Genetically Modified Crops: A Help or Harm?
Marcos Stoltzfus
Biology Senior Seminar
November 30th, 2005
Thesis:
Genetically Modified (GM) crops have several extremely valuable characteristics, yet also have quite a few drawbacks. When considering the unknown implications of introducing such a creation to the natural world, it may become apparent that their use is unwise.
i. Breeding’s history
1. Example- corn
2. Mendel
ii. Distinctions in Methodology
iii. Limitations
i. Ht
ii. Bt
iii. Golden Rice
iv. Other modifications
i. Kudzu vine
ii. Monarch butterfly
iii. super weeds
Imagine a day when food abounds in the world, where none grow hungry. Corn grows 12 feet tall, 5 ears on a stalk. It provides its own fertilizer, pesticides, and has all the essential nutrients in a single kernel. With the marvels of modern day science, such an organism may not be so far off. Such a super-plant may not be solely a thing of the imagination. But consider if you will, what the trade offs may be for such an uber-organism. What unexpected genes have been inserted unintentionally into the juices of this fruit? What expense do we pay for having such a successful plant? What environmental disasters might we be unaware of that are just around the corner?
Genetically Modified (GM) crops are certainly an intriguing and exciting technology that even now is looking forward to unexplored vistas. We have already uncovered a vast array of possibilities, yet much remains to be discovered. As GM crops make their way into a common existence in our world and on our plates, it is essential to know as much as we can about the true nature of these organisms. When considering the unknown implications of introducing such creations into the natural world, it may become apparent that their use is unwise.
History-Where did Genetically Modified Crops come
from?
Genetic modification is a relative newcomer to the science scene, arriving within the last twenty years. Compared to such fields as astronomy, which the ancient Mayan civilization was using centuries ago, the realm of inserting genes into an organism is brand new. In 1983, the first groups to insert foreign genes into a plant announced their success, almost simultaneously. Three groups; from Washington University in St. Louis, The Monsanto Company, and University of Groningen in Belgium all announced on the same day that they had accomplished the feat (Fuller, 2004).
Several of the first discoveries included the use of bacterial antibiotic resistance genes which were spliced into tobacco plants of some kind (Fuller, 2004). Since that time many more advances have been made, and have been much more practical in their applications as well. While these marvels are certainly exciting, we have always been able to ‘design’ plants to some degree using breeding techniques. But what separates Genetic Engineering (GE) and plant breeding?
Breeding vs. Genetic Modification
When discussing genetic modification, it is almost impossible to understand it without looking at its counterpart, plant breeding. Ever since the Agricultural revolution at the dawn of civilization, humans have been modifying their crop plants, applying pressures different from those in the natural world. This is called artificial selection. It involves humans directing the tools of evolution, forcing plants to exhibit traits we deem desirable (Nottingham, 2003, p. 2). This could be as simple as selecting for the healthiest plants that stand tallest, or perhaps those that produce the most fruit. One example of this is the corn plant. Some scientists believe that the ancestor to the modern corn plant is called teosinte. This plant has only a few small ‘ears’ containing only several kernels, and has a much more branched structure to it. The theory suggests that Native Americans may have applied pressures to it to make it more productive (more kernels/ear), and easier to harvest (one stalk vs. many) through artificial selection. This seems to be true, since these two organisms have been examined genetically, and found to be cousins (Corn and Its Untamed Cousins, 2005). This is just one example of how humans have applied artificial selection to plants; to tailor them to fit our needs. Although humans have been doing this for centuries, one of the first individuals to explore this area scientifically was Gregor Mendel.
Mendel
is often considered to be the father of genetics because of the work he did
studying heritability in pea plants.
Mendel was a monk at the Augustinian monastery of
An important characteristic of breeding is that it occurs using the same methods as those found in nature. Using sexual reproduction, plants with desirable traits can be crossed, in an effort to find offspring with the same traits, or a useful combination of traits. In essence, this puts limitations on breeders concerning what crosses may be done. Biological principles of diversity dictates that only related organisms may breed with each other successfully. Several species of wheat may be able to interbreed, but may not exchange pollen with a banana tree resulting in viable offspring. Using the methods developed by nature, this is simply not possible.
Genetic modification ignores these barriers through the use of methods not available in nature. While breeding is limited to only organisms very closely related to one another, GM allows even barriers at the kingdom level to be overcome. In a rather dramatic example, the gene coding for bioluminescence in fireflies was transferred to a tobacco plant, resulting in a plant glowing much as the common beetle (Sengbusch, 2003).
