Slender green beans air-freighted from Kenya to markets in Western Europe are a profitable crop for high-altitude farms across sub-Saharan Africa. Breeding efforts at Cornell could help their lower altitude neighbors also harness the crop’s economic potential.
Green beans are Kenya’s most important horticultural export, earning farmers five to 10 times more than the dry beans they traditionally grow. However, there are two significant barriers to the expansion of this lucrative market: the varieties available are sensitive to high temperatures during flowering and susceptible to the common bean rust fungus.
"Green beans are typically grown at altitudes higher than about 5,000 feet, which can have a temperate climate despite their proximity to the equator, but competition and land prices at these higher altitudes has increased," said Phillip Griffiths, vegetable breeder and associate professor of horticulture.
"To consider sub-Saharan Africa a region only for subsistence farming is to overlook opportunities for small-holder growers to produce crops with much higher values," he added. "The ability to expand green bean production into marginal areas at lower altitudes would provide new opportunities for farmers, but it requires the development of new varieties that combine heat tolerance with multiple rust resistance genes."
Because these two traits are also important for U.S. growers, Griffiths and his colleagues Tim Porch, Ph.D. ’01, and Talo Pastor-Corrales of the USDA Agricultural Research Service, already had sources for both in hand, ready for breeding into the specific types of slender green beans needed for eastern Africa.
The funding for the breeding came from several sources, including the Alliance for a Green Revolution in Africa, the Toward Sustainability Foundation, Cornell’s Mario Einaudi Center for International Studies and the Cornell Assistantship for Horticulture in Africa (CAHA), a recently established doctoral scholarship established by an anonymous donor.
Kenyan Charles Wasonga, Ph.D. ’10, the first recipient of the CAHA fellowship, took the field trials of the new green beans through two years at six sites, including partner institutes in Kenya and Tanzania. He identified promising types with comparable yields at lower altitudes (about 3,600 feet) and a combination of rust resistance genes that protected against all known rust strains in the region.