Biotechnology And Agriculture

While looking at agriculture with regards to biotechnology, three main parts are of great interest: these are plant, food and animal biotechnology.

Plant biotechnology

Seeds, tissues or plant cells can be manipulated genetically, transformed and then regenerated into a whole plant. New plants can also be created by integrating into a plant's DNA a new DNA that will become a permanent part of the plant: the final product is called a "transgenic" plant. But in all cases, natural characteristics are being altered or new characteristics are being added to make plants more desirable. Many plants have already been genetically manipulated: some examples are tomatoes, potatoes, soybeans, carrots, canola, corn, rye, beets, alfalfa, rice, sunflowers, pears, apples, and cabbage. Sophisticated plant breeding methods are also generating many new varieties of agronomically important plants.

Plant biotechnology is certainly a growing sector; according to the Biotechnology Industry Organization, in 1996, over six million acres of land worldwide were planted with genetically engineered plants for commercial use. More than 15 genetically engineered agricultural products already are on the market and many more can be expected in the next three to six years. (Barnum, 1998).

Application of plant genetic engineering

1. Crop improvement

   Research on crop improvement has focused until now on agronomic traits for controlling insects, viruses, bacterial and fungal plant diseases and weeds. Other modifications will include developing new, more nutritious food products, manipulating the petal color of flowers, and synthesizing biodegradable, organic plastics. A very promising area of research is the production of specialty oils for detergents, cosmetics, and lubricants, and the modification of the lipid composition of seed crops to reduce levels of saturated fats (refer to non food uses of agricultural products). Also, the fact that crops may one day be cultivated in areas that are currently less suitable or marginal (due to the loss of prime farmland from urbanization) is accelerating the development of crop varieties that are capable of growing in such conditions.

2. Herbicide resistance

   Weeds often significantly lower crop yields by competing with crop plants for nutrients, water, light and carbon dioxide. Unfortunately, methods that promote crop growth, such as fertilizers, also stimulate weed growth. Weeds make good competitors for several reasons:

   1. They have very effective reproduction modes and highly evolved seed dispersal mechanisms. Each plant produces a multitude of seeds, which can remain dormant for long periods of time and do not always germinate at the same time.

   2. Some weeds produce seeds throughout the growing season and so re-seed themselves several times during the season.

   3. Weeds are fast-growing and can tolerate drought and low nitrogen levels much more so than most of the crops they compete against.

   4. Weeds are often self-fertilizing, wind-pollinated, or pollinated by unspecialized insects.

   5. Weeds often outgrow other plants and form large root systems that are difficult to uproot. (Barnum, 1998)

   (Refer to pesticides section) Herbicides are widely used to decrease the impact of weeds on crops. But even if farmers routinely apply more than 100 chemical herbicides, weeds still reduce crop yields by an average of approximately 12%. Also, since many herbicides do not discriminate between crop and weed, they must sometimes be applied at specific periods, such as before the crop germinates and emerges. This presents management problems and restrictions on crop rotations as chemicals can persist in fields and limit yields and even kill following crop plants.

   Some plant varieties such as corn, potatoes, soybeans, tomatoes, and cotton have been genetically engineered to resist the toxic effects of certain chemical herbicides, allowing the herbicides to be used where they would otherwise injure or kill the crop plants. There are both advantages and disadvantages to the application of this type of biotechnology. By engineering a very specific plant-herbicide relationship, the crop can be more efficiently managed and produce greater yields on average; depending on the weather of any particular year, herbicide-tolerant crop varieties may actually result in a lower use of pesticides in general. On the other hand, these herbicide-tolerant plants are developed by or in conjunction with companies that also develop herbicides. In this manner, the chemical approach to weed control continues instead of developing alternative products and practices that are less of a risk to the environment; biotechnology, in this case, actually perpetuates the dependence on chemical applications in agriculture rather than alleviating the situation. This dependence may generate more herbicide-resistant weeds (see pesticide resistance), which in turn negates the positive effects of such new technology. There is also the risk of accidental cross-breeding between herbicide-resistant crops with neighboring related wild plants, thereby creating a herbicide-resistant weed.

