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, because 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. During the
last decade, bean production in Latin America has increased by 25 percent as a result of
higher yields, whereas the area planted has only increased by 2 percent. The annual growth
rate of production, 2.7 percent, now surpasses the population growth rate, with a
resulting increase in consumption per capita. 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, excessive
pesticide use, 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 Diversity
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. The collection includes over 36,000 entries,
of which 26,500 are cultivated Phaseolus vulgaris, About 1300 are wild types of
common beans, and the rest are distant relatives of the common bean.
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 1400 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 phosphoros.
Useful materials have been identified and incorporated into breeding programs at CIAT and
elsewhere.
Geographic Information Systems
The bean core collections were developed with the aid of a geographic
information system (GIS). This helped ensure that the collections are truly representative
of the many diverse environments in which beans evolved and are grown.
Further refinement of this GIS tool has produced a powerful computer
program, called FloraMap, to guide the search for new samples of the genetic diversity of
wild Phaseolus and other species. Based on climate, elevation, soil, and other
features of locations where germplasm has already been collected, FloraMap produces maps
indicating the probability of finding further samples in particular places. In addition to
aiding plant collection, the program is also helpful for planning in situ and ex situ
conservation of wild species.
Crop Improvement
Bean improvement research at CIAT (See Strategy 2000) 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 identifying and
developing 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.
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