In previous years we have reported on the development of drought tolerance in small seeded Mesoamerican beans with a focus on Central America but with implications for Africa as well.

Collaborative research with the Nicaraguan national program is carried out under a project funded by the German government. The national bean program is moving aggressively to test drought tolerant materials in several regions of the country.

Broader deployment of drought tolerance requires combining tolerance with key resistance genes, especially for BGYMV (bean golden yellow mosaic virus) in Central America and recessive resistance to BCMNV (bean common mosaic necrosis virus) for Africa.

This year we report on the recovery of a much larger number of F₅ drought tolerant families producing 50-100% more yield than the checks, from crosses including parents for BGYMV resistance and with acceptable grain color. Several drought tolerant families also carry recessive bc-3 resistance to necrotic BCMNV strains, and this gene permits recovery of the light red color with the highest commercial value. Physiological analysis of Recombinant Inbred Lines (RILs) has advanced, in preparation for gene tagging of important genes for photosynthate transport and grainfilling, and greenhouse screening techniques for rooting depth are very promising. However, field trials in Colombia and in Nicaragua with the Communities and Watersheds project suggest that when low fertility and drought stresses are combined, as often happens on smallholder farms, tolerance to low fertility can be necessary for fuller expression of tolerance to drought.

Contact: Idupulapati Rao and Stephen Beebe