|
Items in cart [1] |
Questions? Call 888-624-8373 |
| ||||||||||||
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 9
2
Opportunities for Applying
Biotechnology1
T
he world population has increased from 2.5 billion in 1950 to 6.7
billion today and is estimated to reach almost 9.2 billion by 2050
(United Nations, 2007). With that growth comes the challenge of
producing enough food to meet the demands of the world’s people and
an even greater challenge of producing it in a way that conserves the
biodiversity and other natural resources on which societies depend. One
estimate is that agricultural production will need to increase by 50 percent
by 2020 to meet the world’s demand for food (Shah and Strong, 1999).
Technological innovation has helped to ease some problems posed by
population growth; over the last 50 years, agricultural productivity has
doubled worldwide and even tripled in developing economies (Doering
et al., 2002). During the 20th century, the Green Revolution drew on the
research of conventional plant breeders to develop higher-yielding crops
that were successful in increasing the global food supply. However, the
new crop varieties introduced in the Green Revolution created depen-
dence on additional farming inputs and created some new environmental
problems. Today, with finite acreage of high-quality agricultural land on
which to grow food (Tilman et al., 2001), biotechnology has emerged as a
1 Since the October 2004 workshop, the agricultural biotechnologies cited in the workshop
have progressed rapidly, yet the opportunities for their application are still relevant and
have yet to be fulfilled. In a forthcoming National Research Council report, Emerging Tech-
nologies to Benefit Farmers in Sub-Saharan Africa and South Asia (2008), several promising appli-
cations of biotechnology are described to address the problems that small-holder farmers
encounter in developing countries.
OCR for page 10
0 GLOBAL CHALLENGES FOR AGRICULTURAL BIOTECHNOLOGY
potential tool for overcoming the current limitations on food production.2
Many have asked whether biotechnology can live up to its promise and
whether it will also generate new dependences and problems.
This chapter describes some of the opportunities for using biotechnol-
ogy in an agricultural and environmental context as discussed by partici-
pants in the workshop, and Box 2-1 provides a summary of opportunities
for applying biotechnology. Although increasing crop yields by over-
coming agronomic and environmental constraints is the most commonly
recognized target of biotechnology, there are many other possibilities for
developing useful applications, such as improving the sustainability of
farming processes, developing more-nutritious foods, improving water
quality, and identifying useful genetic material in nature. The workshop
consisted of a series of presentations by lead speakers followed by com-
mentary and shorter presentations by panels of experts. The presentations
focused on specific ways in which biotechnology could address a problem
or constraint, and the discussions examined the needs of the developing
world relative to the potential of biotechnology.
IMPROVING CROP PRODUCTIVITY
Biotechnology is the application of scientific and engineering prin-
ciples to the processing or production of materials by biological agents
to provide goods and services (NRC, 2002a). Agricultural biotechnology
encompasses a growing list of techniques that range from simple probes
to determine whether an individual plant or animal is carrying a spe-
cific gene to measurement of the activity of all an organism’s genes (its
genome) simultaneously. One technique common in agricultural biotech-
nology is the integration of a gene from one species into the genome of
another. This technique is commonly referred to as genetic engineering,
and the resulting product is described as transgenic (having a foreign
gene). Genetic engineering allows novel characteristics to be introduced
into a plant; this could not generally be accomplished with standard
breeding techniques.
Although some commercial products of genetic engineering are well
known and were the focus of some of the presentations, the power of
biotechnology goes far beyond the ability to make transgenic crops. Being
able to recognize the characteristics of an individual organism on the
basis of its genetic makeup and having the power to mimic the biological
2 By 2007, a total of 23 countries were growing transgenic crops. In order of acreage, they
include the United States, Argentina, Brazil, Canada, India, China, Paraguay, South Africa,
Uruguay, Philippines, Australia, Spain, Mexico, Colombia, Chile, France, Honduras, Czech
Republic, Portugal, Germany, Slovakia, Romania, and Poland (ISAAA, 2008).
