The Convention on Biological Diversity provides a broad definition for biotechnology, i.e., "any technological application that uses biological systems, living organisms, or derivatives thereof, to make or modify products or processes for specific use." This definition covers traditional tools and techniques commonly used in food and agriculture such as fermentation technology to produce the Chinese hoisin sauce (a soya-based sauce), the Korean kim chee (vegetable pickle), the Japanese sake, the Vietnamese nuoc mam (fish sauce), to mention some examples in Asian culture, as well as the wines and cheeses of Western cultures such as the French Camembert and the Italian Parmigiano. Non-controversial techniques such as tissue culture and traditional plant breeding, including the use of chemicals and radiation to induce mutagenesis for crop improvement, are also covered by this definition.
The Cartagena protocol on biosafety, however, defines "modern biotechnology" in a more narrow sense. This definition covers applications of: (a) in vitro nucleic acid techniques, including recombinant deoxyribo-nucleic acid (DNA) and direct injection of nucleic acid into cells or organelles or (b) fusion of cells beyond the taxonomic family (that overcome natural physiological reproductive or recombination barriers and that are not techniques used in traditional breeding and selection). Modern biotechnology, hence, encompasses the noncontroversial use of: (1) recombinant vaccine; (2) DNA markers for gene mapping, disease diagnostics, genetic resource characterization, DNA marker-assisted section in plant breeding, and DNA fingerprinting; and (3) the currently controversial genetic engineering to produce genetically modified organisms (GMOs), including the so-called transgenic crops, also called GM crops or GE crops.
Operationally, biotechnology consists of two components: (i) tissue and cell culture and (ii) DNA technologies, including recombinant DNA and genetic engineering. Both components currently are essential for the production of GM plants, crops, and animals.
Plant tissue and cell culture are relatively low-cost technologies, simple to learn, easy to apply, and widely practiced in many developing countries. Plant tissue culture aids crop improvement via micropropagation of elite stocks through in vitro culture of meristem, providing virus-free planting stock; generating somaclonal variants with desirable traits; overcoming reproductive barriers; and bringing desirable traits from wild relatives to crops through embryo rescue or in vitro ovary culture and pollination. Gene transfers from distantly related species can also be facilitated through cell culture and plant protoplast fusions whereas anther culture with doubling of chromosomes to obtain homozygous lines can help to speed up time in a plant breeding program. Tissue culture is particularly useful not only for in vitro conservation of plant germplasm but also for the exchange of disease-free germplasm among countries.
Animal cell and tissue culture are widely practiced in developed and technologically advanced developing countries, in particular for medical research. For livestock improvement, simple artificial insemination is widely practiced in developing countries whereas developed countries apply a wide ranging of advanced technologies, including semen sexing, embryo sexing, embryo transfer, in vitro fertilization, embryo cloning, and somatic cloning. The latter was used to clone Dolly, the sheep.
The second component of biotechnology includes DNA-based technologies and genetic engineering which make use of DNA sequences as molecular markers, the knowledge of the genes and the genetic code (DNA) for improvement of crops, trees, livestock and fish. The uses of DNA-based markers, which are not controversial, assist in the characterization of genetic resources for conservation and crop improvement. DNA markers are particularly useful for gene map construction for gene isolation and for marker-assisted selection (MAS) in conventional plant breeding programs. MAS is widely practiced in the private sector (Ragot, 2003) and can help to accelerate corn, soybean, and wheat-breeding programs (Mazur, Krebbers, and Tingley, 1999; Orf, Diers, and Boerma, 2004; and Ward, 2003). MAS are particularly useful in breeding for disease and pest resistance because they eliminate the need to introduce pests and pathogens for screening purposes. DNA markers are also important for diagnostics of diseases and pests, including monitoring pest populations for their management.
Although currently controversial, the most important feature of genetic engineering, also called genetic or DNA transformation, is the ability to move genes even across kingdoms, helping to enlarge the gene pools for all organisms. Genetic engineering allows useful genes from any living organism to be transferred to crops or animals for improving their productivity. Genetically altered bacteria or trees can be used in soil remediation. Furthermore, biosynthetic pathways can also be manipulated to produce added nutritional compounds in crops for food and feed, high value pharmaceuticals and other polymers, using plant and animal as bioreactors. The few examples of technologies present today only vaguely portent the vast implications for potential importance of biotechnology on agriculture in the next two decades.
3. CURRENT BIOTECHNOLOGICAL RESEARCH RELEVANT TO AGRICULTURAL DEVELOPMENT: THEIR POTENTIAL AND REALIZED IMPACT
Although the current commercial GM crops target simple traits and single genes, technological advances now permit the transfer of as many as 12 genes into a plant genome (Chen et al., 1998). Importantly, the recent development of binary bacterial artificial chromosome (BIBAC) (Hamilton et al., 1996) and transformation-competent artificial chromosome (TAC) (Qu et al., 2003) vector systems which are capable of transferring large foreign DNA fragments up to 150 kilobase into a plant nuclear genome, are useful breakthroughs for map-based cloning of agronomical important genes. This should accelerate gene identification and genetic engineering of plants (Hamilton et al., 1996). Such development may facilitate the alteration of more complex traits such as yield and tolerance to drought, salinity, heat, chill and freezing, as well as tolerance to problem soils such as salinity and aluminum toxicity.
