The Importance of Common Bean
Nutritionists characterize the common bean as a nearly perfect food because of its high
protein content and generous amounts of fiber, complex carbohydrates, and other dietary
necessities. A single serving (1 cup) of beans provides at least half the US Department of Agriculture's recommended
daily allowance of folic acid—a B vitamin that is especially important for pregnant
women. It also supplies 25 to 30 percent of the recommended levels of iron and meets 25
percent of the daily requirement of magnesium and copper as well as 15 percent of the
potassium and zinc.
The common bean was domesticated more than 7,000 years ago in two centers of
origin—Mesoamerica (Mexico and Central America) and the Andean region. Scientists
believe dry beans, along with maize, squash, and amaranth, probably began as weeds in
fields planted to cassava and sweet potatoes in Central America. Over the millennia,
farmers grew complex mixtures of bean types as a hedge against drought, disease, and pest
attacks. This process has produced an almost limitless genetic array of beans with a wide
variety of colors, textures, and sizes to meet the growing conditions and taste
preferences of many different regions.
Beans are grown from sea level to more than 3,000 meters chiefly by small farmers with
average land holdings of less than 1 hectare, without irrigation, and using little or no
fertilizers or pesticides. Much of the bean production in Latin America and sub-Saharan
Africa, where three-quarters of the crop is grown, takes place on steep, erosion-prone
slopes with low soil fertility.
In recent years the common bean has found an important market niche in burgeoning Latin
America cities, where millions of rural poor have migrated, seeking jobs to support their
families. With about 70 percent of Latin America’s population now concentrated in
urban centers, bean farmers are finding new sources of cash income.
Latin America is the most important bean producing region, its 8 million hectares
accounting for nearly half of global output. Beans are the fourth most important source of
protein in tropical America and surpass two popular regional root crops—potato and
cassava—as a source of calories. Throughout the region the common bean is known as
the "poor man's meat." Because there is no cheaper source of protein, per capita
consumption of beans is high in very poor countries, such as Nicaragua (with 22.5
kilograms per capita per year), and in poorer regions of higher income countries, such as
Northeast Brazil (with 18.5 kilograms per year).
Dry beans were introduced in sub-Saharan Africa several centuries ago by Portuguese
traders. Today, the crop is a vital staple on this continent, providing the main source of
dietary protein for more than 70 million people. Dry beans are raised mostly by women for
subsistence and the market on more than 3.5 million hectares, accounting for a quarter of
global output. Production is concentrated in densely populated eastern Africa, the lakes
region, and highlands of southern Africa.
Research for Development
Challenge
Given current trends in population growth and bean consumption, demand for this crop in
Latin America and sub-Saharan Africa can be expected to grow at unprecedented levels well
into the next century. How can countries in those regions meet the demand, and how can the
low-income farmers who grow most of the bean crop benefit in the process? These are the
main questions that our agenda of bean research and development must address.
In most bean-growing environments, land and labor scarcity severely limits the
possibilities for increasing production by expanding the area planted. Moreover, most of
this expansion would take place in ecologically fragile areas, incurring high
environmental costs. It is thus vital that farmers gain the means to raise bean yields per
hectare on the land already cultivated. And they must be able to do so without necessarily
using heavy doses of purchased inputs, since most bean growers cannot afford these.
Against difficult odds Latin America has achieved notable progress in raising bean
productivity over the last decade or so. With the aid of new technology, many rural
communities have managed to intensify production, thus strengthening local food security
and raising incomes through bean sales to local and urban markets. But to secure and
expand those gains, bean research and development must persist in confronting a formidable
array of constraints--including depressed yields, shifting disease and pest problems, and
the stubborn physical constraints of infertile soils and drought.
Such research is a matter of particular urgency in sub-Saharan Africa, where bean
yields have increased only modestly in recent years, while the area under production has
actually declined. Rates of increase in bean production on this continent still lag behind
population growth (which at 2.8 percent a year is among the highest in the world), with
the result that growers are unable to keep pace with market demand. Because of the
importance of beans in the African diet, the nutritional consequences of this gap are
truly alarming.
CIAT scientists are convinced that new bean cultivars with higher yields, multiple
disease resistance, and greater tolerance to drought and low soil fertility will enable
farmers to increase bean productivity and achieve greater yield stability. New production
technology, together with the bean crop's wide adaptability, will help it remain an
attractive option for small-farmer cropping systems.
