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Symposium: Feeding the World in the Coming Decades

Research Needs to Improve Agricultural Productivity and Food Quality, with Emphasis on Biotechnology¹

Department of Molecular and Cell Biology, University of Cape Town, Cape Town, Rondebosch 7001, South Africa

²To whom correspondence should be addressed. E-mail: JAT{at}science.uct.ac.za.

	ABSTRACT

TOP ABSTRACT INTRODUCTION Biotic stress Abiotic stress Vaccine production in plants Food quality Conclusions LITERATURE CITED

 
Research into agricultural productivity, especially for crops in the developing world, should include resistance to plant viruses, fungi and the parasitic weed Striga. It must also include research into the development of resistance to Bacillus thuringiensis (Bt) toxin-expressing crops. Drought- and heat-tolerant crops, and those that can combat the problems of soil deficiencies, are required, and vaccine production in plants should be a high priority. Research into food quality should include the equivalent of "golden rice" in maize, the enhancement of the production of phytosterols and improved qualities of vegetable oils.

KEY WORDS: • biotic stress • abiotic stress • biotechnology

	INTRODUCTION

TOP ABSTRACT INTRODUCTION Biotic stress Abiotic stress Vaccine production in plants Food quality Conclusions LITERATURE CITED

 
The Green Revolution was remarkably successful in improving yields of food crops in many parts of the world. It was less successful, however, in Sub-Saharan Africa, where yields have hardly changed in 40 y and where cereal production per capita is steadily declining (1 ). It has been estimated that with current yields the projected shortfall of cereals will be 88.7 million tons by 2025 (2 ). Unless new technology is introduced to improve productivity, the subcontinent, and other parts of the developing world in similar situations, will experience major food shortages. One such technology that could fulfill some of these requirements is biotechnology.

This reports deals with the research that needs to be undertaken to improve agricultural productivity and food quality in developing countries, especially in Sub-Saharan Africa.

	Biotic stress

TOP ABSTRACT INTRODUCTION Biotic stress Abiotic stress Vaccine production in plants Food quality Conclusions LITERATURE CITED

 
Africa is home to a number of endemic plant viruses, including maize streak virus and African cassava mosaic virus. Zambia recently lost an entire annual crop to the latter virus. Scientists in South Africa have produced transgenic plants, expressing mutant-truncated replication-associated protein Maize streak virus genes, that are resistant to the virus. However, field trials are being hampered by the lack of suitable facilities. An international research program based at the Donald Danforth Center in St. Louis, Missouri, is aimed at developing transgenic cassava resistant to African cassava mosaic virus (personal communication, Dr. C. Fouquet, Donald Danforth Center).

Insect-resistant cotton expressing the Bacillus thuringiensis (Bt)³ toxin gene has been grown successfully by small-scale farmers in South Africa for a number of years. A recent independent study of the effects of these plantings came to the following conclusions (3 ):

• The average yield per hectare and per kilogram was higher for adopters than for nonadopters.
  
• The increases in yield and the reduction in chemical costs outweighed the higher seed cost of Bt cotton.
  
• There were heavy rainfalls in 1999 and Bt adopters experienced less decrease in yield than nonadopters.
  

However, research needs to be carried out into the development of insect resistance to the Bt toxin.

Fungal infections, both preharvest and postharvest, are a major problem in many parts of the developing world. In addition to crop spoilage or destruction, fungi can produce mycotoxins, such as aflotoxin, which can cause toxic hepatitis and liver and esophageal cancer in humans (4 ). Bt maize could help to alleviate these problems, especially among small-scale farmers who store their harvested crop for use throughout the year. If the kernels have not been subjected to insect damage, they will be less susceptible to subsequent fungal infection. Scientists have shown that the rotting of maize cobs due to fungal infection is greatly reduced in Bt maize (5 ,6 ). In addition, Bt-protected maize contains lower levels of fumonisin, a fungal toxin that can be fatal to livestock (7 ). However, research into fungus-resistant crops is lagging behind some of the other biotic stress problems.

Striga is a parasitic weed that grows on weak maize, rice and sorghum plants. It can be treated with a herbicide at doses of 5 g/hectare. However, that would require the host plants to be resistant to the herbicide. Research is being carried out on this problem, but it should have a higher priority than the current status.

