Seed orchard genetics

Seed orchards represent the link between tree breeding and silvicultural activities. Their genetic efficiency is of vital importance as it determines the extent of genetic gain and diversity of future forest tree plantations. Given their importance, seed orchard genetics has received increased scientific and managerial scrutiny. Virtually all aspects affecting seed orchard genetic efficiency have been thoroughly investigated, including their biological model, underpinning assumptions and management practices developed and implemented to improve crop genetic quality. In this review, we systematically address these topics starting with the position of seed orchards in the tree improvement cycle, their population genetics model and the biological factors affecting this model; namely, reproductive investment and success, reproductive phenology, inbreeding, gene flow and finally the biology of the seed. Management practices are reviewed including those implemented during the establishment phase (orchard size, design, number of parents and their representation) and those implemented for enhanced crop management (crown management, supplemental mass pollination, bloom delay, selective seed harvesting and the production of designer crops). The genetic consequences of these issues are discussed. The intention of this article is to produce a state-of-art review of this vital component of every tree improvement delivery system and to facilitate and encourage further research and development for present and future seed orchards.