Clearly in nature this kind of a cross would never be possible. Simply put, the gene’s forms would be remarkably incompatible, not to mention the sexual structures of both the plant and the beetle. The genes would not be accepted, and would never result in the light-giving plant that was attained in the laboratory. This is a key difference between breeding and GM. Genetic modification is defined as the splicing of genes into an organism that would normally be outside the organism’s natural reproductive process (Genetic Engineering, 2005). But if the introduction of new genes cannot be done using natural methods, how do scientists accomplish this act?
Vectors of Genetic Modification
Despite the fact that inter-kingdom breeding cannot occur naturally, there exists several examples of inter-kingdom gene transfer. This is usually done at the microscopic level, by bacteria or viruses. One commonly used vector is the use of the Agrobacterium bacteria. This is a bacterium that causes crown-gall disease in plants by transferring a plasmid into the plant cells, causing a phenotypic change at the source: a gall (Fowler, Scott and Slater 2003, p.56). Scientists have been able to utilize this phenomenon by having Agrobacterium carry and insert a desired gene into the plant. For example, the luciferase-producing gene. By making cuttings and growing tissue cultures, the plants that have successfully taken in the gene can then be grown into new parent plants.
Similarly, viruses can be used to inoculate genes into plants. Viruses normally reproduce by inserting their own genes into a host cell, which turns the cell into a virus making factory. By changing the genes the virus inserts to genes we’d like to see exhibited in the plant, we can successfully introduce new DNA into the target organism. Each type of virus has a set of specifications as to which plant it can interact with, according to the type of plant it infects in nature. Some examples of transformation viruses are Brome Mosaic virus, caulimoviruses, and Gemini viruses. Each is specific according to the range of hosts and the type of DNA it uses to infect (Walden, 1989 pp. 49-67). These are two biological vectors, but scientists have another way to introduce new genetic material as well.
The other vector is the gene gun. In simplified terms, this process involves taking many microscopic gold particles and covering them in the desired DNA. These particles are then shot at high velocity at plant cells. The DNA strands on the particles that land in the nucleus dissolve off, and inserts itself into the plant genome (Fuller, 2004). Afterwards, similar to the bacterial and viral vectors, plant tissues are grown, and watched to see which exhibit the trait.
Possibilities and Realities of Genetic Modification
As touched on above, the theoretical possibilities for GM seem almost endless. Like the glowing tobacco plant, it seems there is a startling potential of what could be implemented with the tools of GM at our disposal. Reality dictates, however, that a great many of these are not practical, and therefore will not be explored. The tobacco plant example, while interesting, and imagination-sparking, does not appear to have a great deal of sensible functions. While we can do many things, only a few have actually been put into place on a large scale. Most of the widespread modifications in use now are specifically designed for our modern agricultural model. They aim to increase yields, and are adapted to modern farms. Two of the most prevalent are herbicide tolerance and insect resistance.
Nottingham (2003, p. 37) states that “herbicide resistance
is the characteristic most commonly engineered into transgenic crop varieties
grown in field trials.” This trait can
be extremely helpful to farmers in increasing effectiveness of crop growing.
The basic idea of herbicide tolerance (Ht) is this. When growing crops in a monocultural
system (as in most
The second most common modification is that of pest resistance. One of the major problems farmers face aside from weeds, are the predation of animals on their crops. This is mostly done by insects, specifically the orders Coleoptera (beetles) and Lepidoptera (butterflies and moths). Consequently, GM plants have been developed to combat this problem.
Pesticides
have been developed and used for a great number of years that include a
naturally formed crystal from a common soil bacterium, Bacillus
thuringiensis (Bt). This
bacteria forms a crystal spore that is deadly to
Lepidoptera larvae (caterpillars).
Sprays including this spore are widespread, and have been in use since
1920 (Chein n.d.).
After the dawn of GM, some industrious scientists incorporated the gene
encoding the Bt producing protein into plants, thereby allowing them to produce
their very own pesticide (Fuller, 2004).
Clearly, if a plant can produce its own pesticide, farmers will not need
to use pesticides as frequently.
There are a number of
other modifications that are either in development or in use currently, but
none are quite as prevalent as Ht or Bt.
One of these is Golden Rice.
According to Fowler, Scott and Slater; (2003 pp. 247-248), “rice is one of the
most important crops in the world” and in those areas where it is a staple,
“vitamin A deficiency is a major nutritional problem.” Golden rice, which produces vitamin A, was
developed in an answer to this problem.
