Unveiling contrasting iron efficiency strategies in common bean (Phaseolus vulgaris L.) genotypes under iron deficiency.

Abstract

Iron (Fe) deficiency in food crops, particularly on calcareous soils, limits productivity and human nutrition. This study investigated two common bean (Phaseolus vulgaris) genotypes, Guaymí (high Fe-accumulating, HI) and Matambú (low Fe-accumulating, LI) to understand physiological and genetic mechanisms underlying Fe uptake, shoot accumulation, and adaptation under low and adequate Fe conditions. Plants were grown under controlled Fe-deficient and Fe-sufficient conditions. Root-induced acidification, ferric reductase activity, leaf chlorosis, and Fe and Mn accumulation were measured. Gene expression of Fe-related transporters and mobilisation pathways was assessed at early and prolonged stages of deficiency. Under Fe deficiency, HI showed stronger root acidification, higher ferric reductase activity, and greater Fe uptake compared with LI. HI maintained growth, leaf Fe, and Mn content, whereas LI relied on polyphenol-based Fe mobilisation. Early-stage Fe-related gene expression differed between the two genotypes but converged under prolonged deficiency. The HI genotype demonstrates superior Fe absorption efficiency and adaptive responses under Fe-limited conditions, sustaining growth and Fe accumulation in roots and shoots. These findings highlight the potential of selecting or engineering Fe-efficient cultivars to improve crop productivity and nutritional quality, offering a promising strategy to address Fe deficiency in agriculture and human diets.