S allele discrimination in styles of Petunia hybrida bearing stylar-conditioned pseudo-self-compatibility.

A cross between a 0% pseudo-self-compatible (PSC) plant (S3.3) and a 100% PSC plant (S1.1) yielded an F1 population which, when selfed, produced a high mean seed set which was not significantly different than that produced when the F1 was backcross pollinated by the 100% PSC parent. Backcross pollinating the F1 with the 0% PSC parent yielded no seed. No S3.3 plants were recovered in the F2 populations, indicating that pollen tubes containing the S3 allele were inhibited during pollen tube growth of the selfed F1 plants. Apparently stylar-conditioned PSC does not remove all discriminatory power from these petunia styles. Crossing the F1 (S1.3) with an self-incompatible (SI) plant (S2.2) produced plants which were used for computation of a standard linkage test. An approximate map distance of 28 units was found between the S specificity locus and the major gene(s) which influenced its expression. Other generalized PSC modifying genes apparantly were not linked with the S locus.