Competition studies with Rhizobium trifolii in a field experiment

Abstract

McLoughlin, T.J. Bordeleau L.M. & Dunican, L.K. 1984. Competition studies with Rhizobium trifolii in a field experiment. Journal of Applied Bacteriology56, 131–135.Competition studies were carried out in a field experiment by comparing the ability of antibiotic marked Rhizobium strains inoculated at three inoculum levels in forming nodules against an effective indigenous Rhizobium population of 1.5 times 105/g. Three inoculum strains were assessed. It was seen that by increasing the level of inoculum there was a corresponding increase in the number of nodules formed by the introduced strains. G1067 formed a high proportion (85%) at the highest level, whereas the other two inoculum strains occupied less than 50% of the nodules at the same level. Persistence of the inoculum strain was measured into the second season; G1032 could not be detected, G1006 (another ‘foreign’ strain) formed 43% and G1067 formed 97% of the nodules sampled. The indigenous Rhizobium population isolated from nodules was shown to be heterogenous, and 15 different intrinsic antibiotic resistance patterns were found. Fifty per cent of the isolates fell in the same group which showed a similar pattern to that of the inoculum strain G1067.