hasn't been done to assess these risks, and there is also a lot that we don't understand about gene expression. These concerns, in my view, warrant caution!
The National Research Council was asked to review the procedures in place for testing and regulation of GMO's in agriculture, and released their report in 2002. Environmental hazards of GMO's were top on the NRC's list of concerns about GMO's, followed by threats to human health from allergic reactions to foods and risks from xenotransplantation (placement of organs from GM animals into humans - as in pigs, which carry about 50 retroviruses in their genome which could become pathogenic and contagious in a human host). Given that environmental hazards were considered to be most serious, the National Reseach Council suggested that the FDA is not, at present capable of making wise decisions about testing and release of GMO's because the FDA basically lacks relevant in-house experience; it is not staffed by ecologists and others who really should be making these decisions.
With regard to products derived from plants that have been engineered to resist pests (e.g., that produce the Bt toxin), EPA has particular responsibility (since Bt is an insecticide and EPA regulates pesticides). EPA has generally maintained that new testing of the products is unnecessary, since the products were tested separately from their inclusion in foods when they were first approved for use as pesticides (e.g., Bt sprays). Further, it is not mandatory in the US that foods be labeled as to whether any of their ingredients were treated with pesticides, hence the legal argument goes that such labeling is not necessary for foods that contain the pesticidal compounds as bioengineered constituents. Tough legal questions!
USDA is responsible for setting standards governing use of the label "organically grown" and new standards for that label went into effect in 2001-2002. The new standards exclude from such labeling foods that contain genetically-engineered materials, although, as described above, it is increasingly acknowledged that "genetic pollution" from GMO crops is almost impossible to avoid, such that the "organic" label does not necessarily mean ZERO GMO constitutents. How can an organic grower protect him or herself against "genetic pollution" in the form of pollen from a neighbor's GMO crop?
USDA must approve field testing of new GMO’s, and, just for your information, in 1998, the USDA issued 102 permits for field testing of GMO-plants in Oregon alone, ranging from wheat to sugar beets. (The case of the creeping bent grass pollen movement described above -- in the section on herbicide resistant GMO's, above, looks as if it might provoke a serious re-evaluation of the adequacy of USDA's procedures regarding allowable field testing procedures. In fact, in winter 2007, a US District Court ruled that USDA did not properly regulate field trials of this genetically engineered grass. The ruling was critical of procedures that USDA used to determine whether or not an environmental risk assessment is required before planting. I don't know what the specific consequences of this ruling are.
So, as it stands now for the US, labeling of foods that contain GMO-derived materials is NOT mandatory, unless they contain constituents that are "materially altered" compared to constituents "normally recognized as safe. " This may change, of course, as new information becomes available or as public pressure/ perceptions change. Present polls of the public in the US suggest that a large majority of Americans do want to know whether foods they eat contain GMO-derived products (and it is estimated that, currently, about 70% of processed foods contain ingredients derived from transgenic corn, soy or other sources). In fact, public pressures against GMO-products in food have become intense enough that Gerber renounced the use of transgenic products in its foods, McDonald’s (and some other fast food chains) has foresworn use of genetically engineered potatoes, and Frito-lay declared that it will not use GMO corn in its products. (These have, of course, resulted from consumers expressing concerns about these products -- clearly, consumer pressure has power!) In the spring of 2001, Monsanto dropped its Newleaf potato from US and Canadian markets after McDonalds cut orders for the GM potatoes. This was a Bt potato, containing toxins effective against the Colorado potato beetle. Other fast food chains also refused, because of consumer demands, to buy this potato.
In the face of such pressures and concerns, why not label? There are several reasons, some of which relate to legality of doing so, some of which relate to corporate pressures against labeling, and some of which relate to the fact that actual dangers to humans of consuming foods containing genetically-engineered products has not been reliably demonstrated to-date (excepting those that express known human allergens, such as derived from Brazil nut oils or peanuts). The National Academy of Science’s research arm (the National Research Council) released a major report on GMO issues in the year 2000, in which they concluded that there is as yet no evidence that gene-altered foods are unsafe from a human health perspective (excepting known allergens). They also urged that there be continued and thorough investigation of possible human health effects. This report also suggested that the the US government should do a better job of testing and regulating crops modified to resist pests. (In fact, it would be difficult to certify many foods as GMO-free, because of pollen drift between GMO and nearby non GMO crops.....)
