Peggy G. Lemaux
February 2, 2001
U.S. farmers have rapidly adopted the new genetically modified (GM) crops since their commercial introduction around 1995. Three major crops in the U.S. have dominated the market, corn, cotton and soybeans; a potato variety has also been planted but on limited acreage. Cotton is the only GM crop introduced into commercial production in CA although GM squash and tomato have been grown here. The traits that have been introduced into the "big three", pest resistance and herbicide tolerance, were for the benefit of the historical agrochemical "consumer", the farmer.
From the period 1995 to 1999, acreage devoted to GM crops in the U.S. increased dramatically. It is perhaps this unprecedented adoption of particular varieties that has made many nervous. In the 2000 growing season, acreage for the GM crops did not increase as it had between 1995 and 1999; predictions for 2001 are also 5-10% lower, most notably in GM corn. This drop has been due to opposition to these crops and to some complicating situations, like StarLink, which has led to fewer markets for the crops. Despite these factors, the continuing use of these GM crops by farmers indicates that they deliver economic benefits to the growers who adopt them.
Despite the rapid adoption by farmers, the variety of commercially available products from the technology is small. Behind these products is a pipeline of improved crops coming out of basic research in academic and private-sector labs that will lead to the next generation of crop plants.
In addition to the direct modification of plant species using genetic engineering or biotechnology, it is important to recognize that the fundamental tools of the technology have provided important advances to farmers worldwide. For example, manipulation of plant tissue in the laboratory has been used to free planting material from diseases. A specific example involves banana, a major food staple and a source of income for over 20 million people in eastern Africa. The availability of clean planting material led to a 50% yield increase for African farmers.
Another indirect uses of the technology provides breeders with road maps of crop plants that tell the breeder which "roads and cities" end up in the plant and whether those "roads and cities" impart the desired characteristics. Use of these tools makes the development of new varieties with all requisite traits easier and faster. Molecular tools are available to monitor for certain diseases, pesticides and other organic and inorganic chemical contamination. These tests can be used to identify plant diseases earlier, allowing the farmer to react faster and reduce chemical usage.
Historically, plant breeders have tried to improve crop plants by selecting for traits that will benefit the farmer, the food processor, or the consumer. These include plants that require less input, are more pest- or stress-tolerant, or produce a higher quality and quantity of protein or starch. They often use, as sources of these desirable traits, wild but related species that, in addition to the desirable traits, have large numbers of undesirable characteristics, which are hard to eliminate by classical breeding.
With genetic engineering more precise changes can be made that eliminate some of the unexpected outcomes of classical breeding. Why, because we are moving specific genes, which have been thoroughly characterized. Does this mean that crops developed with these methods are without unexpected consequences? Probably not, but the number of instances where this occurs will be no higher, or perhaps lower, than it is with classical breeding techniques.
The first category of changes for GM crops is in what is termed "input traits", ones of value to the farmer. These include pest resistance strategies, many of which depend on naturally occurring defense mechanisms. After all plants cannot get up and run away when attacked by a pest and therefore many, especially wild relatives have innate capacities to withstand attack. One example of such a strategy is the use of a natural resistance gene to protect tomato from aphids and the root pest, nematode. Another is the protection of papayas from a viral disease, papaya ringspot, which nearly decimated fields in Hawaii. Other strategies are focused on insect resistance, such as one developed here at UCSD that protects beans from attack by bruchid beetles. Another category of input trait would include improvements in the performance of the plant in the field, like stress-tolerance (e.g., salt, drought and cold) or lower fertilizer inputs. Modifications have and are being made in post-harvest characteristics that make it easier to harvest cherry tomatoes or lead to lower spoilage in harvested fruits, like melons and raspberries.
A second broad category includes what are termed "output traits". These include foods from which something has been removed, which has an adverse effect on its consumer, or something that is added that makes the food better for the consumer. In the first category are foods with lower allergenicity, like hypoallergenic rice or wheat, or coffee from which caffeine has been removed. The second category, foods with improved nutritional quality, includes Golden Rice, a rice with high levels of beta-carotene, a precursor to Vitamin A. This rice, which contains three different genes, two from daffodil and one from a bacterium, is a potential supplemental source of vitamin A. A potato has also been created that has higher protein quality and quantity and a white clover with improved forage quality. These foods are also called "value-added"; another example of a value-added trait is making natural artificial sweeteners, known as fructans, in sugar beets.
