Rapid changes in property rights protection with respect to agricultural genetic resources require careful policy evaluation on their possible effects to private crop breeders as well as to society. Using a stylized model of cumulative innovation, we explore the dynamics of introduction of patent protection with licensing agreements, and contrast the results with the comparative statics viewpoint. We also investigate the dynamic effects of a strong form of claims on behalf of farmers' rights on the profits of private crop breeders whose output is newly protected by patents. We show that the choices of patent life and royalty rate that optimize worldwide dynamic social welfare can be quite different from the values that maximize the steady-state social welfare. While the steady-state social welfare is in general reduced from a stronger protection, the dynamic social welfare may turn out to be increased since the benefit from early first innovation can dominate the slow-down of the steady-state innovations. We also show that recognition of farmers' rights entails a dynamic welfare loss to producers and consumers not revealed in a comparative statics analysis.