IRON BIOFORTIFICATION IN COMMON BEAN (Phaseolus vulgaris L.)

Iron deficiency anaemia is the most prevalent micronutrient deficiency affecting more than 2 billion people throughout of the world. Iron bioavailability may be strongly reduced by the presence in the seeds of iron absorption inhibitors, such as phytic acid (IP6) and polyphenols (PP). In different crop species low PP genotypes can be easily identified, conversely natural variability in IP6 content is not very high and the best way to gain significant IP6 reduction is by obtaining low phytic acid (lpa) mutants. Although such types of mutants have been identified in several grain crops, often IP6 reduction is associated with negative agronomic traits, such as lower seed viability and emergence, reduced plant growth rate and grain yield. These findings may limit the use of lpa mutants for iron biofortification, since acceptable agronomic performance should be guaranteed to small farmers and poor populations that would benefit from biofortified crops. Due to its worldwide consumption and nutritional qualities, common bean (Phaseolus vulgaris L.) has been identified as a strategic target crop for iron biofortification. We have isolated a bean lpa mutant having a 90% seed IP6 reduction and showed it is defective in a MRP type ATP-binding cassette transporter (Pvmrp1) specific for IP6. Agronomic analyses of the original lpa mutant and of derived lpa lines have shown that seedling emergence, seed yield and plant growth were not affected. In vitro and in vivo analyses confirmed significant increases of iron bioavailability in bean lpa seeds. To gain more understanding on the increased iron bioavailablity observed in the lpa mutant we decided to study possible changes in spatial distribution of mineral nutrients. For this purpose we used by ?-XRF imaging for the localization of Fe and P, and Fe-K-?-XANES for Fe speciation and ligand environment in specific seed tissues of common bean lpa and wild type genotypes. The same analysis was performed on different genetic backgrounds with contrasting polyphenol concentrations. Results will contribute to elucidate the role of IP6 in the subcellular compartmentalization of P and Fe as well as Mn, K, Ca and Mg and consequently indicate the function of PvMRP1 protein. This work was partially supported by: i) Programme FILAGRO "Strategie innovative e sostenibili per la filiera agroalimentare", as part of the activities defined within the Accordo Quadro Consiglio Nazionale delle Ricerche and Regione Lombardia and 2) BeamTime allocation (LS2374) to V-MK and CE by the European Synchroton Research Facility, ESRF, Grenoble, France.