REGULATION THAT ATTEMPS TO DELAY DEVELOPMENT OF PEST RESISTANCE TO ENGINEERED PESTICIDES
As we've seen, many of the GMO crops that are cultivated over the widest acreage are engineered for resistance to insect or other crop pests. Part of the motivation for developing these crops is that their use could allow use of externally applied synthetic pesticides to diminish, which is a noble goal. One recent example involves the manipulation of a gene that seems to enhance plant’s natural defense systems against pests and predators, and that researchers hope could speed elimination of the soil sterilant, methyl bromide (a bad one for depleting stratospheric ozone) from use in agriculture. As another recent example (described briefly above, in the section on crops engineered for insect or disease resistance, the corn rootworm complex (comprised of three beetle species) infects most corn-growing land in the US, and the complex is generally treated using insecticides (or crop rotation). Pesticide treatment for this pest complex alone comprised about 1/5 of all the money spent on insecticides used on all crops in the US – it is a big deal! Monsanto has created a new bioengineered corn that contains toxins effective against this complex (also derived from Bt). Its use could decrease insecticide use in corn production. BUT, it hasn’t been demonstrated to be non-toxic to beneficial beetles, its longevity in the soil is unknown, and resistance to it by the corn borer insects seems virtually certain to develop, as they eat little besides corn roots.
EPA does require people who grow such transgenic pest-resistant crops to develop "resistance management plans," but the development of resistance by pests to the compounds remains a concern. Pests are exposed continuously to the pesticides when the crops themselves produce them, which strengthens the selective pressure favoring resistant pests. This is particularly worrisome in the case of Bt-toxins, which have been used successfully for years, and without major resistance problems, owing partly to the conservative fashion in which they’ve been used (in part resulting from the fact that it has only been used when insects are causing problems, not in a "preventive" fashion, which characterizes the Bt-engineered crops – kind of like taking antibiotics all the time just in case you happen to get infected with a bacterial disease!).
Part of a "resistance management plan" often involves creating refugia for pests, oddly enough. The idea is that a field adjacent to a field containing a bioengineered Bt-containing crop would NOT contain the Bt genes, so that susceptible insects could survive there. They would then mate with the resistant insects that survived in the Bt-treated fields, and essentially dilute the resistance. This strategy would be helpful IF growers were willing to essentially sacrifice areas as refugia, and IF resistant pests have the same mating times as the susceptibles (some evidence suggests that resistant insects, in some cases, have either delayed or advanced maturation, which would make them unable to mate with susceptibles…) In fact, EPA requires that corn growers in the US plant at least 20% of their corn acreage with conventionally bred varieties, which would serve as refugia for Bt-susceptible insects. The seed companies who sell seed to the farmers are supposed to be sure that farmers comply with these planting requirements. (A survey in the summer of 2000, howver, indicated that at least 1/3 of the surveyed corn growers did not comply...)
I don't read about this as much as I do about plants, but here is one tidbit related to fish. Salmon have been engineered in various ways including to contain extra copies of a gene encoding growth hormone (These were inserted into Atlantic salmon with the added growth hormone gene coming from Chinook salmon along with a promoter sequence from a different species of fish.) Tilapia have been engineered similarly, by adding a promoter from a virus to increase expression of a native gene that codes for growth hormone. These fish then grow much faster than "normal" fish of their species, and, of course, they eat more. Neither has been approved for commercial use, although, as of early 2012, FDA was poised to approve commercial farming of the Atlantic salmon [Science 19 Nov 2010; UCS Catalyst fall 2011]. These salmon grow twice as fast as native salmon, and, if approved by FDA, would be the first transgenic animal approved for human consumption in the US. If commercial production does begin, and if the fish escape, there are twin grave dangers: that they'll outcompete natives - and breed with them. Allegedly, they all of the females will be sterile, but sterility cannot be 100% guaranteed when it is induced in mass. These fish probably don't create a big concern for human health, because the growth hormone genes, even though transgenic, are from other fish that people eat - and the hormones are destroyed by cooking and digestion; health risks are assessed by comparing the nutritional profile of GMO to non-GMO fish, and screening for known toxins and allergens. Environmental concerns are huge here, though (and there is that promoter to worry about...)
I believe that it is important that we remember that we are tinkering with fundamentals here, and that once a GMO is released into the field (and wider environment), it cannot readily be "re-captured." We must be as sure as we can possibly be that unintended consequences will not result, and should ask ourselves whether we can ever be sure enough....Remember the "precautionary principle?" Here's, in my view, a place to apply it.
The next section of these notes discusses use of chemicals as part of an IPM strategy (click on ">>," below, to jump there now). To return to the list of topics in this unit on sustainable agriculture, click on sustainable; to return to the master Table of Contents for this BI 301 home page, click on "CONTENTS" below. For reminders on how to move about within and among these documents, click "navigate."
This page is maintained by Patricia Muir at Oregon State University. Page last updated Nov. 29, 2012.