The main result of this study of patent applications in plant biotechnology showed that a low level of technological differentiation explains a weak regime of appropriability. We consequently propose a complete reversal compared with traditional approaches. Whereas patents are generally considered as a decisive factor, we suggest that alone they cannot induce a dynamic of technological differentiation. It is because they do not play the role attributed to them by Kitch (the co-ordination of actors' plans) that they do not fulfil the function traditionally allocated to them (an incentive to innovation). Given this relation of weak appropriability to a low level of technological differentiation, the dynamics of plant biotechnology seem to be more closely related to the introduction of new tools into specific fields of application via vertical integration, than to the autonomous development of generic technologies. Industrial organization is seen as being characterized by a dynamic of differentiated oligopoly, with a high lever of vertical integration rather than intense horizontal specialization and quasi-commercial relations between firms.