A step further in nutritional enhancement is using plants to deliver medicines, sometimes also known as nutriceuticals. Examples of these include edible vaccines. In developing countries where introduction and/or delivery of disease-preventing medicines is sometimes difficult, these new edible vaccines might be effective vehicles for disease prevention, such as cholera and rabies. This approach might also be useful in preventing certain types of cancer, like non-Hodgkin's lymphoma. In the U.S. another potential use might be in protecting animals against disease. Plants can also be used as miniature "pharms" to make drugs, like "plantibodies", human therapeutic antibodies used to treat certain types of diseases, like cancer.
Plants are a great renewable resource. They can be engineered to produce products now made from nonrenewable resources, such as industrial oils, detergents, gasoline substitutes, and biodegradable plastics. Since plants can be easily grown and harvested, year after year, they provide potentially renewable sources of these compounds.
Another target for plant biotechnology is environmental cleanup. Mechanical methods of removing pollutants from the soil are not always very efficient or even feasible. But plant roots are capable of reaching deep into the earth or aquatic ponds to remove organic or inorganic pollutants, e.g., mercury, PHCs, and selenium. The plant roots act as chemical sponges taking up and retaining the pollutant. A challenge of this approach is to "teach" the plant to move the contaminant from the roots to the above ground mass so that it can be harvested and the metal or contaminant removed.
Lets return to the existing commercial crops and see what real and potential benefits there are for the farmer and the environment.
B.t. corn is resistant to the European corn borer (ECB), a pest which burrows into the stem of the corn interfering with nutrient and water transport. As soon as the larvae enter the stem, they cannot be treated effectively with chemicals, so the farmer has only a short time for effective chemical pest control. Because it is difficult to anticipate the degree of insect pressure in a given year, many farmers must accept yield losses in years of heavy infestation. This can lead to losses of up to 7% of the total U.S. harvest, resulting in >$1 billion in damage and control costs per year.
The advantage of a plant producing its own insecticide, like B.t., is that farmers do not have to spray it on the plant and the delivery of the insecticide to the target insect is efficient. Every bite the insect takes contains the insect-control chemical, assuring that they come in contact with the pesticide. This has led, in high infestation years, to reduced damage by insects and higher yields. For example, in 1997, a high infestation year, the yield premium of B.t. corn was ~ 12 bushels/acre. A secondary benefit is that B.t. ears were less infected with fungus and the levels of fungal toxins, like mycotoxin, were lower.
But, a word of caution. B.t. seeds are more expensive than conventional ones, so in years when insect pressure is low, yield losses to insect damage are low and the cost of seed is not recovered. Estimates are that in 3 out of 13 years insect pressure will not be sufficient for farmers to make profits with GM seeds; 1998 and 1999 are examples of such years.
What about B.t. cotton? According to data collected from 1996 and 1997, farmers received the biggest share of financial gain from planting B.t. cotton. The total increase in world supplies of cotton in 1997 was worth $190.1 million; U.S. farmers share of this total surplus was 42%. The company that developed the variety, Monsanto, received 35%, and Delta and Pine Land, which provided seeds to farmers, received 9%. The US consumer received the smallest part of this surplus, 7%. The distribution of surplus in 1996 was quite similar, except farmers received a larger share, 59% and the company a smaller share, 21%. Besides the economic benefit, there is also an environmental benefit to Bt cotton. Due to its adoption, there was a reduction of 2.2 million pounds of insecticides used on cotton in 1997, when compared to 1992 pesticide-use figures.
One of the difficult challenges of farming is the control of weeds. In the middle of the last century chemical control with herbicides became feasible and in 1997 approximately 461,000,000 pounds of herbicides were used in the U.S. But the identification of effective herbicides is difficult because the chemical has to distinguish between a weed and a crop plant, not easy given the similarities in the two plants. Aside from chemicals, other methods are used to control weeds. One approach utilized genetics, through breeding or mutation, to develop crops tolerant to certain herbicides, so the crops could grow, while weeds could not.
