Segregation distortion of T-DNA markers linked to the self-incompatibility(S) locus in Petunia hybrida

In plants with a gametophytic self-incompatibility system the specificity o f die pollen is determined by the haploid genotype at the self-incompatibil ity (S) locus; In certain crosses this can lead to the exclusion of half th e gametes from the male parent carrying a particular S-allele. This leads t o pronounced segregation distortion for any genetic markers that are linked to the S-locus. We have used this approach to identify T-DNA insertions ca rrying a maize transposable element that are linked to the S-locus of Petun ia hybrida. A total of 83 T-DNA insertions were tested for segregation dist ortion of the selectable marker used during transformation with Agrobacteri um. Segregation distortion was observed for 12 T-DNA insertions and at leas t 8 of these were shown to be in the same linkage group by intercrossing. T his indicates tl-lat differential transmission of a single locus (S) is pro bably responsible for all of these examples of T-DNA segregation distortion . The identification of selectable markers in coupling with a functional S- allele will allow the preselection of recombination events around the S-loc us in petunia. Our approach provides a general method for identifying trans genes that are linked to gametophytic self-incompatibility loci and provide s an opportunity for transposon tagging of the petunia S-locus.