Biplot approach with self-incompatibility analyses of sib diallel cross data for Lysimachia monelli (Primulaceae)

The biplot is a diagnostic tool used to make a visual appraisal of large data matrices with double entries. It has been most commonly used in crop breeding to evaluate genotype × environment interactions. We have employed the biplot method to study the self- and cross-compatibility reactions as evinced by diallel crosses for full-sib progeny arrays in Lysimachia (Anagallis) monelli, a species that has been shown to have single locus, multiallelic self-incompatibility, homomorphic gametophytic type (GSI). The resultant plots show two and three major groups (inter-compatible, intra-incompatible). In all diallel biplots, the high proportion of the total variation explained by two principal components (PC1 and PC2) indicates one-locus SI. Two to four compatible/incompatible clusters found in the analyzed diallels is in accord with a GSI type. More interestingly, the biplots also showed varying degrees of interaction between plants as females (pollen receiving) and plants as males (pollen donors) in the data from two diallels. The biplot method offers an alternative approach to study the genetic control of self-incompatibility via diallel crosses, and we propose that it might be particularly useful to study complex self-incompatibility systems in which conventional methods for the analysis of sib diallel results have proven difficult.