Regulation and Management of Cone Induction in Temperate Conifers

Abstract

Forest tree improvement programs provide the basis for most of our knowledge of cone induction in conifers. Since World War II, forest geneticists and tree breeders have largely selected for traits that improve productivity, and improved seed is now commonly produced in seed orchards. However, seed production in many conifers varies widely from year to year, regulated in part by environmental conditions. Therefore, much of the research in conifer reproduction has focused on enhancement of cone development during summers when weather conditions are unfavorable to reproductive bud initiation. In this review, we synthesize current knowledge about the manipulation of cone production in temperate conifers. We provide an overview of conifer reproductive biology, describe the progression from reproductive incompetence to reproductive maturity, and discuss both endogenous (e.g., genetic, epigenetic, hormonal) and exogenous (e.g., temperature, moisture, tree size) regulation of reproductive development. Finally, we summarize the most common approaches to cone enhancement in seed orchards, provide direction for future research, and suggest possible mechanisms that might govern reproductive development, such as the GA-DELLA and miR156