Genetic Resources
One potent source of solutions to problems in bean production is the vast array of
genetic diversity available for research and development in the world Phaseolus
collection maintained at CIAT headquarters (GRU) in trust
for the Food and Agriculture Organization (FAO).
The collection includes over 36,000 entries, of which 26,500 are cultivated Phaseolus
vulgaris, About 1,300 are wild types of common beans, and the rest distant relatives
of the common bean. Safeguarding, studying, and sharing this germplasm are fundamental
responsibilities implied by CIAT's global mandate for bean research within the
Consultative Group on International Agricultural Research (CGIAR).
Because the huge number of accessions greatly complicates detailed evaluation of the
germplasm for useful traits, CIAT scientists have created more manageable core
collections. These are small but thoroughly representative subsets of the gene bank’s
entire Phaseolus holdings. The core collection of domesticated common bean
contains about 1,400 accessions, while the collection of wild common bean consists of
about 100 accessions.
In recent years bean researchers at CIAT and in national programs of Latin America and
sub-Saharan Africa have been evaluating the core collection for a wide range of traits,
such as insect and disease resistance and tolerance to low phosphorous. Useful materials
have been identified and incorporated into breeding programs at CIAT and elsewhere.
Crop Improvement
Bean improvement research at CIAT concentrates on two main tasks: 1) developing
germplasm that offers farmers distinct advantages with or without purchased inputs and 2)
designing strategies for managing diseases and pests in bean-based cropping systems.
In this first line of research, a key activity involves the identification and
development of germplasm that is tolerant to drought and low soil fertility. In
conjunction with this work, we seek to identify the plant features or mechanisms that
account for traits such as efficient use of phosphorus in beans. These insights better
enable breeders at CIAT and elsewhere to select for stress tolerance and combine it with
other desirable traits, such as higher yield and preferred grain types. Tolerance to
physical stresses must also be combined with multiple resistance to diseases as well as
with resistance to major pests. Toward this end our bean scientists continually screen and
select the germplasm for disease and insect resistance and then "pyramid"
resistance genes in agronomically desirable materials. These experimental materials are
distributed to national programs for local evaluation through a series of germplasm
nurseries.
Our research on disease and pest management in bean aims to speed the development of
component technologies, principally disease and pest resistant germplasm but also
biological and cultural controls. This work involves ongoing efforts to characterize and
monitor major diseases and pests. Better understanding pathogen and pest diversity and
severity across environments is vital for combating these stresses. We also characterize
genes for disease and pest resistance, with a view to combining them more effectively
through bean improvement.
While focusing mainly on dry beans, CIAT scientists are also working to improve snap
beans. Demand for fresh snap beans for domestic consumption or export is growing in
Africa, Asia, and Latin America, and sales are an excellent source of cash income for
small farmers. Much of the Center's strategic research on dry beans, especially that
dealing with diseases and pests, is readily applicable to snap beans.
Biotechnology
Classical breeding within the primary gene pool of common bean has given excellent
results in the last two decades, with tangible benefits for farmers. To speed progress in
this work and to harness valuable genes from wild Phaseolus and species distantly
related to beans, we began in the late 1980s to integrate various biotechnology techniques
into problem-solving research on the crop. Here are two recent highlights of that work:
- In studies that apply molecular marker techniques to the common bean core collection,
CIAT scientists have achieved a better understanding of the genetic makeup and diversity
of the crop. Similar studies are being carried out with a core collection of wild Phaseolus.
This research is essential for using the available genetic resources more effectively in
crop improvement.
- Through improved embyro rescue methods and a backcrossing strategy, CIAT scientists have
succeeded in hybridizing common bean with the distantly related species P. acutifolius,
or tepary bean, which possesses genes for resistance to common bacterial blight (CBB),
leafhoppers, and drought. The resulting breeding lines have shown high levels of
resistance to CBB. They have been distributed to national bean programs for evaluation of
other traits, including tolerance to drought, and low soil fertility and resistance to
leafhopper.
