NITROGEN-FIXATION IN BREEDING LINES OF PHASEOLUS-VULGARIS L

Nitrogen fixation in nine common bean (Phaseolus vulgaris L.) lines wa s estimated using the N-15 isotope dilution method at two locations in two seasons. In the first season at one location no N2 fixation was d etected while in the second season up to 51 kg N ha-1 were estimated. There were significant differences between lines and correlations betw een trials were significant for the amounts of N2 fixed, but not for t otal shoot nitrogen. The plants that fixed the most nitrogen nodulated rapidly after germination. Differences in maximum nodule mass, but no t specific nodule activity, were detected also.