Interspecific Crosses between Rhizobium leguminosarum and R. meliloti: Formation of Haploid Recombinants and of R-primes

Abstract

SUMMARY: Using R68.45 as a conjugative plasmid in crosses between strains of Rhizobium leguminosarum and R. meliloti, transfer of chromosomal genes occurred. Haploid recombinants were formed in which rif and str alleles were transferred from R. leguminosarum to R. meliloti. In crosses in the reverse direction haploid recombinants arose at barely detectable frequencies and progeny were isolated which were high frequency donors of the selected allele. Genetic evidence showed that such progeny harboured R-primes in which sections of the R. meliloti chromosome were inserted into R68.45. Four different classes of R68.45-prime, each carrying a different prototrophic marker, were obtained.