Seeds are a major means for transforming farming systems and thus occupy a prominent place in the transition to more sustainable agriculture. This article analyses the conditions involved in creating and diffusing new plant breeds that have agroecological benefits, called eco-innovation varieties. By combining theories on eco-innovation processes with various scales of analysis, this study makes an original contribution to understanding innovation and transformation dynamics in the seed industry. Drawing on a case study of the sunflower industry in France and in Europe, the findings reveal which factors promote and hinder eco-innovation varieties. The results confirm the positive interactions between technology, regulation, and the market in eco-innovation processes. They also show that economic incentives for companies are insufficient to push them to develop more systemic eco-innovation varieties. Moreover, changes in the mainstream seed company regime, with the increasing internationalization of their strategies, call into question their ability to foster farming practices that promote the environmental benefits of these new varieties.