OCR for page 11
OPPORTUNITIES FOR APPLYING BIOTECHNOLOGY
Box 2-1
Selected Opportunities for Applying Biotechnology
Crop Productivity
Overcoming biotic stresses
Insects
Weeds
Overcoming abiotic stresses
Soil fertility
Heat stress
Drought stress
Inefficiency of resource use
Nutritional Value of Crops
Enhancing vitamin concentrations
Enhancing mineral concentrations
Enhancing protein content
Plant-Made Pharmaceuticals
Vaccines
Protein therapeutics
Improved Food Security
Reducing post-harvest loss
Reducing risks to food production
Alternative uses
Biodiversity
Engineering safeguards to protect existing biodiversity
Preserving biodiversity
Natural Resource Conservation
Renewable energy
Phytoremediation
activity of an organism by using its own cellular and molecular machinery
are capabilities that allow us to deepen our understanding of all organ-
isms. That knowledge has led to the development of some practical tools,
examples of which were identified by workshop participants and are
listed in Box 2-2. Ganesh Kishore, of DuPont Agriculture and Nutrition,
provided an overview of some available biotechnologies to improve crop
productivity, and the presentation provided context for shaping subse-
quent discussions.
OCR for page 12
GLOBAL CHALLENGES FOR AGRICULTURAL BIOTECHNOLOGY
Box 2-2
Some Tools of Biotechnology (Apart from Genetic Engineering)
• Marker-assisted breeding uses conventional breeding techniques
informed by specific genetic sequences, or “markers,” that segregate
according to particular traits. Markers speed up breeding programs by
allowing researchers to determine, early in the life of a progeny, whether
the traits they hoped to combine from two organisms are present simply
by checking for the presence of the markers.
• Tissue culture is used in clonal propagation of plants for which
sexual breeding has proved inefficient. It has been important for reproduc-
ing crops used across the African continent, including oil palm, plantain,
banana, date, eggplant, pineapple, rubber tree, cassava, maize, sweet
potato, yam, and tomato.
• Cloning and in vitro fertilization allow the manipulation of germ
cells for animal-breeding programs, genetic-resource conservation, and
germplasm enhancement.
• Gene profiling or association mapping tracks the patterns of
heritability of variations (alleles) of many genes. The quantitative trait loci
(QTLs) collectively contribute to complex plant traits, such as drought tol-
erance and robust seed production, and understanding of the groupings
of QTLs provides insights into how genes work in concert to produce a
particular characteristic.
• Metabolomics provides a snapshot of all the metabolites being
produced in a plant cell at any given time under different environmental
conditions.
Overcoming Biotic Stresses to Crops
Insects and weeds can cause substantial crop losses. Kishore described
the first generation of commercial transgenic products, the pest-protected
and herbicide-tolerant crops that were first introduced in the United
States. In one example, as young plants of herbicide-tolerant soybeans
emerge, the field is treated with glyphosate; this kills the weeds, but
the crops tolerate the herbicide. The benefits of the method include the
OCR for page 13
OPPORTUNITIES FOR APPLYING BIOTECHNOLOGY
savings in time, labor, and energy involved in managing weeds and the
ability to avoid tillage, which causes soil drying and erosion. In a second
example, pest-protected crops have been genetically engineered to pro-
duce a bacterial toxin, an insecticide derived from Bacillus thuringiensis
(Bt), which kills lepidopteran pests of corn and cotton. According to
Kishore, many U.S. farmers did not recognize how much the European
corn borer affected both the productivity and the quality of their crop
until they cultivated Bt corn, compared the resulting yields, and saw how
much they had been losing.
Transgenic crops have now been widely planted in the United States,
China, Canada, Argentina, Brazil, and South Africa and are at varying
stages of evaluation or adaptation in many other countries. Some major
crops protected against biotic constraints include transgenic maize, cot-
ton, and soybean, but, as noted in the workshop, other transgenic crops
are under development. Participants noted in particular the efforts to
develop weed-resistant plants and to insert Bt genes into pro-vitamin A
white starchy sweet potatoes to make them resistant to weevils.
Overcoming Abiotic Stresses to Crops
Although herbicide-tolerant and Bt crops are the most common types
of transgenic crops, there is great interest in introducing other charac-
teristics into plants to make them more productive in poor agronomic
conditions.
