Linkage Mapping in Rhizobium leguminosarum by means of R Plasmid-mediated Recombination

Wild-type R plasmids of the P1 incompatibility group mediated the transfer of chromosomal genes in Rhizobium leguminosarum, but only at very low frequencies. Two P1 R plasmids, which had originally been selected in Pseudomonas aeruginosa for enhanced donor properties, promoted much higher levels of gene transfer in R. leguminosarum. One of these, R68.45, was used for linkage mapping. All markers tested mapped on a single circular linkage group. Segments of donor chromosome up to at least one-seventh of its total length were transferred and integrated into the recipient chromosome.