Self-incompatibility is a common mechanism by which flowering plants can ex
ert some control over the process of fertilization. Typically, the self-inc
ompatibility response involves the recognition and rejection of self-incomp
atible pollen which leads to a block in self-fertilization and, as a conseq
uence, promotes outcrossing. In recent years, considerable progress has bee
n made in the molecular understanding of several self-incompatibility syste
ms. Interestingly, a common mechanism for self-incompatibility is not emplo
yed by all flowering plants, but in fact quite diverse mechanisms have been
recruited for the rejection of self-incompatible pollen. In this review, t
he recent advances in the self-incompatibility systems of the Solanaceae, P
apaveraceae, and Brassicaceae will be described as well as some of the mole
cular work that is emerging for the Poaceae and the heteromorphic self-inco
mpatibility systems.