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European Corn Borer and Bacillus thuringiensis

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Is Bt the Best Option?

The advantage of these biotechnology improved crops is they now have resistance to ECB without the need of applied chemicals. However, at the same time, this technology has been the center of debate. There are opponents that question the ethics, food safety, and environmental impact of these crops. (Fig. 10)

Ethically, the practice of inserting genes from one organism into a completely unrelated organism (i.e. a gene from an animal into a plant) has raised concern with some (Schneider, 2002). Bt corn is an example of this practice where a gene from one organism (a soil bacterium) was inserted into another (a corn plant). Is it right to change the way organisms were naturally created? What will be the long term effects of putting foreign DNA material into the food supply? How will it affect feed for livestock? These are just three questions often asked by apprehensive consumers related to Bt corn and genetically engineered products.

A question related to the ethics of planting Bt corn revolves around who really benefits from growing this product. Is it the small family farms or the large farms? In a survey conducted by the University of Minnesota the majority of the farmers who responded stated that biotechnology would benefit large farms (Ramirez-Rocha and Hurley, 2004). What is the reason for this response? This could be attributed to the added cost associated with purchasing biotechnology enhanced seed or to the reduction in labor and chemicals seen as a result of using this new technology.

Food safety is another issue related to genetic engineering. StarLink corn, which at the time had been approved for animal feed, mistakenly found its way into U.S. food chains before being approved by regulatory agencies for human consumption. In this case, the specific CRY protein had shown potential for allergenicity due to its longer digestion times observed in the laboratory, a characteristic of some known allergens. Therefore, until further research had been conducted on the effects in humans, the product was released for animal feed only, which in the end was a mistake due to the difficulty in keeping grains separated.
 

Fig. 10: Example of a corn field under center pivot irrigation. (UNL, 2004)

Another food safety concern is that of antibiotic resistance (Segarra and Rawson, 2001). In the biotechnology process, antibiotic resistance markers (see the Gene Cloning 2: Making and Screening Gene Libraries lesson for more information) are used to identify the successful steps. Some consumers are concerned these same antibiotic resistance genes will somehow get transferred to bacteria and therefore, because of their resistance, people infected with these antibiotic resistant bacteria would have medical complications. Since those earlier days, scientists now use other markers in their experiments (1Transgenic Crops, 2004).

Finally, questions have been brought up as to the impact Bt corn could have on the environment. One of these concerns relates to how Bt corn affects non-target insects, such as the Monarch butterfly. One of the main questions surrounding this concern is if beneficial, non-target insect populations will decrease due to the presence of Bt corn. It is important to also ask what the effects are of Bt spray applications to traditional, non-Bt corn fields. For more information on the Monarch butterfly debate see Losey, et al., 1999 and 3Transgenic Crops, 2004.

A second environmental issue discusses how Bt inserted into plants affects the soil in which they are grown. Some studies have been conducted that look at the leakage of Bt toxin into the soil through the corn roots. It has been concluded that leakage from plant roots does occur, but more research is needed to confirm any adverse effects on soil microorganisms (4Transgenic Crops, 2004). Other studies have looked at how incorporation of above ground plant material into the soil affects the natural balance of microorganisms. Up to now, microbial populations in the soil do not appear to be effected by the incorporation of plant material containing Bt. (Mendelsohn, et al., 2003).

A third and final environmental concern is the development of ECB resistance to the Bt technology. ECB resistance develops when there is a higher number of resistant insects compared to susceptible. The resistant moths mate with the susceptible moths and the number of resistant insects increases. Currently, ECB resistance is not a problem but the potential for resistance to develop is a concern. This concern stems from the many acres planted to Bt corn and the ECB exposure to Bt over an extended period of time (2Transgenic Crops, 2004). Resistance develops without proper management to ensure susceptible ECB remain in the population. ECB resistance to Bt corn not only has implications for those farmers who have planted Bt corn on their land but also for those farmers who have not. Producers who choose to plant non-Bt corn may use a Bt insecticide spray to control ECB infestations. In the event of ECB resistance to Bt corn there would most likely be resistance to Bt sprays as well. For more on the implications of ECB resistance and management, see Witkowski, et al., 1997, 2Transgenic Crops, 2004, and Hunt and Echtenkamp, 2002.

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