Naturally occurring rice does not produce this vitamin, but with golden
rice, many will no longer face this deficiency.
Other modification plans include drought resistance, increased protein content, tolerance to frost, and even cotton that produces blue pigment, made especially for the blue jean industry (Nottingham, 2003 pp. 69-79).
Benefits
of Genetic Modification
There are many possible benefits to society, industry, and our economy that GM may provide. As discussed above, GM crops allow higher nutritional values to be incorporated into our foods. Tomatoes are now being modified to be more nutritious, much like the Golden Rice (Fuller, 2004). This increase in nutrition can be especially important in third world countries, where access to a varied diet may be difficult. These advances would help especially in the development of children, and therefore attracts much support.
Another modification affects ripening. In crops such as tomatoes and coffee, the quality of the fruit is dependent on the ripeness stage at which they are picked. Coffee, for example, only ripens a few beans each day, which must be picked within a very specific window of time. With the advent of GM, coffee bushes have been engineered to ripen all their beans within a much smaller window. This allows a farmer to pick all the beans at one time, thereby saving much in the way of labor and increasing efficiency greatly (Rader, 2003).
As discussed above, Bt and Ht crop varieties produce clear benefits for farmers. In each case, a theoretical lessening of sprays is required, which helps to lessen costs to the farmer, and increases efficiency. According to Fuller (2004), “U.S. farmers used 450,000 kg less pesticides on Bt-cotton than they would have used on conventional varieties in 1998.” Tolerance to herbicide allows the crop plant to grow with much less competition, and plants that produce their own pesticide will naturally result in a much healthier plant, as it has not been preyed upon by caterpillars.
In particular, Bt crops have been hailed for their positive attributes. Bt naturally breaks down in the environment, and has been approved by both the EPA and the USDA. It has not been shown to have any ill effects on mammals or other animals other than the target pest. Indeed, this is one of the very attributes that makes Bt so attractive. The very nature of the crystal form is almost exclusively harmful to caterpillars, which are the major pests of a great many crops.
Concerns of Genetic Modification
Despite the benefits that GM crops confer on us, a great many concerns exist that must be considered regarding this issue. While few would doubt the benefit of such a product as Golden Rice, when looking into the idea of increased nutrition a bit further, some problems arise. One example of this is allergies. In an effort to increase the protein content of the soy fed to meat-producing animals, the DuPont Company engineered an amino acid from the brazil nut into their soybeans. However many people have allergies to brazil nuts, and studies have shown that this particular amino acid could cause these allergies to ignite from the soy products (Smith, 2003, pp. 161-162). This could be a source of concern for a great number of individuals suffering from allergies of some kind or another. It can be difficult enough simply trying to exclude peanuts, for example, from one’s diet. With the initiation of GM crops, and widespread gene transfer, it may turn out that a gene shows up in a completely unrelated food, a scary proposition indeed. “More worrisome is that current GM foods get their genes from bacteria, viruses, and other organisms. No one knows if humans are allergic to their proteins- they were never before part of the human food supply” (Smith, 2003, p. 163). While it is true that bacteria is ubiquitous, ingesting a few bacteria on an apple is quite different than eating an entire ear of corn with bacterial proteins in every bite. We’ve known about the foods we’ve been eating for a long time now, but that may change as foods begin to include a range of genes previously not their own.
One major concern with Bt crops is that of insect resistance. Natural selection and evolution have for centuries bred organisms that are adaptable and have good survival skills. Even with new checks such as Bt crops, eventually insects will naturally develop resistances. Once this happens, all the work put into GM will have gone to waste, and may cause widespread difficulties with lowered crop yields, possibly creating shortages of food for feed animals and humans alike. One answer to this problem is the idea of a refuge. The EPA now requires that any farmer planting Bt corn must plant at least twenty percent of their fields with normal corn. The logic behind this idea is that very few insects will mutate and survive with the Bt resistant gene. In the refuge, however, a great many of the pests will survive. When the two groups intermingle, the larger pool of intolerant genes will mask those of the resistant (Chein, n.d.).
