Spirited efforts by US and Kenyan scientist has birthed new varieties of green beans that thrive at lower altitudes and are resistant to rust even as it emerges that green beans are one of Kenya’s best earning crops, but hasn’t performed well due to the susceptibility of the crop to rust fungus and limited land for production.

Slender green beans earn farmers five to 10 times more than the dry beans they traditionally grow. However, they are sensitive to high temperatures during flowering and to bean rust fungus. This has meant they do well at altitudes higher than 5,000 feet, where the climate is temperate despite the proximity to the equator.

However, competition has pushed up land prices at these higher altitudes meaning the majority of the farmers can no longer access the right land to grow the crop: a factor that pushed scientists to develop a bean that could be grown in the conditions that prevail for the majority of the region’s farmers.

"The ability to expand green bean production into marginal areas at lower altitudes provides new opportunities for farmers, but it requires the development of new varieties that combine heat tolerance with multiple rust resistance genes," said Phillip Griffiths, a vegetable breeder and associate professor of horticulture at Cornell University during the launch of the new bean.

With the twin traits of heat tolerance and disease resistance equally important to US bean growers, the researchers carried out the initial tests and breeding of the slender green beans in greenhouses in America. The trials of the newly bred beans were later trialed in six different sites in the world, including Kenya. Plants were identified that provided good yields at lower altitudes and also those with rust resistance genes that showed immunity to all local strains of rust.

Charles Wasonga who holds a PhD degree in horticulture from Cornell University carried out the field trials of the new variety bean in Kenya and Tanzania for two years and 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.

The funding for the breeding came from several sources, among them 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.

“This is a major breakthrough for our farmers and for our efforts as research institutions to ensure that farmers get high yielding, disease resistant crops. We have also been involved in our own ventures of developing higher quality bean varieties since traditional beans haven’t been returning good results which explains why everyone is neglecting them,” says Dr Zachary Mwendwa from KARI.

Already KARI has developed a new drought-tolerant bean varieties with higher yields and greater nutrition, which is targeted at Kenya’s canning industry that had relied on the foreign Mexican 142 variety since 1960. The improved varieties were established to improve food security, nutrition, and raising farmers’ incomes through greater commercialisationof a crop fit to counter the climate change challenges afflicting East Africa.

The varieties guarantee yields more than 50 per cent higher than conventional varieties and are the first beans developed specifically for Kenya’s canning industry. They also have more zinc and iron in them, over-riding the need for consumers to buy food supplements when they need more of these minerals. “We want to have as many varieties of beans as possible for our farmers, which do well in various climatic and soil conditions so that we can give them an array of options on what to plant,” says Dr Mwendwa.