With the new tools of genetic engineering it became obvious that one could fairly easily engineer a plant with an herbicide tolerance gene, capable of inactivating or averting the effects of the chemical. By doing this, the HTC (herbicide-tolerant crop) would be able to survive herbicide application while weeds would not. There are advantages for farmers of HTCs and also potentially for the environment.
Issues of insect resistance to B.t. will occur, although it is not known when. Measures have been implemented to slow the process of resistance development and it is in the best interests of farmers and the company to do this. However, it depends on the "refuge" system, in which a farmer devotes a % of his acreage (usually 10%) to non-B.t. plants, thereby taking a yield hit on this land, a potential problem in developing countries.
Problems can arise with herbicide-resistant weeds that result from overuse of particular herbicides, and weed shift, a problem where naturally resistant weeds invade an area where a particular herbicide is repeatedly used. These problems occur with conventionally bred crops as well, but with HTCs it is a matter of scale and the fact that only one HTC strategy is available in a variety, encouraging overuse of an herbicide.
Problems might also occur from out-crossing of HTCs with wild relatives that then become weeds. If these HTCs are to be useful for many years, weed management practices must be implemented to prevent such incidents. An example of the potential for this problem is a triple-resistant canola that resulted from outcrossing, causing it to become a volunteer weed in subsequent years. Is this an ecological disaster? No, but even though it is controllable with alternative herbicides, it lessens their usefulness to aid weed control.
Whether pollen drift presents significant agricultural or human safety risks cannot be generalized; it must be examined on a case-by-case basis, depending on the crop, the nature of the introduced genes and the location of the release. A major factor is whether the crop is self-pollinating, like wheat and soybeans, or is open pollinated, like corn and canola, since this greatly affects whether genes will flow from one plant to another. Second, pollination success depends on how long pollen is viable and the distance between plants; some pollen can travel farther while it is still viable. Pollen drift from GM crops to non-GM crops is likely to happen, but mostly with open-pollinated crops. It appears this has already happened with canola and possibly with StarLink corn.
There are different reasons for farmers to worry about pollen drift. An organic farmer will worry if he/she lives near a farmer growing GM crops; it is also likely a problem for the farmer growing the GM crop. This is an issue because the new organic rules guarantee that organic foods do not contain GM ingredients. This is not unlike the problems that have occurred in the past with herbicide- and pesticide-drift to organic farms from aerial spraying of conventional farms.
Another problem for farmers might occur when they try to export their products to Europe. At the present time, certain European countries do not import all new U.S. GM crops. Contamination of commodities with these GM varieties can prevent farmers from exporting to Europe (and Japan) although there are other markets, domestic and other international (e.g., Canada, some Asian markets, Mexico), that accept these varieties.
Although outcrossing can occur, a bigger concern for large-acreage crops relative to contamination of GM and non-GM varieties has to do with an inability to segregate varieties adequately during harvesting, shipping and processing. A case-in-point is the incredibly costly contamination that occurred with StarLink corn.
Despite the potential for biotechnology to provide options to the farmer in the near- and long-term and to consumers in the long-term, a portion of the public is nervous about the products of biotechnology and who is developing them. Why are they nervous? It is in part an issue of risk and safety. Risk can be quantified and scientists have participated in that process. But, safety is defined on an individual basis as acceptable risk. Let's look at an example. When the airplane first arrived on the scene, very few individuals took advantage of this form of transportation in large part because they did not feel that it was "safe". Now people use this form of transportation frequently. That is because, even though passengers know that a certain risk is involved, the benefits outweigh the risks. Faced with the need of getting from San Diego to NYC in one day, the customer, except for John Madden, usually finds the alternative to flying untenable! How does this apply to the situation with the new GM foods? To date with the new GM foods, the consumer sees little benefit.
Some new GM crops are in commercial production. Is the Roundup Ready Soybean the end of the road for these technologies? No, they represent the rather crude, first efforts, similar to the original computer that took up blocks in New York City. The average consumer could not see personal advantage to such a machine, but now we carry the same computing power in machines the size of a notebook. Consumers have not realized any direct benefits of the early GM products. They were aimed at farmers and their continued use attests to their benefits. But, the broader community is passing judgement on their utility and that jury is still out. If these new crop species yield environmental benefits that can be demonstrated and if they are shown to be safe for consumers, then it is likely they will ultimately find favor with consumers. If not, then the marketplace will speak and the impact of the technology will be minimal.