Nutrient-Poor Soil
Soil degradation affects one-fourth of agricultural land worldwide
(GEF, 2003) and is one of the most important limitations on agricultural
production in the developing world. The African landscape is plagued by
weathered soils and poor soil fertility (Holden, 2006). Although investment
in improving soil fertility is needed, Kishore described how researchers
at such companies as DuPont have used plants—for example, corn and
arabidopsis—to produce transgenic plants with improved responsive-
ness to nitrogen. Crops that have been genetically engineered to more
efficiently fix nitrogen, and thus reduce the need for external inputs of
fixed nitrogen, could enable farmers to lower their production-related
input costs while improving crop performance.
Heat and Drought Stress
Water security is projected by the United Nations Population Fund as
one of the top global issues in the 21st century (UNFPA, 2002). More than
OCR for page 14
4 GLOBAL CHALLENGES FOR AGRICULTURAL BIOTECHNOLOGY
a half-billion people live in countries defined as water-stressed or water-
scarce, and by 2025 that figure is expected to increase to 2.4-3.4 billion
(UNFPA, 2002). Drought-resistant transgenic crops could be useful in alle-
viating the demand for water in agriculture. Kishore described DuPont’s
work on corn varieties that maintain high yields under drought condi-
tions and the development of drought-tolerant millet and sorghum, two
staple crops; drought tolerance could have a large effect on agricultural
productivity in Africa. It is unclear how well the technology will work
under a multitude of field conditions—influenced by factors such as
regional and geographic differences—and whether two or more types of
stress (such as stress caused by heat and stress caused by drought) will
have a compound effect on productivity.
Salinity
Salt tolerance was mentioned by workshop participants as useful in
the developing world. Soils are often poor in quality because of salinity,
and salt tolerance in crops such as rice and other cereals and vegetables
would allow saline soils to be used more productively. Mariam Sticklen,
of Michigan State University, described her work on a barley gene that
confers salt tolerance in transgenic oats.
Efficiency of Resource Use
Multiple lines of research are being conducted to find the genetic basis
of a plant’s ability to efficiently use resources, such as sunlight and nutri-
ents. Kishore described research to improve the plants’ ability to utilize
whatever nutrition is available, starting with sunlight, carbon dioxide,
and nutrients in soil. Beans and high-yield rice are two crops being exam-
ined for efficiency of resource use.
IMPROVING THE NUTRITIONAL VALUE OF CROPS
Advances in biotechnology have not only shown a potential for
improving food production but have broadened the spectrum of available
agricultural products (FAO, 2000; Dargie, 2001). Some 2-3 billion people
suffer from widespread micronutrient and protein deficiencies, and mal-
nutrition accounts for about 50 percent of deaths among children under
the age of 5 (WHO, 1998; Micronutrient Initiative, 2008). The challenge
will be to provide them with adequate nutrition.
Food crops that are either conventionally bred or genetically engi-
neered for enhanced nutritional value can be used to alleviate micro-
nutrient deficiencies in the developing world (Bouis, 2002; Toenniessen,
OCR for page 15
OPPORTUNITIES FOR APPLYING BIOTECHNOLOGY
2002). High-carotenoid canola and “golden” rice have been engineered
to combat vitamin A deficiency (Guerinot, 2000; Ye et al., 2000) that is the
single most important cause of preventable child blindness in developing
countries and which affects the health and survival of at least 254 million
“at risk” children of preschool age (WHO, 1995). Benjavan Rerkasem,
of Chiang Mai University in Thailand, noted that lysine-enriched maize
hybrids developed in China are being successfully grown by poor farmers
there and in remote border areas in Vietnam and Laos (Prasanna et al.,
2001). Crops are also being biofortified with micronutrients such as iron,
iodine, vitamin A, and folic acid; and staple crops, such as sweet potatoes,
are being enhanced with zinc (Pollack, 2003; HarvestPlus, 2008). Research-
ers at DuPont are engineering an increase in the nutrient density of veg-
etable proteins by increasing biologically available phosphates in grains,
increasing several essential amino acids, and improving the oil and starch
components of seeds. Those are just a few examples of work being done
around the world. Dietary diversity, biofortification, and supplementation
are other ways to deal with nutritional deficiencies.
