Private investment in plant breeding has been increasing while public plant breeding has stagnated or declined. Moreover, research investment among crop commodities is uneven. Using a comprehensive survey of U.S. plant breeders from 1994, we use a simultaneous equations model to examine incentives and public-private tradeoffs in plant breeding research among 84 crop commodities. Allocation of private breeders among crops is strongly influenced by market size, hybrid seed technology, and ease of breeding improvement. In general, the allocation of public breeders does not appear to "crowd out" private breeders, but some competition may occur in applied breeding. Public breeding declines as private breeding increases on a commodity. Public breeding is also affected by market size, ease of breeding improvement, and political influence.