Genetics and genetic modifications of plant architecture in grain legumes: a review

Crop architecture may be modified to improve the adaptation of the crops to different environments and to increase the seed yield and its stability. The main peculiarities of the grain legume architecture are the indeterminate growth habit, which may lead to a prolonged growth cycle with consequences on the maturation and strong within-plant competition between the reproductive and vegetative growth and the fleshy pods. The principal reasons are presented as to why modifications of the grain legume architecture and the genetic strategies could contribute to increasing the seed yield. The main components of the crop architecture are analyzed. The flowering date is of major importance for the adaptation of a crop to the environmental conditions. The branching pattern may be directly affected independently of other architectural modifications. The leaf size and structure contribute to the leaf area index of the crop and may influence the light interception efficiency. The determinate growth habit modifies the duration of the growth cycle and the assimilate partitioning while the dwarfism may improve the adaptation to a range of environments through the reduction of the lodging risk. The pod walls may contribute to the pod photosynthesis but they account for a large proportion of the pod weight at harvest. This reduces the crop harvest index. For each of these traits, the genetic modifications that have been observed in the different grain legume species are presented as well as their genetic control. The consequences on the seed yield elaboration and the adaptation of the crops are assessed. The limitations of the architectural modifications are also investigated and the interest in combining morphogenetic and functional approaches is discussed. ((C) Inra/Elsevier, Paris.).