In addition to incorporating novel genes into plants, biotechnology
can be used to identify genes in native plant populations that could
improve human health and nutrition. Researchers with the Brazilian
Agricultural Research Corporation (Embrapa), part of the Ministry of
Agriculture, have looked for diversity in the carbohydrate and carot-
enoid content of cassava and discovered a sugary cassava with both
a higher sugar concentration and a different starch structure. Those
researchers also discovered “golden cassava,” which contains high con-
centrations of β-carotene, lycopene, and lutein. Carotenoid genes of
golden cassava could be bred into other cassava varieties to improve
nutritional quality.
IMPROVING FOOD SECURITY
Food security involves more than adequate production in the field.
The timing of the harvest, availability of food throughout the year, flex-
ibility in the use of a crop, and ability to store food are important compo-
nents of food security. Biotechnology can reduce the risk of variability in
food availability in several ways.
Post-Harvest Losses
Post-harvest losses can be enormous in developing countries. Between
field and plate, reports quote losses of 10–100 percent in some fruits and
vegetables in Africa. If genetic resistance to post-harvest pests and fungi
are built in, this can increase the ability of farmers to store crops and crops
OCR for page 16
GLOBAL CHALLENGES FOR AGRICULTURAL BIOTECHNOLOGY
stand a better chance of making it to the market. Biotechnology can also
facilitate the preservation of nutrients from farm to plate. For example,
cassava juice is high in beta-carotene, but it quickly loses potency when
stored. Embrapa researchers have worked with Amazon natives to devise
a convenient powder of cassava juice that can be reconstituted into vita-
min-rich juice.
Those technological solutions might not, however, be able to compen-
sate for the lack of infrastructure, according to Bongiwe Njobe, director
general of South Africa’s Department of Agriculture. She described a
situation with maize production in Zambia where the absence of roads
inhibited the transportation and distribution of maize before the rainy
season. Once the rain set in, transport of the maize crop to markets was
lost, and the country found itself vulnerable.
Risks to Food Production
Biotechnology can address food security issues by reducing risks to
food production in two ways: by increasing the reliability of production
and by smoothing supply and demand in rural markets. After harvest in
rural areas, there can be a large drop in prices; a severe decrease in the
market price of maize in Africa can have a devastating effect on farm fam-
ilies. Anything that can be done to increase storability or to smooth pro-
duction and consumption throughout the year will have highly beneficial
effects on family health, well-being, and opportunities. Transgenic crops
can potentially have a sizable effect on smoothing production, according
to Kishore, who described Monsanto’s work on genes that confer toler-
ance to chilling-injuries. Cold-tolerant crops could help to increase the
optimal timeframe of a crop’s production and allow farmers to choose
crops that sell later in urban markets and to wait until markets are more
favorable for their sale. If poor farmers were able to get seeds into a field
3-8 weeks earlier, they would have more flexibility to escape late-season
plant diseases, drought, and pest attacks. They would also have oppor-
tunities for staggering crops and planting multiple crops to extend the
timeframe when farmers can bring crops to market.
Alternative Uses
Biotechnology can increase the availability of alternative types of
crops. Embrapa researchers have developed cassava varieties that meet
the specific needs of local communities. For example, cassava has been
engineered to produce better glucose syrup and used as beer precur-
sors. Another example of an alternative crop use is the production of
OCR for page 17
OPPORTUNITIES FOR APPLYING BIOTECHNOLOGY
plant-administered medications. Vaccines that are based on edible plants3
may offer the developing world a locally grown, more stable, and less
expensive production method compared to conventional pharmaceutical
production (Arntzen, 1997a,b; Tripurani et al., 2003).
Increasing the reliability of production creates the possibility for other
mechanisms—such as the development of financial systems (including
savings accounts, financing of agriculture, and financing of agricultural
inputs) and other infrastructure—to stabilize a rural economy and reduce
both the risk of crop failure and the financial risk taken by farmers in
producing food.