One of the main criticisms of the GR has been that it bypassed poor farmers living in marginal environments and those who cannot afford the cost of inputs such as pesticides, fertilizers, and infrastructure cost for irrigation. The gene revolution is actually providing some measures to address these concerns, with GM crops that produce their own pesticides (such as the current crops of GM crops with various Bt genes transferred from different strains of the soil bacterium, Bacillus thuringiensis) and are efficient in nutrient uptakes. Concerning phosphorus, Mexican researchers at Centro de Investigaciones y Estudios Avanzados (CINVESTA) have demonstrated that GM tobacco and tropical corn are highly productive under low phosphorus soil conditions. However, these lines have not been tested under field conditions since 1999 due to the pressure from anti-GM groups (Herrera-Estrella, 2002). In addition, a research group at Purdue University has cloned a phosphate transporter gene from Arabidopsis. These genes were also found in other crops such as tomato, potato, and alfalfa. This will allow the development of GM plants with more efficient uptake of phosphate (Muchhal and Raghothama, 1999; Mukatira et al., 2001). Scientists are conducting research on biological nitrogen fixation with the objective of making nonleguminous crops, such as rice, fix their own nitrogen, or expanding the host range of nitrogen-fixing bacteria so that more crops can have such symbiotic relationships. This would also help to protect the environment by saving fossil fuel needed to produce nitrogen fertilizer.
3.2 Utilization and rehabilitation of marginal and degraded lands
In many regions of the developing countries, considerable areas of land exist that are unusable for agriculture due to soil and related constraints; other areas are utilized but produce suboptimal yields. Evidence indicates that there is great potential for increasing productivity in marginal areas. The pioneering work by Mexican, followed by American, researchers in elucidating the molecular mechanism of aluminum tolerance and in developing GM plants resistant to this toxic ion would have great impact on developing countries (de la Fuente et al., 1997; Mesfin et al., 2001), particularly in opening up vast areas in the Brazilian Cerrados and West African moist savannah to more intensive cultivation. Since acid soils cover 43% of tropical areas, aluminum-tolerant crops would help to extend crop production in these otherwise low-productivity lands without incurring the costs of soil amelioration.
On the other hand, 30% of arable land is alkaline, making iron unavailable for optimum crop production. Japanese workers recently demonstrated that a GM rice, engineered with barley genes, showed an enhanced tolerance to low iron availability and yielded four times more than nontransformed plants in alkaline soil (Takahashi et al., 2001). Encouraging results are also being made in the area of salinity tolerance. In the presence of 200 mM NaCl, GM tomato and canola plants reached maturity with very good fruit set and oil quality, respectively (Apse et al., 1999; Zhang and Blumwald, 2001; Zhang et al., 2001). In addition, climatic variability such as sudden drought or frost may have severe consequences for resource-poor farmers living in marginal environments.
3.3 Stabilizing yield potentials under dehydration stress of drought, salinity, freezing, and chilling
Biotechnology applications of research on environmental stress tolerance may ensure poor farmers of a stable harvest. Research into the physiological and biochemical basis for abiotic tolerance has been greatly aided by advances in molecular biology. American researchers working on freezing resistance (Jaglo-Ottosen et al., 1998) and Japanese researchers working on drought tolerance (Kobayashi et al., 1999) have isolated the same transcription factor from Arabidopsis thaliana, commonly known as thale cress, a weedy relative of canola (rapeseed), that when overexpressed in GM plants resulted in significant tolerance to drought, salt, and freezing stresses. The transcription factor, named CBF1 by the Americans, and DREB1A by the Japanese, was responsible for controlling the expression of other regulatory genes when plants undergoing dehydration stress. The WeatherGard™ technology is based on the CBF family of transcription factors. Accordingly, transgenic canola with the Arabidopsis transcription factor gene, CBF1, also shows drought tolerance as compared with its nontransgenic control. The WeatherGard™ technology also confers freezing, salinity, and drought tolerance in tomatoes. At the Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), the WeatherGard™ transgenic wheat seedlings with a drought-inducible promoter also show better recovery after 15 days without water (Goure, 2002), whereas at the International Rice Research Institute (IRRI), transgenic rice with DREB1A gene driven by the stress inducible promoter, rd 29A, showed very high drought tolerance at vegetative phase after three weeks without water and at reproductive phase after one week without water (Datta, 2004). Recently, German researchers investigating the molecular mechanism of drought resistance in the resurrection plant Craterostigma plantagineum (a native of South Africa) uncovered novel ABA- and dehydration-inducible aldehyde dehydrogenase genes which also have their homologues in Arabidopsis. Transgenic Arabidopsis overexpressing the genes were found to survive longer periods of drought (16 days) as compared with 12 days for nontransgenic (Kirch et al., 2001). Researchers at Cornell University recently reported that they had developed transgenic rice overexpressing trehalose that was more drought-resistant than the nontransgenic control (Garg et al., 2002).
The above examples indicate that biotechnology tools may help to bridge the gap between potential and actual average yields in developing as well as developed countries. Furthermore, these tools may help to move the yield potential to a higher level. The demonstrated yield increases—of 10% to 35% for GM rice overexpressing corn's photo-synthetic enzymes (Ku et al., 2000) and fourfold for GM rice with a barley gene for its tolerance to low soil iron in alkaline soils (Takahashi et al., 2001)—allow for such optimism.
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