Genotypic variation in nitrogen fixation by Phaseolus vulgaris L

Field experiments were performed in Austria, Brazil, Chile, Colombia, Guatemala, Mexico, Peru and the United States of America as part of an FAO/IAEA Co-ordinated Research Programme to investigate the nitrogen fixing potential of several cultivars or breeding lines of common bean (Phaseolus vulgaris L.). Each experiment included approximately twenty genotypes of bean, which were compared using the 15N isotope dilution method. Great differences in nitrogen fixation were observed both between and within experiments, with average values of 35% N derived from the atmosphere and highest values of 65 %Ndfa, which is much larger than previously reported for common bean. Such high values for fixation were only observed when environmental factors were favourable. Lines of common bean are therefore available which can support high biological nitrogen fixation. These could be used in breeding programmes to enhance nitrogen fixation in other cultivars. (author). 8 refs, 5 figs, 3 tabs