LOCALIZATION OF T-DNA INSERTIONS IN PETUNIA BY FLUORESCENCE IN-SITU HYBRIDIZATION - PHYSICAL EVIDENCE FOR SUPPRESSION OF RECOMBINATION

Using fluorescence in situ hybridization (FISH) with metaphase prepara tions, we localized a 4-kb single-copy T-DNA sequence in a group of pe tunia transformants, The selected T-DNAs previously had been shown to be linked to the phenotypic marker Fl on chromosome II, Linkage analys is had revealed that recombination around the FI locus is suppressed i n a wide cross relative to an inbred recombination assay, The localiza tion of six FI-linked T-DNAs and the Fl locus itself, using FISH, reve aled a number of aspects of recombination in petunia: (1) the central region of chromosome II showed at least a 10-fold suppression of recom bination in wide crosses relative to the distal region; (2) recombinat ion in wide hybrids over two-thirds of the chromosome was extremely lo w; and (3) recombination between completely homologous chromosomes in an inbred cross also was suppressed in the central region, In addition , the T-DNAs were not evenly distributed along the chromosome, suggest ing a possible preference for a distal position for T-DNA integration, Implications for such a preference are discussed.