3. Insect Resistance

   Huge losses result to crops in the field as well as the stored cereal grains, peas, and beans attacked by insect pests. Recently, garden pea seeds have been engineered to resist attack by two species of weevils that damage crops in storage. How? A protein blocks the action of a specific enzyme in the pest that digests the starch in seeds. In studies, most of the weevils that fed on these genetically engineered peas either died or suffered inhibited development. Interestingly, the inhibitor protein is expressed only in the seeds of peas. Eventually, other legumes such as pinto, kidney beans, black-eyed peas (cowpeas) and chickpeas will be protected from insect attack.

   For several years, farmers have been able to sow "Bt corn" as a non-chemical alternative to dealing with the corn-borer insect which damages the roots of the plants and therefore inhibits the growth of corn stalks and affects yields. The biotechnological process inserts the bacillus thurengensis (hence the name Bt) a bacteria which infects the corn-borer and then kills it when the insect tries to eat the corn plant. Hailed as a major breakthrough in non-chemical crop protection, the use of Bt is limited by the fact that the corn borer can quickly become resistant if Bt corn is repeatedly planted in the same fields. Unless farmers rotate their crops between different fields - corn seed companies are even advising farmers to alternate corn crops between Bt and ordinary varieties - the corn-borer will make Bt corn ineffective through resistance.

4. Viral Resistance

   Many crops are lost to viral diseases, resulting in losses of millions of dollars each year. Of course, chemicals are widely used to control the insect vectors that spread viral diseases, but genetic engineering may provide a more desirable alternative to chemicals in the form of "plant vaccines". Genes involved in resistance to diseases caused by viruses, bacteria and fungi have been isolated; virus-resistant crops such as melons, tomatoes, squash, cucumbers, and potatoes can then be generated by having a gene transferred that encodes a viral coat protein. The plant then expresses a small amount of viral protein and, although the exact mechanism of protection is unknown at this time, the virus cannot replicate and spread in an "immunized" plant.

5. Plants as bioreactors

   One day whole plants may be used as living bioreactors (just as microbes are already being used) by inserting a foreign gene to produce proteins of therapeutic and industrial value. An inexpensive, readily available complex metabolite could be used as a nutrient source, and cells could then convert this compound into a valuable product, which accumulates until the cells are harvested. Trials are already underway using alfalfa plants to produce compounds out of which specialized and high-end plastics could be produced. Whole plants would then be harvested and the product extracted, allowing producers to avoid complex in vitro biosynthetic reactions in the laboratory. (Barnum, 1998)

   Soybean plants have already been used recently as bioreactors to produce a variety of monoclonal antibodies with therapeutic value (such as for treatment of colon cancer). What brings scientists to explore this field is that the cost of producing foreign compounds in plants may be much lower than producing them in bacteria and mammalian cells and much more advantageous, mainly because commercial scale-up involves simply planting seeds rather than using costlier fermentors.

Food biotechnology

"The term 'food biotechnology' is used to describe a variety of recent technological innovations for producing and processing food. These technologies share an emphasis on cellular and subcellular manipulation of organisms and commodities that contribute to the production and processing of food." (Thompson, 1997)

The first genetically engineered food

The "Flavr Savr" tomato, developed by Calgene, Inc., a biotechnology company in California, was the first genetically engineered food to gain government approval in any country. It was approved in May 1994 by the Food and Drug Administration (FDA) in the US. The Flavr Savr generated much discussion and raised controversy about food engineering. The FDA ruled that the Calgene tomato was as safe as a conventional tomato and did not require specific labeling in markets to indicate which gene had been added or that it had been genetically modified.

In fact, the Flavr Savr tomato offers many benefits, including a garden-fresh taste all year round. Of course, this feature contrasts with the rather tasteless varieties that must be picked at the onset of ripening to avoid over-ripening and softening by the time they reach market. Although the green, unripe tomatoes are gassed with ethylene to turn them red, time does not allow them to develop any flavor. The Flavr Savr has been genetically altered to soften more slowly so that the fruit can remain on the plant until ripe. Thus, the tomatoes stay fresh without rotting and deliver natural flavor all year. The sale of fresh "normal" tomatoes declines by as much as 30% from October to June when they are not as tasty. The Flavr Savr can help increase sales during those months.

