Genetic engineering and modification brings with it great potential to the agricultural industry, which could prove extremely beneficial to society. This essay will focus on the recent and current developments within this industry, highlighting both the advantages and pitfalls in this area of biotechnology.
Genetic manipulation of crop species is nothing new, around 8000 years ago native Americans domesticated the wild plant Teosinte, selectively breeding the species for higher yield and greater growth, transforming this plant with short ears and small kernels into what we would now recognise as corn (Falk et al., 2002). This rudimentary form of biotechnology, designed to give desirable phenotypes created a stable characteristic that could be passed through generations through the preservation of consumer advantageous genes. This was, and to a large part of industry still is, the conventional method for crop production, but lacks any control at the genome level and has a limited scope for the variety of species that can be successfully crossbred (Day 1996).
Over the past two decades these techniques have been challenged by the progress made in genetic manipulation, allowing the "transfer of a single gene from one living organism to another - regardless of species" (Gianessi and Carpenter 1999). This has revolutionised the way scientists have viewed the problems associated with crop production, transforming several species to contain specific traits that could not be achieved via traditional methods.
The Flavr-Savra® tomato was the first such genetically engineered food crop to enter the market in 1994, modified to delay ripening and although heralded as a scientific breakthrough, was ultimately a commercial disaster due to inflated prices over regular tomatoes and poor yields. By early 2001 over 187 genetically modified crops had been approved for planting or foodstuff use in one of 13 major countries or the EU (Marra et al. 2001). These crops are engineered to control pests or diseases, increase nutrient availability or improve crop characteristics, these improvements in are inextricably linked to changes in the environment and economy (Mannion 1995).
"GM" crops are created by a number of methods, --------------------------. It is also growing in recognition and importance with the Ives et al., 2001 stating that the "global area of transgenic crops in 1998 is estimated at 27.8 million hectares, a 2.5-fold increase over 1997." This growth however may be needed in an effort for sustainable, cost effective agriculture with the world population on the rise and projected to increase to 10billion over the next 40years (Ferry et al., 2003).
The applications of genetically modified crops are virtually limitless and could help alleviate world poverty and increase health in developing countries, but must be proven to be safe as both crops foodstuffs and have been associated with much media attention (Hoben 1998) as well as intellectual property (IP) issues (Barton 1996).
The advantages of genetically modified crops over their traditional counterparts are widespread and significant and can provide benefits for both the consumer and the producer. Until recently however, the focus was on "input" traits or those that relate to modification for commercial sectors, giving higher yield or greater tolerance to stress, benefiting the producer (Falk et al., 2002).
A well documented example of this genetic modification of potato, maize and cotton plants to contain the δ- endotoxin from Bacillus thuringiensis (Bt) (Ferry et al, 2003: Falk et al., 2002). The B.thuringiensis had long been known to produce a substance toxic to specific insect larvae, with organic farmers historically spraying crops with the common soil bacterium to reduce European corn borer, potato tuber moth and cotton boll worm numbers (Ives 2001). The distinct advantage of this toxin is that although and effective pest control method it is harmless to humans, increasing yield and in the case of the European corn borer reduces the levels of fumonosin which is a mycotoxin, associated with liver damage in animals (Munkvold et al., 1999). This provides both a health benefit and an economical one, reducing the amount of crop wastage and negating the need for a farmer to purchase insecticide, which cost US field corn growers approx. $380million per year (Gianessi, 1995). In addition to this, various tomato and fruit varieties have been engineered to withstand virus and insect threats (Marra et al., 2001).
Along with pest resistant strains, crops engineered to withstand elevated abiotic and biotic stress have also been made commercially available, and through gene marker techniques it has been realised that the introduction of a small number of genes in an agricultural crop is now financially viable to enable a crop to survive in otherwise adverse conditions (Cushman and Bohnert, 2000). These advances have proved fruitful, such as plants being transformed to contain a bacterial gene coding for manitol-1-phosphatedehydrogenase (mt1D), an osmoprotectant in cholorplasts. These osmoprotectants, help stabilise the proteins and cell membranes against being denatured, leading the crop to have elevated oxidative stress tolerance (Shen et al., 1997). This shows promise, both in increasing productivity and enabling crops to be planted in less favourable environments (Falk et al., 2002) and would be particularly beneficial in the third world.
Plant metabolic and photosynthetic pathways are also under review and consideration, with a view to making these more efficient, increasing crop yield and timescales. An example of this is improving nitrogen assimilation as detailed in Oscarson (2000). Decreasing perishability of foodstuff is also a primary concern for agricultural farmers, such as the attempt with the Flavr-Savra® tomato, this employed a technique enabling the silencing of a gene coding for the polygalacturonase, an enzyme which degraded pectin in the ripe tomatoes, allowing them to remain firm for longer (Redenbaugh et al., 1993).
The methods through which "GM" crops are produced has also led to significant advantages, reproduction through tissue cultures in itself can lead to the generation of virus-free varieties of strawberries, potato and tobacco species among others, through treatment of infected tissue cultures or by the culturing of virus-free cells. Tissue cultivation production is markedly quicker than traditional methods and requires less land, especially for those that would otherwise need to be hand pollinated (Mannion 1995). Cassava (Manihot esculenta Crantz) is an important example of this, this staple crop in developing tropical countries is susceptible to a wide range of pest and diseases with a screening technique employed allowing for the discovery of resistant wild types which then could be planted (Roca 1989).
Although initially efforts were primarily directed towards "input" or producer orientated traits, there are many advances to improve the quality and nutritional value of crops for human and animal consumption. These "output" traits have come to the fore in recent years through the promotion of "golden rice". Golden rice has the potential to overcome
Day, P. R. (1996) Genetic modification of proteins in food. Crit. Rev. Food Sci. Nutr. 36: S49-S67.
Munkvold, G. P., Hellmich, R. L. & Rice, L. G. (1999) Comparison of fumonisin concentrations in kernels of trangenic Bt maize hybrids and nontransgenic hybrids. Plant Dis. 83: 130-138.
Gianessi, L.P., An Economic Profile of the US Crop Protection Industry,
National Center for Food and Agricultural Policy, November 1995.
Oscarson, P. (2000) The strategy of the wheat plant in acclimating growth and grain production to nitrogen availability. J Exp. Bot. 51: 1921-1929.
Redenbaugh, K., Berner, T., Emlay, D., Frankos, B., Hiatt, W., Houck, C., Kramer, M., Malyj, L., Marineau, B., Rachman, N., Rudenko, L., Sanders, R., Sheehy, R. & Wixtrom, R. (1993) Regulatory issues for commercialization of tomatoes with an antisense polygalacturonase gene. In Vitro Cell. Dev. Biol. 29P:17-26.
Roca, W.M., 1989. Cassava production and utilization problems and their biotechnological solutions. In: A. Sasson
and V. Costarini (Editors), Plant Biotechnologies for Developing Countries. Technical Centre for Agriculture and Rural Co-operation and the Food and Agriculture Organisation of the United Nations, Rome, pp. 213-219.
