SURVIVAL OF INOCULATED RHIZOSPHERE BACTER IA AND THEIR INFLUENCE ON NATIVE BACTERIAL-POPULATIONS IN THE RHIZOSPHERE OF ALFALFA

The survival of inoculated bacteria and their influence on native bact erial populations in the rhizosphere of alfalfa were investigated in a greenhouse experiment. The plant growth promoting strains Rhizobium m eliloti me18 and Pseudomonas fluorescens PsIA12 were reisolated from t he rhizosphere about 7 weeks after single and mixed strain inoculation . They did not induce lasting changes in the diversity of the native b acterial communities of the rhizosphere. Only within the first week af ter inoculation was an increase in total bacterial abundance observed. In general, the diversity of bacterial communities increased with pla nt age and with proximity to the root tip.