DISCRETE DIFFERENCES BETWEEN STRAINS OF DIFFERENT RHIZOBIUM SPP FOR COMPETITIVE NODULE OCCUPANCY ON BEANS

Rhizobium etli strain TAL182 and R. leguminosarum by phaseoli strain 8 002, both of which produce melanin pigment, were tested for their nodu lation competitiveness on beans by paired inoculation with two strains which do not produce melanin: R, tropici strain CIAT899 and Rhizobium sp. strain TAL1145. An assay was developed to distinguish nodules for med by the melanin-producing and non-producing strains. Strain TAL182 had discrete competitive superiority over CIAT899 and TAL1145 for nodu lation of beans. Nodulation competitiveness was not correlated with th e ability to produce melanin pigment or the host range of the Rhizobiu m strains tested.