SUPPRESSION OF RECOMBINATION IN WIDE HYBRIDS OF PETUNIA-HYBRIDA AS REVEALED BY GENETIC-MAPPING OF MARKER TRANSGENES

In the course of a heterologous transposon tagging experiment in Petun ia hybrida (n=7), 135 independent T-DNA loci were tested for linkage t o the target genes Hf1 and Fl, which are located on the two largest ch romosomes . Approximately one-third (47) of these T-DNA loci were link ed to one of these two markers. Of these 47 linked-loci, 19 mapped wit hin 1 cM of its marker, indicating a highly non-random genetic distrib ution of introduced loci. However, rather than non-random integration within both of the marked chromosomes, this probably reflects a suppre ssion of recombination around these marker loci in the particular wide hybrids used for mapping. This hypothesis was tested by measuring rec ombination between linked T-DNAs in an inbred background. Inbred recom bination levels were found to be at least 3-fold higher around the Hf1 locus and 12-fold higher around Fl compared to the wide hybrids. Thes e findings may reflect the origin of P. hybrida by hybridization of wi ld species, and while relevant to genetic mapping in petunia in partic ular they may also have more general significance for any mapping stra tegies involving the use of wide hybrids in other species.