- CIAT researchers have developed a molecular marker-assisted approach to improving beans
for resistance to bean golden mosaic virus (BGMV) that has cut breeding time and effort by
about 60 percent. BGMV is a major production constraint of the crop in Central America and
Mexico. One major source of BGMV resistance is the recessive gene known as bgm-1, which
comes from a Mexican landrace. In 1996 the US Department of Agriculture (USDA) identified a molecular marker
associated with the gene—in this instance a RAPD. CIAT scientists then converted this
to a more useful type of marker called a SCAR. These have the advantage of highly stable
expression and are thus more efficient than RAPDs in marker-assisted plant breeding. The
results of recent molecular marking and selection work are highly encouraging,
demonstrating not only the effectiveness of the SCAR-based strategy for selecting
BGMV-resistant beans but also its efficiency.
From the earliest days of CIAT, bean researchers debated the best way to transfer the
results of their research to the poor small farm family. In 1978 the center pioneered the
development of a regional bean research network for Central America and the Caribbean,
known as PROFRIJOL. A similar network,
PROFRIZA, was established for the Andean zone in 1988. Both Latin American networks have
been supported by the Swiss Agency for Development and Cooperation (SDC).
Based on this model, the Center helped establish other networks in sub-Saharan
Africa’s eastern, central, and southern regions in the mid-1980s. Currently, two
networks—the Eastern and Central Africa Bean Research Network (ECABRN) and the
Southern Africa Bean Research Network (SABRN)—operate within the framework of the
Pan-African Bean Research Alliance (PABRA). Network activities in Africa are financed
principally by the Canadian International Development Agency (CIDA), SDC, and the US Agency
for International Development (USAID).
The networks are also backed by two key subregional organizations, the Association for
Strengthening Agricultural Research in East and Central Africa (ASARECA) and the Southern Africa Centre
for Cooperation in Agricultural Research and Training (SACCAR).
The bean networks are voluntary associations of national research institutions as well
as universities and NGOs. Their purpose is to strengthen local problem-solving capacity
and speed the development and transfer of improved technology through regional
cooperation. CIAT contributes improved germplasm, training, and technical assistance.
Through democratic governance the networks set regional priorities, make resources
available for research, manage adaptive research projects, and share results.
While feeding into the regional networks, bean research at CIAT also draws heavily on
partnerships with universities in developing countries (such as the Escuela Agricola
Panamericana in Honduras) as well as in industrialized countries (e.g., Cornell University and the Universities of California and Wisconsin in the USA and the University of Ghent in Belgium). These
ties are especially valuable in our efforts to integrate biotechnology techniques into
problem-solving research.
Since CIAT's establishment in 1967, national agricultural research programs in 39
countries have released 362 bean varieties—including 238 in Latin America and 111 in
Africa—based on germplasm provided by the Center. These varieties are planted on a
total area of nearly 2.4 million hectares and have generated cumulative benefits of almost
$1.3 billion in 1990 US dollars. In Latin America Brazil and Guatemala have captured a
particularly large share of these benefits, while in Africa Rwanda has been the single
largest beneficiary of bean improvement at CIAT.
The multiple disease resistance of new bean varieties has helped farm families by
reducing crop losses and lowering production costs. Higher productivity has benefited
consumers by permitting a steadier supply of beans at lower, more stable prices. Improved
varieties have had environmental impacts as well. By decreasing the need for pesticides,
the new beans have helped diminish contamination of water and soil. And by permitting more
intensive production on land already in production, they have reduced pressure on fragile
environments, such as hillsides and forest margins. In the sections that follow, we
present some highlights of germplasm impact.
Latin America
Over the last decade or so, total bean production in Latin America has risen 25
percent—to 5.3 million tons in 1993-95 from 4.2 million tons in 1983-85. At the same
time, total area has risen by only 2 percent—to 8.1 million hectares from 7.9
million—and the annual rate of growth in area has actually declined to -0.5 percent.
Increased production has thus resulted mainly from higher yields. The annual growth
rate in yield is now at about 2.7 percent (compared to 1.9 percent a decade ago), and this
is well above Latin America's average rate of growth in population (1.9 percent). With
beans more readily available in the marketplace, per capita consumption has started to
rise as well.
In some parts of Latin America, the changes have been more pronounced than in the
region as a whole. For example, in the Andean zone (Bolivia, Colombia, Ecuador, and Peru),
bean production was essentially stagnant until the early 1990s. Rates of growth in yield
and production lagged well behind population growth. But by 1995 bean production in these
countries as a whole had risen sharply, apparently as a result of higher yields.
