This article argues that "genetic modernism" in seeds was simultaneously a technoscientific and a political project that materialized under wartime Vichy's proto-fascist regime and that contributed to shaping and legitimizing Vichy as a "planner state." The constitution of the genetically homogeneous cultivar as a scientific object, a market commodity, and a state policy object went hand in hand during the Vichy regime. A new biopolitical connection between state and seeds emerged, in which seeds were considered a priority target for state intervention because they were seen as the easiest path toward transforming agricultural practices so as to meet pressing needs for a sufficient and autonomous food supply (autarky). The state acquired the power of life and death over plant genomes in the nation's landscapes and enacted a phytoeugenics that was both positive (aiming to encourage the diffusion of varieties deemed healthy or higher yielding) and negative (aiming to suppress varieties deemed obsolete). The ontology of "genetic modernism" considered living beings as having an intrinsic genetic identity, sealed off from the vagaries of the environment, and favored serial and stable forms of life, which were achieved materially through the production of plant populations composed of isogenotypic individuals (clones, pure lines, F1 hybrids). Such pure line ontology, planned seed-economy practices, and metrological arrangements articulated a biopolitics geared towards superseding a nexus of biocultural crop evolutionary processes under farmers' management with centralized planning of genetic progress. This turned Vichy France into a huge biopolitical laboratory. It also left major legacies in the post––World War II decades.