APPLICATION OF SOMATIC EMBRYOGENESIS TO TREE IMPROVEMENT IN CONIFERS

摘要

Somatic embryogenesis (SE) offers advantages in tree breeding due to the genetic gain improvements that can be realized through selection and production of elite (clonal) lines. Additionally, it is a platform through which value-added traits can be introduced via genetic engineering. At CellFor considerable effort has been directed towards the improvement of SE protocols for coniferous species, with significant focus placed on development in vitro. Recent progress includes rapid bulk-up of cultures via liquid culture, production of desiccation-tolerant embryos in bioreactors and direct delivery of somatic seed to the nursery. Additionally, transgenic spruce, loblolly pine and radiata pine have been developed via SE, with the targets including enhanced cellulose synthesis, lignin modification and control of key developmental pathways As a tool for tree improvement, conifer SE circumvents the infrastructure and time constraints that are inherent to production of improved seed via seed orchards. The application of SE in this context necessitates the development of a deployment strategy that addresses genetic diversity and the genetic gain achieved. Approaches, based on the principles of population genetics, have been developed to optimize both the initial selection strategy and subsequent deployment of clonal lines. Since 1995, CellFor and its predecessor companies have implemented commercial programs for spruce (interior; Sitka), pine (loblolly; radiata; slash) and Douglas-fir. Annual volume production in excess of 1 million seedlings has been achieved.