Allelic Variation for a Short‐Specific Polygalacturonase in Turnera subulata: Is It Associated with the Degree of Self‐Compatibility?

We demonstrate the occurrence of allelic variation at the TSPG locus that encodes a polygalacturonase localized to the transmitting tissue of styles of short-styled plants of Turnera spp. Using DNA sequencing, we infer and compare amino acid sequences of two alleles of TSPG and show that they differ by an amino acid substitution in the putative mature polygalacturonase, resulting in different predicted isoelectric points (pI). The predicted pI differences approximate those estimated using isoelectric focusing. An assay of F2 progeny reveals a complete correspondence between allelic variation at the TSPG locus, as detected by a cleaved amplified polymorphism, and the pI profile of the polygalacturonase. We determine whether there is an association between allelic variation at TSPG and the strength of self-incompatibility by generating F2 progeny segregating for the two alleles of TSPG, and we also introduce variation for self-compatibility into the family by ensuring that one of the parental plants is self-compatible.We screen 138 F2 progeny for their degree of selfcompatibility (selfed seed set) and genotype at the TSPG locus. The results of two replicate experiments indicate that the strength of self-compatibility is weakly associated with the TSPG genotype of the F2 progeny, but we cannot conclude that TSPG is necessarily causal.