Genetic male sterility
Genetic male sterility is very effective, but a sophisticated set-up is needed to maintain the male sterile stock. So the choice of female parent tends to be very restricted.
The easiest form of genetic male sterility to handle is that induced by either a particular daylength or temperature regime. This form is used to make most of the F1 hybrid rice seed. (See Zhang et al. (1994) Field Crops Research 38: 111-120.)