Comparison of homologous recombination frequencies in somatic cells of petunia and tobacco suggest two distinct recombination pathways

Summary Homologous recombination in plants was studied using an extrachromosomal recombination assay in which intermolecular homologous recombination between two complementary plasmids restored a selectable marker gene. Several vectors containing an insertion into or deletions within the coding region of the neomycin phosphotransferase (NPT‐II) gene were designed. Plasmids were introduced, in pairwise combinations, into protoplasts and homologous recombination events were measured by counting the number of NPT‐ll‐resistant colonies. A 10‐fold increase in recombination frequency was observed in Petunia hybrids RL01 compared to Nicotiana tabacum SRI. This difference occurred when one or both of the co‐transferred recombination plasmids was offered in a circular form. Apart from such specific differences between two cultivars from different species, a two‐to fivefold increase in recombination frequencies was observed when the genomic TBS (transformation booster sequence) fragment from P. hybrids was added onto one of the transferred plasmids. TBS‐specific stimulation of recombination was observed in Petunia RL01. These data suggest that two different recombination pathways may be present in plants.