Symbiotic gene probes hybridize to cryptic plasmids of indigenous Rhizobium meliloti

Abstract

DNA probes for host specific nodulation (hsn) common nodulation (nod), exopolysaccharide (exo), nodule development (ndv) and nitrogenase structural (nif) genes were used to examine a collection of symbiotically effective, genotypically distinct isolates of indigenous Rhizobium meliloti for reiteration of symbiotic DNA sequences on cryptic plasmids. Nineteen of 30 isolates possessed at least one cryptic plasmid with reiterated DNA sequences, and of these isolates 15, 5, and 1 contained cryptic plasmids that hybridized to hsn, nif, and nod gene probes respectively; both hsn and nif probes hybridized to a single cryptic plasmid in each of two isolates. The exo and ndv probes did not hybridize to cryptic plasmids in any of the 30 isolates of R. meliloti.