A growing body of evidence from field studies suggests that improved varieties have
contributed importantly to yield increases. A literature database maintained on CIAT's Web
site contains abstracts of about 40 such studies.
One of the earliest analyses was conducted in Costa Rica. This work cast doubt on the
then conventional view that technical change generally bypasses small farmers in Latin
America. The study documented widespread adoption of new bean varieties, together with a
new and more profitable bean production system.
Central America as a whole has benefited from cooperative development in the 1980s of
bean varieties resistant to Bean Golden Mosaic Virus. This virus had devastated bean crops
throughout the region as well as in Mexico and the Caribbean. Within 4 years after release
of the first resistant lines, they had been widely adopted in Guatemala and neighboring
countries. At present about 40 percent of Central America's total bean area is planted to
varieties of CIAT origin.
In Brazil a series of surveys conducted during the early 1990s by CIAT and several
national organizations found that improved varieties were being planted on 75 percent of
the total bean production area in four states (Espírito Santo, Goias, Minas Gerais, and
Rio de Janeiro). Their economic impact, through additional production, was estimated at
US$85 million annually.
A 1990 survey carried out by CIAT economists in Peru's northern Cajamarca department
documented the success of the variety Gloriabamba, released 3 years earlier by Peruvian
bean researchers. Despite the harsh growing conditions of this remote semiarid region, 65
percent of small farmers were growing the variety on about 35 percent of the total bean
area, with an average yield increase of 27 percent. The additional production made
possible by Gloriabamba was estimated at 3,038 tons per year, worth $1.5 million.
In Bolivia's Eastern Plains, where bean production was not even a part of local
agricultural tradition, the crop was introduced during the early 1980s for production in
the winter season. Previously, a lack of options during that period had forced farmers to
seek temporary work elsewhere. But now many of them stay home to produce beans for export,
mainly to Brazil, Colombia, and Japan. To increase returns from the enterprise, small
farmers belonging to a bean production cooperative added an export arm to their
organization, and it now earns $3 million annually.
Sub-Saharan Africa
Improved bean germplasm is spreading in this region and beginning to have an impact
according to field studies, but the effects are still not evident in national production
figures. In fact, as mentioned previously, growth in the continent's bean output still
lags well behind demand.
It is encouraging, though, that progress has made even under the most trying
circumstances, as in Rwanda. The vast majority of the country's farmers grow common beans,
and the crop accounts for a third of all calories and two-thirds of all protein consumed
by Rwandans. Since the 1980s the national bean program, with CIAT support, has released
about 20 new climbing beans of Mexican origin, which show marked advantages over bush
beans and local climbing varieties, especially in terms of yield and root rot resistance.
They are the ideal technology for a country where producing more food on less land is of
the utmost urgency.
In 1993 a nationwide survey found that 43 percent of all Rwandan farm families were
growing improved climbing beans on about 20 percent of the country’s total bean
growing area. The new beans raised production by 66,000 tons a year, generating extra
income of about US$15 million.
In late 1995 a new survey was conducted to monitor the impact of seed aid following the
genocide and civil war that shattered the country in 1994. Remarkably, the study found
that, despite the violence and its aftermath, improved climbing beans were being grown by
nearly half of the farmers surveyed and accounted for a third of the seed sown.
Since then the climbing bean varieties that appeal to Rwandan farmers have also been
spread by means of the regional networks to Burundi, Congo (formerly Zaire), Ethiopia,
Kenya, Tanzania, Uganda, and Zambia. A 1996 study conducted near Kakamega in western Kenya
showed that 1,000 farmers had adopted one or more of five climbing varieties within four
growing seasons after their introduction. A similar study carried out in central Kenya
during 1998 found that 1,700 farmers were growing these varieties and selling the seed to
neighbors at premium prices.
The impact of new bush bean varieties is evident in northern Tanzania and southeastern
Uganda. The higher yields and disease resistance of the varieties have strengthened the
food security of farm families and enabled them to produce a surplus for the market. For
example, a survey conducted in Uganda's Mbale District showed that two new varieties had
increased bean supplies during periods of food shortage, raised adopting farmers' cash
income, and reduced the amount of labor women invest in gathering wild vegetables to
stretch dwindling food supplies. A popular new variety in northern Tanzania has been shown
to have environmental benefits as well. Because of its shorter cooking time, it reduces
annual consumption of firewood in rural households by 10 percent.
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