Male fertility requires a number of coordinated developmental events. These include the formation, as part of the flower, of stamens and anthers from the vegetative meristem; the development of pollen grains inside the anther locules; the timely release and deposition of pollen on the stigma; and finally, in self-compatible plants, the interaction of the male and female gametes to attain self-fertilization. Mutations can be obtained that perturb any of the above processes, giving rise to a plant with impaired pollen function but normal female fertility. Such mutations in self-compatible plants have been described as male steriles (ms).