VARIABILITY IN INDIVIDUAL NODULE ACTIVITY OF SINGLE STRAINS OF RHIZOBIUM-ETLI AND R-TROPICI IN SYMBIOSIS WITH PHASEOLUS-VULGARIS

A green-house experiment in Leonard jars was conducted to study the va riability of nitrogenase activity (acetylene reduction) of individual nodules of Phaseolus beans inoculated separately with 19 strains of Rh izobium tropici and 6 strains of R. etli. Both species showed a wide r ange of activities with a C.V.=80% for R. tropici and C.V.=70% for R. etli. These data indicate that Rhizobium species with reiterated nif g enes may present similar variability of single nodule activity as Rhiz obium species containing a single copy of nif gene and that the use of either R. tropici or R. etli may be used for inoculant production wit h precaution for loss of effectiveness.