Is floral structure a reliable indicator of breeding system in the Brassicaceae?

Abstract

This study investigated the usefulness of floral characters as a potential indicator of breeding system in the Brassicaceae. Initially, pod set, seed set and pollen tube growth experiments were carried out to confirm the breeding systems of 53 lines representing 25 different cultivated and weedy species from the Brassicaceae. The results of the pod set tests clearly differentiated between self-compatible and self-incompatible species. Floral characters were then evaluated on one or more lines of each of the 25 species. Fourteen floral characters were evaluated including, flower diameter, Cruden's outcrossing index, timing and direction of dehiscence and pollen-ovule ratio. Significant differences between species were evident in all of the floral characteristics evaluated. Flower diameter was generally larger in self-incompatible species than self-compatible species and pollen/ovule ratio was generally higher in self-incompatible species than self-compatible species. However, none of the floral characteristics was able to clearly differentiate the self-compatible and self-incompatible species and allow prediction of the breeding system with absolute confidence. The floral characteristic which was most effective at differentiating the two groups was anther direction at dehiscence.