PROTECTING AND PRESERVING BIODIVERSITY
Biodiersity is a term used to describe the array of the world’s species,
the genetic variability in and among populations of a species, and the
distribution of species among local habitats, ecosystems, landscapes, and
whole continents or oceans (NRC, 1999). The number of naturally occur-
ring species of plants and animals tends to be higher in many developing
countries of the tropics than of industrialized countries of temperate cli-
mates. Preserving that biodiversity is important for maintaining the func-
tioning of natural ecosystems, which provide part of the base of natural
resources, such as water and pollinators, that supports such human activi-
ties as farming. The biodiversity in natural ecosystems is also a source of
genetic variability that is useful in crop development, as mentioned in a
presentation by Luiz Carvalho, of Embrapa in Brazil. For example, genes
that confer resistance to diseases can often be found in the wild relatives
of domesticated crops, and these genes may sometimes be used by con-
ventional breeders and molecular breeders to enhance the characteristics
of crops. The discovery of diversity in carbohydrate and carotenoid types
in cassava is another example of finding valuable properties in plants that
can improve human nutrition and health.
The role of biodiversity in natural and managed ecosystems has mul-
tiple aspects. For example, some participants in the workshop criticized
industrialized models of agriculture and cited how genetically narrow
monocultures place crops and agricultural systems at risk for devasta-
tion by disease. They advocated for more diverse agricultural production
farming systems and greater genetic diversity in crops.
Some in the workshop suggested that applying new agricultural bio-
technologies without disrupting the biodiversity in many developing
3 There are concerns about quality control, potential drug overdose, and other potential
risks associated with the use of food crops to produce drugs (Graham, 2000; Coghlan,
2005).
OCR for page 18
GLOBAL CHALLENGES FOR AGRICULTURAL BIOTECHNOLOGY
countries presents a serious challenge. The capacity does not exist, they
believe, to look critically at what may or may not be beneficial in particu-
lar settings.
Several workshop participants expressed their concern about how
the introduction of transgenic crops would affect gene flow, agricultural
productivity, and the natural environment. Rerkasem brought up the
example of weedy rice, believed to be a natural hybrid of cultivated
and wild rice species or a result of the de-domestication of cultivated
rice (IRRI, 2008). The flourishing of weedy rice in Thailand’s central rice
bowl reduced yields of cultivated rice, illustrating the risk of genetic
exchange between cultivated and wild varieties and how they can have
unpredictable outcomes. According to Rerkasem, because gene flow is
unpredictable even in wild species, mechanisms of addressing biosafety
concerns will need to be considered before transgenic crops are moved
from the laboratory to the field to ensure that they do not reduce natural
biodiversity.
Workshop participants described research that is under way to
develop safeguards to block gene flow; according to some, the technology
already exists to prevent gene escape. Richard Meagher, of the University
of Georgia, described plants that can produce sterile pollen or seeds (for
example, sterile because of thiamine deficiency) and plants that can be
engineered for male or female sterility. Sticklen mentioned that another
method to block gene flow is to transform new genes into chloroplasts
rather than into nuclear DNA; chloroplasts are maternally inherited in
most flowering plants, and the new genes will not be found in pollen.
Biotechnology can be used for more than the creation of genetically
engineered crops: it can be used to preserve biodiversity and aid in genetic
resource conservation efforts. Carvalho suggested that surveys are needed
to determine the status of existing biodiversity, evaluate its value and
importance, and identify endangered species and genes. On the basis
of the survey results, he argued, measurable targets for the sustainable
use and conservation of various species could be set. An overarching
challenge is the lack of human capacity on the ground to monitor what
happens to biodiversity when new living systems are introduced, what
happens in the long term, whether there are benefits, and whether there
are serious disruptions of ecological life.