	Abiotic stress

TOP ABSTRACT INTRODUCTION Biotic stress Abiotic stress Vaccine production in plants Food quality Conclusions LITERATURE CITED

 
The increase in desertification in Sub-Saharan Africa is cause for considerable concern. Transgenic crops that can tolerate some measure of drought and heat stress could alleviate some of the subcontinent’s lack of productivity. "For many developing countries even slight improvements in stress tolerance would significantly increase yields" (8 ). Africa is home to a large number of indigenous plants with a remarkable ability to withstand heat and desiccation. These so-called "resurrection plants" are found in deserts and grow in cracks in rocks. Scientists in South Africa are using one of these plants, the monocotyledonous Xerophyta viscosa, as a source of genes to develop drought- and heat-tolerant crops (9 ).

In most of Africa, virgin soils vary from acid to very acid, with pH values of 3.5–4.5. Cabbage production, for instance, requires the application of about 18 tons of lime per hectare. Acidity in the soil causes aluminum and manganese to become soluble, and this leads to toxicity. On the other hand, critical minerals such as molybdenum precipitate and are therefore unavailable to plants. In addition, levels of phosphate in the soil are often low. Again, using cabbage as an example, phosphate concentrations in the soil may be in the order of two parts per million (ppm), but this crop requires levels of 60–80 ppm and maize requires 40 ppm. Sources of phosphate are limited and expensive, and organic sources such as compost are usually too low in phosphate to be useful. Research into these problems should be viewed as a high priority.

	Vaccine production in plants

TOP ABSTRACT INTRODUCTION Biotic stress Abiotic stress Vaccine production in plants Food quality Conclusions LITERATURE CITED

 
Although not an agricultural or a food issue, the possibility of producing vaccines in plants should be included in a discussion of agricultural biotechnology in developing countries. The approach being taken by scientists in South Africa is not to produce edible vaccines but rather to use plants such as tobacco as "phactories" for vaccine production. This can be done either by producing transgenic plants expressing the viral protein to be used as the vaccine or by cloning the gene into a systemically infecting virus, such as Tobacco mosaic virus. The vaccine protein can be extracted from the tobacco plants and formulated into pills or capsules for oral ingestion. Using this route, the vaccine need not be as pure as if it were to be injected (personal communication, Prof. E. P. Rybicki, Department of Molecular and Cellular Biology, University of Cape Town). This approach will be suitable for viruses that invade the body via mucosal membranes, including such as human immunodeficiency virus and human papilloma virus, the leading cause of vaginal cancer in African women.

	Food quality

TOP ABSTRACT INTRODUCTION Biotic stress Abiotic stress Vaccine production in plants Food quality Conclusions LITERATURE CITED

 
According to the World Health Organization, 250 million children worldwide are at risk from vitamin A deficiencies, and 10 million people face illness and death. Many of these will experience impaired vision, decreased immunity and protein malnutrition because vitamin A affects the absorption and use of amino acids. "Golden rice," which carries genes from the daffodil, produces beta-carotene, which can be converted by a potential of 2.4 billion people who eat rice as their staple diet into vitamin A (10 ). What other developing countries now need is "golden maize."

Iron deficiency is another worldwide problem in developing countries, where 3.7 billion people, especially women, develop anemia and childbirth complications. "Golden rice" addresses this problem because it also contains genes from the French bean, which boosts iron content, and another gene that counteracts the effects of phytic acid, a substance found in rice that inhibits the body’s ability to absorb iron (10 ). The proteins produced by these genes are stable even after cooking. Again, other developing countries need these genes incorporated into maize.

Cardiovascular disease, which is linked to high levels of dietary cholesterol, is becoming ever more prevalent, in both developed and developing worlds. It is known that plant sterols (phytosterols) can reduce cholesterol in humans by 10–15% due to interference with cholesterol absorption in the gastrointestinal tract. Plant sterols are not currently available in adequate quantities in the foods we eat, and scientists are actively engaged in increasing the phytosterol content of several grains (11 ).

Vegetable oils are another example of how biotechnology can improve the quality of a food product. Canola and soybeans, the source of most of the cooking oil in the Western world, often contain trans-fatty acids, which may increase the risks of heart disease. Genetically modified varieties that are free of these acids are being evaluated for commercial viability. Furthermore, unsaturated fatty acids are healthier than saturated fatty acids. Concentrations of oleic acid, an unsaturated fatty acids, have been increased from 25% to 85% in the seeds of genetically modified varieties (12 ).