While this idea is good in theory, and may even be helpful in practice, there exist problems within it as well. The major concerns are that the frequency of resistant alleles are much greater than expected, thereby not allowing the ‘masking’ that is hoped for. The genetics of insect resistance are not completely understood, and there is evidence showing that the resistance gene may be co-dominant rather than recessive. This would lead to problems, as the resistance would not in fact be covered up with the refuge insects, but instead be sustained. Finally, a logistical problem exists in that resistant insects may emerge several days after the refuge insects, thereby preventing mating, and maintaining a pure strain of resistant insects (Fuller, 2004). If these problems begin to present themselves, then we will shortly have widespread trouble with our widespread Bt crops. Evolution is a constant battle of predator and prey, and to think that we have suddenly developed a catch-all-end-all solution against the pests is simply ignorant. A responsive mutation will certainly occur, and when it does, it will be a problem we must address.
One
of the biggest problems with GM crops is encompassed in a single phrase:
ecological risks. Ecosystems are fragile
things, and with the spread of civilization we have introduced new organisms
into environments that did not hold them previously. One example of this is the
kudzu vine. This is a plant imported
from China and Japan brought to the U.S. as an ornamental shade plant. It was later used in erosion control, but has
since gone wild, and has literally covered seven million acres in the southern
This vine has no predators, and thereby no checks, in the North American ecosystem, allowing it to run rampant. Yet what is proposed with GM crops is roughly the same. Add new features and traits to crops, and then grow them in uncontrolled conditions (outside the laboratory); namely fields. Who can say what ecosystemic interactions might take place? If we cannot predict how a non-modified plant will act, how can we predict how a GM plant will act? The answer is simply that we can’t.
One example of GM plants affecting the ecosystem in is the Monarch butterfly scare. One study showed that Bt corn pollen significantly harmed butterfly larvae when dusted on their normal feeding plant, milkweed. Since monarchs and pest moths are in the same order of insects, naturally the pesticide will affect monarchs as well, though they do not represent the target species. While this pesticide was used previously, it was sprayed only a few times over several years. With GM, however, it is present constantly, and in much higher volumes, providing the basis of the scare. Thankfully, most butterflies do not feed in areas near cornfields, and new Bt strains have been developed that are less harmful to Monarchs (Fuller, 2004). This is a good example of an unexpected result of GM crops, and points our attention to this important issue. How ecologically responsible is it to release these ‘untested’ natural variants on the world, considering our severe lack of understanding of the consequences?
One worrisome effect of GMO’s is the idea of the super weed. Our attempts to modify organisms are generally to give them positive traits not found naturally. But what happens if these traits suddenly pop up in species we don’t want them in? Many of our modern crop species have close cousins that are considered weeds. If the tolerance gene is cross pollinated to a weed, suddenly our Ht crops are useless, and we have a weed that exhibits all the characteristics we wanted to see only in the crop. What good can come from a weed that is more productive, more resistant to pests and herbicides and is generally more resilient? Despite the fact that this is clearly not a goal of ours, and despite the fact that we see it happening (Schmeiser, 2005), we continue in this pursuit.
Compounding this issue is the imprecision with which genetic modification is accomplished. With the gene gun vector, for instance, scientists cannot control where the gold particles end up, and cannot predict with any certainty where the DNA has been inserted. Only a simple preliminary indicator tests gives any clues to what DNA has been accepted. Bowring (2003, p. 42) states that “when an altered DNA molecule is introduced into the genome of a living organism, the full range of its effects on the functioning of that organism cannot be controlled or predicted.” Such concerns as plieotropy (a single protein may serve several biological functions), silencing of genes, or other unexpected interactions within the organism are all frightening. Hopefully laboratory experiments catch most of the dramatic changes in GM plants, but who knows what has already been released with unknown mutations that very well may affect our ecosystem?
As has been explored, the area of GM plants and crops is not a simple issue. It calls up a multitude of arguments, and is clearly not black or white, but some elusive shade of grey. Many of the possibilities of GM are extremely enticing, and seem to offer great potential to many of the agricultural problems we have today. It appears that on a conceptual level, the marvels of GM are quite impressive indeed. What seems to be the case, however, is that when actually implemented, there is a staggering amount of possibilities that could end up occurring, many of them negative. When taking the ideas out of the laboratory, many other unexpected results may surface. Golden Rice may be a great idea, but what allergies may be hiding within the grains? Bt corn may lessen pesticides, but what effect does it have on the food chain and ecosystem it supports?
Percy
Schmeiser is an organic farmer from
It is precisely these questions that are the greatest concern with GM crops. The unexpected interactions within our environment are not a price we should be willing to pay. We have enough on our plate already, and to add more fuel to the fire by releasing GM plants in our world is simply irresponsible. Although genetically modified crops give a wide variety of benefits, the concerns associated with them, and particularly the unknown risks, are not worth the price we would have to pay.
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