Biofortification of Common Bean for Higher Iron Concentration

Abstract

Common bean (Phaseolus vulgaris L.) is a staple food of smallholder farmers and poor urban consumers in Latin America and eastern-southern Africa among whom iron deficiency is frequent. Bean was domesticated in Mexico and the southern Andes, creating two distinct gene pools. Evaluation of a core collection of 1,441 entries revealed average concentrations of 55 mg kg−1 iron. A breeding target was set at 44 mg kg−1 iron above the level in a local check variety, while 50% of goal or a 22 mg kg−1 advantage was accepted as “biofortified.” In a bioefficacy trial among college-age women in Rwanda, high iron beans improved iron status and enhanced cognitive ability, brain function, and work efficiency. However, breeding progress has been slow, likely due in part to homeostatic mechanisms whereby organisms moderate iron and zinc uptake. This phenomenon may represent resistance to increasing concentration of these elements. Crosses between gene pools may “jumble” genes for homeostasis and permit high levels. A second breeding strategy is the use of sister species that evolved in iron-poor environments and that could be more receptive to iron uptake. Future breeding may also increase attention on improving bioavailability through mechanisms such as non-or-slow darkening grain or low phytate mutants. Changing dietary patterns in developed countries could increase iron deficiency and create demand for iron biofortified beans.

Multivariate genomic analysis and optimal contributions selection predicts high genetic gains in cooking time, iron, zinc, and grain yield in common beans in East Africa

“…There is strong evidence from this and other studies (Raatz et al., 2019) that genetic distance between the two pools is high, but disagreement on the degree of genetic diversity within pools (Bitocchi et al., 2013; Bitocchi et al., 2017; Kwak & Gepts, 2009; Talukder et al., 2010). Narrowing of genetic diversity within the Mesoamerican and Andean gene pools has been documented (Bitocchi et al., 2013), and previous studies also support the use of interpool crossing to increase the potential for future genetic improvement in CKT, Fe, and Zn (Beebe, 2020; Blair, 2013; Blair et al., 2010).…”

Redefining Bean Iron Biofortification: A Review of the Evidence for Moving to a High Fe Bioavailability Approach

“…As stated previously, The target value of 90-94 µg/g was selected based on the premise that the average bean Fe concentration is 50-55 µg/g, and that the 40 µg/g differential of biofortified vs. "normal" was calculated to be necessary to have nutritional benefit, with a fractional Fe bioavailability of the bean estimated at 7% (Mulambu et al, 2017;Beebe, 2020). While sufficient variability has been discovered in bean Fe concentration indicating that high Fe can be a trait to select for, recent studies also indicate a strong environment (E) and genotype by environment (G × E) influence on Fe concentration.…”

“…This approach is based on three major assumptions: (1) the mean bean Fe concentration in target marketplaces is 50-55 µg/g; (2) a higher concentration of Fe in bean varieties correlates to greater Fe absorption when consumed; and (3) a high Fe concentration (target value of 94 µg/g) is a stable trait that can be achieved through traditional breeding methods. These assumptions were established based on analysis of a highly diverse "core collection" of beans established at the Center for Tropical Agriculture (CIAT) in Cali, Colombia in ∼2,000 (Beebe et al, 2000;Islam et al, 2002;Beebe, 2020).…”

Adaptation of Interspecific Mesoamerican Common Bean Lines to Acid Soils and High Temperature in the Amazon Region of Colombia

“…Bean breeding programs have been making progress in identifying the adaptive responses that contribute to an increase in yield under stress conditions [12, [16][17][18][19]. In addition to developing advanced lines capable of adapting to acid soils [9] and high temperatures [11], it is necessary to evaluate new lines for their capacity in increasing efficiency in energy use, leaf cooling and photosynthate partitioning for pod formation and grain filling as well as mineral accumulation in the seed [10,20].…”

“…Andean beans tend to have a higher seed iron concentration than the Mesoamerican beans [2,22] but their level of tolerance to abiotic stress tends to be lower [18]. Improved bean genotypes with higher levels of iron (Fe) and zinc (Zn) have been released in recent years in different regions of the world [20,28]. These new bean varieties are not only biofortified for higher iron and zinc concentration but also perform agronomically as well as standard varieties due to a combination of multiple desirable traits including good yield, color, size and shape of the grain; characteristics that are desired by farmers [20,29].…”