STATISTICAL DIFFERENTIATION BETWEEN SELF-INCOMPATIBILITY AND PSEUDO-SELF COMPATIBILITY IN PETUNIA-HYBRIDA HORT USING FEMALE AND MALE COEFFICIENT OF CROSSABILITY

Discriminating styles (DS), pollen-mediated pseudo-self compatibility (PMPSC), and general pseudo-self compatibility (PSC) phenomena were in vestigated by re-analyzing data from Petunia hybrida where known S gen otypes were used. This demonstrated how female coefficient of crossabi lity (FCC)/male coefficient of crossability (MCC) scatter diagrams and regression analyses aid in identifying and quantifying PSC within an self incompatible (SI) population. One of the female testers was ident ified by statistics to be SI, not DS, in contrast to what was reported in the original report, where all the plants were assumed to have ope rating DS. In addition, none of the females expressed PMPSC. Based on regression analysis and chi-square tests, a threshold between 27% and 31% PSC was estimated to be necessary for expression of DS. The presen ce of DS was also required to test for the existence of PMPSC as repor ted previously. The upper left-hand quadrant of the FCC/MCC scatter di agram which contains all the deviants from the theoretical SI model, i s the location expression of DS has been identified. Placement for PMP SC deviants is not possible, due to the interrelationship with DS. Per cent PSC did not directly equate with the different types of PSC pheno mena but was useful for identifying and ranking DS in female parents. The compatible tester used in this experiment did not always produce t he highest outcross seed set with the females as expected. Therefore, due to the confounding effects of the different types of PSC, it is im portant to choose the compatible testers with care. Regression analyse s of FCC/MCC values indicated that S2.2 and S1.2 male testers did not behave in a similar fashion to S1.1 testers. It is hypothesized that t his disparity could be the result of the expression of a general PSC g ene, different from the DS or PMPSC genes, which is linked to the S2 a llele. Since these general PSC effects associated with the S2 allele a re minor in comparison to DS and PMPSC, it was necessary to distinguis h the difference using statistical analysis.