Canadian Forest Service Publications

Is there potential for propagation of adult spruce trees through somatic embryogenesis? 2016. Klimaszewska, K.; Rutledge, R.G. Pages 195-210 in Park, Y.-S.; Bonga, J.M.; Moon, H.-K., eds. Vegetative Propagation of Forest Trees, National Institute of Forest Science, Seoul, Korea.

Year: 2016

Available from: Laurentian Forestry Centre

Catalog ID: 36686

Language: English

CFS Availability: PDF (request by e-mail)

Abstract

Although large-scale cloning of elite adult conifer trees via somatic embryogenesis (SE) has long been a holy grail for many tree improvement programs, attempts by a number of research groups to induce embryonal tissues from vegetative explants has, to date, produced very limited success. It has been speculated that this recalcitrance is related to (potentially reversible) epigenetic suppression of the embryogenicity that underpins SE induction, for example, within zygotic embryos. However, our limited understanding of the molecular mechanisms contributing to SE induction, particularly within conifers, provides little support for such a supposition. Exacerbated by a paucity of responsive vegetative explants, the discovery of a clonal line (G6) of somatic embryo-derived white spruce (Picea glauca) trees whose primordial shoots have remained responsive to SE induction for well over a decade, presented an outstanding opportunity to explore SE-induction at a genomic level via transcriptome analysis. Subsequent screening further revealed that some of these G6 trees had lost responsiveness, further presenting an opportunity to conduct gene expression analysis under an epigenetic context. That was done in the absence of genotypespecific factors which, as described here, confound identification of genes directly involved in SE-induction responsiveness. This chapter describes the origin of these somatic trees and of the extensive SE induction experimentation conducted over the last five years, including microscopic analysis of the tissues generated. In addition we describe absolute qPCR analysis comparing gene expression within responsive and nonresponsive G6 explants, and ending with a brief overview of recent efforts to apply RNA-seq analysis.

Plain Language Summary

This chapter describes the progress made in cloning adult white spruce trees through somatic embryogenesis from vegetative tissues (shoot buds). If adult/mature trees with desired characteristics could be multiplied and planted, it would accelerate the breeding cycle, which would greatly benefit the forest industry.

Somatic embryogenesis is a biotechnology that makes possible the multiplication (cloning) of a single seed embryo into a huge number of somatic embryos that grow into plants. Conifer seeds have been cloned, but somatic embryogenesis has yet to be induced in mature trees.

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