	Conclusions

TOP ABSTRACT INTRODUCTION Biotic stress Abiotic stress Vaccine production in plants Food quality Conclusions LITERATURE CITED

 
It is clear that a great deal of biotechnological research is being conducted into the improvement of agricultural productivity and food quality, for both developing and developed countries. However, farmers will not plant crops with such improvements unless they are linked to increased yields and increased profits. Scientists undertaking this research need to bear this in mind and ensure that the plants they produce do indeed provide improved yields and profits.

	FOOTNOTES

 
¹ Presented as part of the annual symposium of the Society for International Nutrition Research (SINR). The title of the symposium was "Feeding the World in the Coming Decades" and was given at the 2002 Experimental Biology meeting on April 21, 2002. The symposium was supported in part by The American Society for Nutritional Sciences, The Rollins School of Health Sciences of Emory University, The International Food Policy Research Institute (IFPRI) and by an educational grant from the Archer Daniels Midland Company. Guest editors for the symposium were Lawrence Haddad, Food Consumption and Nutrition Division, IFPRI, Washington, D.C. and Reynaldo Martorell, Department of International Health, Rollins School of Public Health, Emory University, Atlanta, GA.

³ Abbreviation used: Bt, Bacillus thuringiensis.

	LITERATURE CITED

TOP ABSTRACT INTRODUCTION Biotic stress Abiotic stress Vaccine production in plants Food quality Conclusions LITERATURE CITED

 

1. Conway, G. (1997) The Doubly Green Revolution: Food for All in the Twenty-First Century 1997 Penguin Ithaca, NY. .

2. Dyson, T. (1999) World food trends and prospects for 2025. Proc. Natl. Acad. Sci. U.S.A. 96:5929-5936.[Abstract/Free Full Text]

3. Ismael, Y., Bennett, R. & Morse, S. (2001) Can farmers in the developing countries benefit from the modern biotechnology? Experience from Makhathini Flats, The Republic of South Africa. Crop Biotech. Brief 1(5)(ISAAA publication)..

4. Marasas, W. F. O., Jaskiewicz, K., Venter, F. S. & Van Schalkwyk, D. J. (1988) Fusarium moniliforme contamination of maize in oesophageal cancer areas in the Transkei. S. Afr. Med. J. 74:110-114.[Medline]

5. Munkvold, G. P., Hellmich, R. L. & Showers, W. B. (1997) Reduced fusarium ear rot and symptomless infection in kernels of maize genetically engineered for European corn borer resistance. Phytopathology 87:1071-1077.[Medline]

6. Munkvold, G. P., Hellmich, R. L. & Rice, L. R. (1999) Comparison of fumonisin concentrations in kernels of transgenic Bt maize hybrids and nontransgenic hybrids. Plant Dis. 83:130-138.

7. Norred, W. P. (1993) Fumonisins - Mycotoxins produced. J. Toxicol. Env. Health B 38:309-328.

8. Hoisington, D., Khairallah, M., Reeves, T., Ribaut, J.-M., Skovmand, B., Taba, S. & Warburton, M. (1999) Plant genetic resources: What can they contribute toward increased crop productivity?. Proc. Natl. Acad. Sci. U.S.A. 96:5937-5943.[Abstract/Free Full Text]

9. Mundree, S. G. & Farrant, J. M. (2000) Some physiological and molecular insights into the mechanisms of desiccation tolerance in the resurrection plant Xerophyta viscosa Baker. Rychter, A. M. Locy, R. D. Cherry, J. H. eds. Plant Tolerance to Abiotic Stresses in Agriculture: Role of Genetic Engineering 2000:201-222 Kluwer Academic Publishers Netherlands. .

10. Gura, T. (1999) New genes boost rice nutrients. Science (Washington, D.C.) 285:994-995.[Free Full Text]

11. Kishore, G. M. & Shewmaker, C. (1999) Biotechnology: enhancing human nutrition in developing and developed worlds. Proc. Natl. Acad. Sci. U.S.A. 96:5968-5972.[Abstract/Free Full Text]

12. Mazur, B., Krebbers, E. & Tingey, S. (1999) Gene discovery and product development for grain quality traits. Science (Washington D.C.) 285:372-375.[Abstract/Free Full Text]

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