Nitrogen fixation efficiency of rhizobia nodulating Apios americana.

ABSTRACT

In this study, the efficiency of Apios rhizobial isolates in N2 fixation was compared with a typical Bradyrhizobium strain [USDA 3451] in a greenhouse pot experiment. The study exhibited marked differences among Apios isolates in a nodule number and nodule mass top dry weight and total uptake of nitrogen by-plant. There were approximately two-fold differences in nitrogen accumulated within the plant between the most and the least effective isolate. The study also revealed that all isolates of Apios rhizobia [B. Sp.] gave a significant growth response despite the presence of indigenous B. Sp. [Vigna]. The differentiation between Apios isolates in their efficiency to fix atmospheric N was assessed using acetylene reduction technique for measuring N-ase activity. Data also showed that there were significant differences in the amount of N fixed between the different isolates of Apios