But opponents of genetically engineered foods have expressed concerns that the consequences of introducing "foreign" genes into a food that is then consumed by humans are unknown, that considering the risks of reactions, allergies and other effects, such genetic manipulation should not be allowed to proceed until society has a better understanding of the situation. There are also concerns that while the intended and beneficial effects (a tastier tomato) may result, there might also be unintended changes in the plant from the gene manipulation and that if the plant should cross-breed with other varieties, a detrimental variety may be released into nature with disastrous consequences; the escape of African killer bees being studied in South America, and the subsequent cross-breeding with and demise of native species is often cited as an example of uncontrollable outcomes.

There are also concerns that the FDA approval of the tomato will open the door to many other genetically engineered foods in the near future, which indeed is likely to occur. Over 50 bioengineered foods are expected to be ready for the commercial market by the year 2000. One product that may already have a promising future is a potato variety in which the starch content has been increased by 40%, making a potato chip with better texture. Vegetables and fruits in the future may have a higher sugar content; controlled conversion of sugar to starch in peas and corn, for example, will help these foods remain sweeter after harvest. Future products also include a naturally decaffeinated coffee bean, high protein corn (which is naturally high in starch and low in protein), and new crops that can be grown with fewer toxic herbicides and pesticides and with less irrigation.

Animal biotechnology

Below: goats at Nexia Biotechnologies Farm.
For more about them, see the Profile of Isabelle Tremblay-Summers

Selective animal breeding, a biotechnological practice, has been practiced for nearly 10,000 years to produce desirable traits in livestock; these would include how quickly an animal grows, how much milk, or meat or fat is produced, and the number and health of the offspring. So animal biotechnology is not new, but with traditional selective breeding, producing desirable traits takes time and many generations of animals must be born and bred before an appropriate trait is finally expressed.

Today, however, breeders are under increasing market pressure to produce livestock that grow faster and convert animal feed to lean tissue, with less total fat, that are disease-resistant, that produce a better wool quality in the case of sheep, or lay eggs with an increased frequency in the case of hens. Recombinant DNA technology, that allows the introduction of foreign genes into organisms for the expression of specific new traits, appears to be an efficient way to accelerate the traditional breeding process. Genes can be transferred across species, families, and even kingdoms of animals.

This technology can also be used in other ways. Bovine somatrophin, or BSt, is a growth-hormone which naturally occurs in dairy cows, and which acts as a signal when emitted by the pituitary gland to have the cow release milk from the udder; the more BSt in the cows system, the greater the release of milk. Recombinant DNA technology now makes possible the insertion of the BSt gene into bacteria, which then reproduce and the BSt is extracted from these cells using centrifugal force; the same procedure is used to produce 'synthetic' insulin for human diabetics. With the necessary quantities of BSt now available, cows can be injected with BSt to stimulate greater milk production. Use of the growth hormone anabolic steroid has been approved in the US but not in Canada. In a classic biotechnological dilemma, the farmer benefits from higher production at lower cost, an economic benefit also passed through to consumers. There are questions, however, about the side-effects of using the synthetic version of the growth-hormone: do dairy cows receiving injections suffer high levels of mastitis; what effects on humans are there from the increased levels of the hormone present in the cows' milk; is there a difference between the natural and the synthetic versions of the hormone; do higher levels of the hormone stimulate equally high levels of other hormones which, even if BSt is safe, might have effects on human health; and what about the ethical question of giving cows injections just to produce more milk? There are no ready answers (see section on biotechnology ethics) and highlight the great potential and possible drawbacks of using biotechnology.

Major goals of animal biotechnology

1. Breeding livestock that are more economically produced
   This can be achieved by increasing growth rate and muscle development with growth-hormone genes from various sources, or by producing antibodies and recombinant vaccines to increase disease resistance.

2. Breeding livestock to produce products that are more nutritious
   Leaner meat or lower-fat milk with higher natural calcium content are examples of what biotechnology could provide for the consumer.

3. Development of animal "bioreactors"
   Animals, as it is the case for plants, could be used to produce rare pharmaceuticals and other medical compounds. Genetically engineered livestock could produce important health products within composition of milk or blood, which can be used for treating a variety of human diseases and health needs. Among such products might be human hemoglobin, which could be used during trauma when much blood has been lost, human protein C, which helps prevent blood clotting, or human tissue plasminogen activator which is used to treat patients after a heart attack.