Breeding second‐generation biofortified bean varieties for Africa

Abstract

Micronutrient malnutrition is one of the most serious health challenges facing vastsectors of Africa's population, particularly resource‐poor women and children.Development and utilization of drought‐tolerant, biofortified varieties is probablythe most effective, sustainable, and potentially long‐lasting strategy for reducing mi-cronutrient deficiencies and coping with frequent droughts. Our objective was todevelop second‐generation biofortified bean (Phaseolus vulgaris L.) varieties com-bining drought tolerance, multiple disease resistance, and higher concentrations ofiron and zinc in grain than the first‐generation varieties currently grown by farmersin east, central, and west Africa. Forty‐seven F 2 populations segregating for mineraldensity, resistance to biotic and abiotic stress factors, marketable grain types, andyield potential were developed at Kabete Field Station, and advanced to F4 as popu-lation bulks. During the 2010 long rain season, 6,612 F4 single plants were selectedand used to establish F4.5 progeny rows during the 2011 short rain season at Kabete.These progenies were evaluated for resistance to angular leaf spot, anthracnose, rootrots, and agronomic traits. In 2012, 102 F 4.6 lines were evaluated under drought stressand no‐stress conditions at Kabete and Thika. During the 2012 short rain season, se-lected disease and drought‐tolerant F4.7 lines were evaluated for mineral density andfor their agronomic potential at four locations representing major bean productionenvironments. Results showed significant (p < 0.01) variation for mineral density,drought tolerance, disease resistance, growth habit, grain type, and maturity amongthe populations and their progenies. Iron concentration varied from 30 to 130 ppm.Zinc concentration varied from 10 to 60 ppm. Superior lines were selected fromBF01, BF07, BF16, and BF36 populations. Eighty‐four lines had 50% more yieldunder stress and no‐stress conditions compared with the parental lines, suggestingtransgressive segregation. Results indicate that varieties combining high micronutri-ent density, resistance to diseases and drought, and marketable grain types can bedeveloped from these populations.