Drought affects 60% of the bean-producing regions, and is responsible for total crop failure in the worst-case scenario. But this fight is not lost as demonstrated by 13 new bean genotypes developed by scientists of CIAT’s Bean Program using interspecific crosses. The work was done in close collaboration with the Autonomous University of Barcelona (UAB), with the support of the Bill & Melinda Gates Foundation (BMGF) and CGIAR Research Program on Grain Legumes.
This output resulted from several years of work aimed at achieving a better understanding of the physiological basis of improved drought resistance in common bean. A major lesson learned from this work is that no single morpho-physiological trait stands out for its unique and dominant contribution to drought resistance in common beans.
Even though it sounds like banking jargon, after evaluating 36 advanced lines over two seasons, scientists of CIAT’s bean breeding program succeeded in classifying the genotypes into two groups: water savers and water spenders. The grouping is based on their morpho-physiological responses to drought stress in terms of water use and other key traits such as carbon isotope discrimination, rooting depth, and photosynthate remobilization.
The water saving genotypes are characterized by their ability to reduce stomatal opening and transpiration with smaller leaf size. But are efficient in remobilizing carbon from vegetative structures to grain production. These genotypes could be more suitable to bean farmers in semiarid to dry environments, dominated by terminal type of drought stress in Central America, Africa, northern Mexico and north-east Brazil. This group of genotypes include SER 16, ALB 60, ALB 6, BFS 10, and BFS 29, which are small red beans. In fact, SER 16 is a drought-resistant variety developed by CIAT and released in Rwanda, which soon will be released in Nicaragua as well.
The water spending genotypes are characterized by their deep rooting ability, which maximizes their water extraction capacity to facilitate crop growth, pod development and grain filling under drought stress conditions. They are suitable for cultivation in areas exposed to intermittent drought in Central America, South America, and Africa, particularly in regions where rainfall is intermittent during the season and soils have good water storage capacity. This group of genotypes include NCB 280, NCB 226, SEN 56, SCR 2, SCR 16, SMC 141, RCB 593, and BFS 67. An untrained consumer may identify these as small black or small red beans.
But that is not it. Those 13 bean lines improved by CIAT – remarkably drought resistant – showed a grain yield that doubles the yield under drought stress of three leading commercial cultivars in Latin America: DOR 390, Perola, and Tío Canela.
The success in responding to the challenge posed by drought – main abiotic limiting factor for bean production – seems to be largely due to a strategic combination of morpho-physiological traits from contrasting sources of bean germplasm. These new genotypes not only minimize crop failure in smallholder systems but also contribute to yield stability and resilience to confront drought stress.
This article was originally published in CIAT Blog on 29 September 2015