Screening for Nitrogen Fixation and Supply in Faba Bean (Vicia faba L.).

Faba bean is a large biomass legume crop and it can supply most of its N requirement through biological N₂ fixation.  Two goals of the faba breeding program in Saskatchewan are to develop cultivars with high levels of stress tolerant N₂ fixation to support protein in yield, and to supply sustainable N to the next rotation through stover.  Our objectives were to assess 15 genotypes (cultivars and breeding lines) of faba in the field at two locations (SK) in 2009 and 2010 for their ability to take up and to fix N_2, and to develop a screening tool for selecting for superior N acquisition.  We measured amino acids and ureides in leaf, stem, pod and seed partitions (each at flowering, podfill, and close to physiological maturity), final yield, total nitrogen and %Ndfa.  We then calculated amino acid ratios from the tissue concentrations to describe and predict total N content of the crop, fixed N₂, and yield.  In 2011 we tested these relationships in the field against a subset of the genotypes plus additional genotypes not used in equation development.  We will discuss the results of actual versus predictive N assimilation, and which ratios could be effective tools to predict N fixation and stress tolerant N acquisition.