The molecular genetics of self-incompatibility in Petunia hybrida
2000
Robbins, T.P. | Harbord, R.M. | Sonneveld, T. | Clarke, K.
The cultivated petunia (Petunia hybrida) has been a popular system in which to study genetic, physiological and biochemical aspects of gametophytic self-incompatibility. As with other members of the Solanaceae a number of S-RNase genes have been isolated for functional S-alleles. We have identified S-RNase sequences for two additional functional S-alleles, Sv and S3. These alleles are more similar to alleles from other families of the Solanaceae (Nicotiana and Solanum) than to any petunia alleles reported previously. The total number of S-alleles in P. hybrida is at least ten in spite of its cultivated origin. However, most cultivars of P. hybrida are in fact self-compatible and this appears to arise from the prominence of a single previously described allele So. The implications of this observation for the origin of self-compatibility in P. hybrida are discussed. The S-locus of P. hybrida has recently been mapped using an indirect method involving T-DNA insertions. Seven T-DNA insertions that were previously shown to be closely linked to the S-locus were physically mapped on the long arm of chromosome III using fluorescent in-situ hybridization. The most tightly linked T-DNA insertions are in a sub-centromeric position. This is consistent with the centric fragments of P. inflata obtained by irradiation mutagenesis that carry additional S-loci and confer a pollen-part mutant phenotype. An S-linked restriction fragment length polymorphism (RFLP) marker. CP100 was used to confirm this chromosomal assignment and has provided evidence for S-locus synteny in the Solanaceae.
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