Could Biotech Cotton Seeds Feed the Planet?
Excerpted by Peacework intern Rebecca Recant from an article by Ganesan Sunilkumar, LeAnne M. Campbell, Lorraine Puckhaber, Robert D. Stipanovic, and Keerti S. Rathore, "Engineering Cottonseed for Use in Human Nutrition by Tissue-Specific Reduction of Toxic Gossypol" in the Proceedings of the National Academy of Sciences on November 16, 2006.
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Cotton is grown in over 80 countries and is a cash crop for over 20 million farmers in developing countries in Asia and Africa, where malnutrition and starvation are rampant. An attribute of cotton not widely recognized is that for every 1 kg of fiber, the plant produces about 1.65 kg of seed. This makes cotton the third largest field crop in terms of edible oilseed tonnage in the world. By weight, cottonseed is 21% oil, and 23% a relatively high-quality protein. Global cottonseed production can potentially provide the protein requirements for half a billion people per year.
However, the ability to use this nutrient-rich resource for food is hampered by the presence of toxic gossypol. Thus, gossypol-free cottonseed would significantly contribute to human nutrition and health, particularly in developing countries, and would help meet the requirements of the predicted 50% increase in the world population in the next 50 years.
Attempts were made to meet this objective by developing so-called ''gland-less cotton'' in the 1950s by conventional breeding techniques. However, the glandless varieties were commercially unviable because of the increased susceptibility of the plant to insect pests due to the systemic absence of glands that contain gossypol and other protective organic chemicals.
However, an RNA interference (RNAi) approach can silence precise genes, thus eliminating gossypol from the seed while retaining a full complement of the protective substances in the rest of the plant for maintaining its defensive capabilities against insects and diseases. Furthermore, the low-gossypyl cottonseed trait is stable and successfully transmitted to progeny [in the lab].
The seeds in the second generation produced an average gossypol value of 190 parts per million (the UN Food and Agriculture Administration safety guidelines permit up to 600 parts per million). These results demonstrate the feasibility of a targeted RNAi-based approach.
This research opens up a new frontier in the use of genetic manipulation to enhance global food supply. It raises the possibility of using a similar approach to eliminate harmful compounds from other potential food sources, including Lathyrus sativus, a hardy tropical/subtropical legume that could serve as an important source of nutrition-rich food if it were not for the presence of a neurotoxin that appears in dangerous concentrations when the crop is grown under drought conditions. This technique could also improve the safety of other crops as well.
An approach based on the removal of naturally occurring toxic compounds from the edible portion of the plant not only improves food safety but also provides an additional and potentially extraordinary means to meet the nutritional requirements of the growing world population without having to increase either crop yields or acreage planted. Thus, cotton, which has served the clothing needs of humanity for millennia, has the potential to make a significant contribution to our nutritional requirements as well.
