Potential of Common Bean to Enhance Dietary Iron Availability in Humans: Germplasm Diversity and QTL Analysis.

We are interested in the improvement of iron nutritional status of humans living in developing world countries where iron deficiency anemia is quite severe.  We also wish to promote the use of plant-based food sources to improve human iron status, and thus are focusing on staple food crops like common bean (Phaseolus vulgaris).  We are using an in vitro cell culture method (Caco-2 cells), along with a diverse set of germplasm, to measure iron bioavailability and to identify factors within the beans that contribute to dietary iron absorption.  We studied 248 bean entries that were grown in Washington State in 2010.  Ground seed samples were mixed with water (1 part bean powder to 4 parts water) and cooked for 30 minutes at 121 C in a steam sterilizer.  Once cool, they were transferred to a -20 C freezer for at least 24 hrs.  The samples were then lyophilized for 72 hrs.  Once out of the freeze dryer, they were ground in a mortar and pestle and stored at 4 C until the iron bioavailability experiments.  This involved mixing aliquots of cooked bean sample with a known quantity of iron, digesting this using an in vitro digestion (a mix of digestive enzymes), then feeding this ‘food’ to the Caco-2 cells.  Ferritin formation in the cells (after 24 h) was used as a proxy for iron bioavailability potential; a control sample of ground and cooked chickpea was run with each set of cells and was used to normalize the data in each assay.  Our results (248 entries; average of 5 replicates per entry) indicate that the normalized Fe bioavailability values demonstrated a 2.7-fold range.  We are currently using an association mapping strategy with these lines to identify QTLs for enhanced iron bioavailability potential.  Results of these analyses will be presented.  This work is part of the Bean Cooperative Agricultural Project (Bean CAP), funded by USDA-NIFA.