TITLE:
Iron Content of Market-Identified and ISABU-Recommended Biofortified Common Bean (Phaseolus vulgaris) Varieties, before and after Cultivation in Ruyigi Province, Burundi: A Comparative Agronomic Evaluation
AUTHORS:
Munezero Belyse, Kisuse Juma, Senkoro Mbazi, Sagam Caleb, Mfinanga Sayoki, Sindayikengera Sévérin, Niyukuri Jonathan
KEYWORDS:
Biofortification, Iron Content, Common Bean, Phaseolus vulgaris, Soil Iron, Burundi, Child Nutrition
JOURNAL NAME:
Food and Nutrition Sciences,
Vol.17 No.11,
November
6,
2026
ABSTRACT: Background: Iron deficiency is a leading cause of childhood anemia worldwide and in Burundi. Biofortifying staple crops such as common beans (Phaseolus vulgaris) can increase daily iron intake. Butezi District, which has one of the highest rates of chronic malnutrition in Ruyigi Province, where childhood anemia affects 71%, illustrates this issue. Iron levels in a bean variety at harvest depend on genetic traits, farming practices, and soil conditions, highlighting the need to understand how soil-related factors influence iron content. Objective: This research aimed to evaluate the iron content of four locally identified biofortified bean varieties available in the market and compare them with four official ISABU varieties suited to the cultivation and climate of the Butezi health district. We compared them before and after cultivation under consistent field conditions within the study area. Methods: We collected and analyzed soil samples before planting. At ISABU, laboratory tests on seeds from eight varieties determined initial iron levels. We grew four of these varieties (the ISABU-recommended group) at four experimental hills, with one plot per variety at each hill, and reevaluated them after harvest. We selected the four market-identified varieties through a prior community survey in which households named the iron-biofortified varieties they recognized, followed by visits to the markets most commonly used to purchase these varieties for laboratory analysis. Because we could not independently verify biofortified status for these seed lots, we describe them throughout as market-identified rather than confirmed biofortified varieties. We then compared iron content within each variety before and after cultivation, and between the two groups. Results: The four ISABU-recommended varieties in the study area had an average iron content of 115.0 mg/kg, more than twice the 53.1 mg/kg found in the four market-identified biofortified varieties. After one cultivation cycle across four soil types in Butezi, iron content decreased in 15 of 16 variety-by-soil combinations, with a mean decrease of 51.3% across these combinations (ranging from −83.7% to +57.1%); computed directly from the overall group means, the decrease was 57.9% (from 115.0 to 48.4 mg/kg). The final average was 48.4 mg/kg, below the initial levels of the market-identified varieties. Iron retention was highest in clayey soil (average: 60.3 mg/kg), while stony soil showed the lowest (37.0 mg/kg), despite having the highest total iron and phosphorus contents. Only the Kaneza variety showed an increase in iron content, specifically in clayey soil (+57.1%). Changes in zinc, calcium, and protein levels after cultivation were minimal. Conclusion: The anticipated genetic iron benefits of ISABU biofortified beans were inconsistent under current farming conditions in Butezi. Instead, soil type, particularly the contrast between clayey soils and phosphorus-rich stony soils, was more strongly associated with the extent to which these benefits were expressed at harvest than variety choice. Because each hill represented a single soil type, this association cannot be statistically separated from other hill-specific conditions. These results suggest that promoting iron-biofortified beans in Ruyigi should be informed by further, better-replicated soil-specific trials to confirm whether genetic traits can be realized more consistently. The observed benefit on clayey soil in Kaneza is based on a single measurement and should be considered preliminary (pilot) data, requiring further validation through additional trials.