Work is under way in several countries to characterize indigenous
plant varieties and animal breeds with biotechnologies to document and
safeguard biodiversity. For instance, Carvalho described an Embrapa
program in native Krahos communities in Brazil that had lost their
traditional plant varieties and faced community collapse due to lack of
food. Embrapa, which had been collecting samples of biodiversity in the
OCR for page 19
OPPORTUNITIES FOR APPLYING BIOTECHNOLOGY
region, had the traditional landraces in its gene bank and was able to
return the original landraces to the Krahos. Embrapa researchers then
teamed up with the Krahos to rescue traditional knowledge associated
with the Krahos agricultural system, to educate and train the residents
in other agricultural methods, and to collaborate with them to organize
and maintain a germplasm collection. The use of field-plot germplasm
collections and in vitro tissue-culture methods gave residents a powerful
tool to preserve regional biodiversity. This example illustrates how the
techniques of biotechnology have been used to conserve biodiversity and
the cultural heritage of native people.
ENHANCING NATURAL RESOURCE CONSERVATION
Agricultural biotechnology can have secondary effects that enhance
natural resource conservation and protect the environment. By devel-
oping drought-tolerant crops, researchers can help farmers to conserve
water resources. Crops that are genetically engineered to produce Bt toxin
require less spraying of pesticides, and reduction in spraying reduces the
potential environmental harm caused by pesticides. Agriculture accounts
for more than 30 percent of global greenhouse gas emissions (FAO, 2006a);
however, herbicide-resistant crops promote no-till cultivation practices
which help to reduce soil erosion, emissions of greenhouse gases, and
carbon loss (Robertson et al., 2000; Lal et al., 2004; Zheng et al., 2004).
Renewable Energy
Workshop participants noted that biotechnology could play a major
role in addressing the world’s energy and resource needs in the future.
Trees that are genetically engineered to grow faster could help to meet the
world’s demand for industrial wood and potentially reduce the need to
harvest trees from natural forests. New plastics made from biodegradable
plant polymers may one day provide an environmentally safer alterna-
tive to traditional plastics made from fossil fuel. Global energy demands
are forecasted to increase by 40 percent in the next 20 years (EIA, 2003).
If energy demand is met by fossil fuel use, much more carbon dioxide
will be produced. Agricultural products can be engineered to provide
fuel alternatives in the form of biodiesel and biofuel: Sticklen described
research to engineer rice straw, a major environmental contaminant in
developing nations, so that it is biologically broken down into useful
alcohol-based fuels.
OCR for page 20
0 GLOBAL CHALLENGES FOR AGRICULTURAL BIOTECHNOLOGY
Phytoremediation
Many populations are regularly exposed to toxic substances, such as
arsenic and mercury, and thus live in environments that are deleterious
to their health. In Bangladesh alone, an estimated 57 million people—44
percent of the population—are at risk of exposure to toxic concentrations
of arsenic in drinking water (UNESCO, 2008). About 6 million people in
the Amazon are at risk of methylmercury poisoning from the nearly 5,000
tons of mercury deposited in tributaries as a result of gold mining (Veiga,
1997; Harada et al., 2001). Many land and water resources are contami-
nated on a global scale and cannot be remediated by physical methods,
but biotechnology-based alternatives could provide solutions to problems
of environmental contamination.
For phytoremediation, Meagher described one system for cleaning
up the environment that uses native plants to degrade organic pollut-
ants, such as trichloroethylene and polycyclic aromatic hydrocarbons, and
process them into less harmful molecules. Elemental pollutants—such as
arsenic, mercury, and radionuclides—cannot be readily metabolized or
broken down; however, plants can extract, concentrate, and accumulate
those pollutants from the soil for aboveground harvest and disposal.
Determining which plants to exploit for that purpose and finding safe dis-
posal sites is part of the research. The plants used to accumulate the pol-
lutants would ideally be nonfood plants—something inedible—to prevent
accidental poisoning and would grow between productive food crops so
that farmers could maintain land productivity.
Genetically engineered phytoremediants have already shown promis-
ing results in initial field tests. The first field trials of a native hybrid accu-
mulator of nickel have successfully extracted nickel. Researchers have
also successfully used RNA interference to inhibit plants from converting
a form of arsenate into another form that collects in roots; such inhibition
allows plants to transport arsenic to their shoots and leaves, which can
then be harvested. Cottonwood trees are among the several species that
have been engineered to grow in mercury-contaminated soil and remove
high concentrations of mercury.
