As on other grain legumes, the determinate architecture seemed promising to reduce vegetative development and improve seed yield and yield stability in autumn-sown white lupin (Lupinus albus). The consequences of this architecture on plant development and yield elaboration was studied through genetic and physiological approaches. The inheritance of determinate architecture was shown to be monogenic and recessive, which allows an easy management of this character in plant breeding. Vegetative development was reduced, because all buds became floral early in the season. Each branch carried fewer leaves than in indeterminates, and the number of vegetative levels was reduced. The profils of number of leaves on the branches had a characteristic bell shape. This structure of branches was modelled. A large genetic variability existed for the architecture, even if the relationship between flowering earliness and vegetative development was strong. Light interception by canopy in terms of thermal time from sowing was similar for the determinates and the indeterminates. Proportion of light reaching the mainstem leaves was higher. Seed yield of determinate genotypes was similar to that of indeterminate genotypes. Dry matter production was lower but harvest index higher than for indeterminates. Maturity date was earlier, especially on cool, wet climates, and yield stability was increased. These trends were linked to the reduction of vegetative development, and to a lower competition between vegetative and reproductive developments than observed in indeterminates. Mainstem and first-order branches mainly contributed to total seed yield, and these orders were less influenced by climatic variation tha upper branch orders. Genetic variability for yield components was large. An extremely reduced vegetative development as well as an excessive development were detrimental to yield. Traits related to branch development (number of leaves and number of branch orders) are valuable breeding criteria on determinate lupins.
