Plant Cell Reports

, Volume 22, Issue 2, pp 96–104 | Cite as

Brassinolide improves embryogenic tissue initiation in conifers and rice

  • G. S. Pullman
  • Y. Zhang
  • B. H. Phan
Cell Biology and Morphogenesis


Somatic embryogenesis (SE), the most promising technology for the large-scale production of high-value coniferous trees from advanced breeding and genetic engineering programs, is expected to play an important role in increasing productivity, sustainability, and the uniformity of future U.S. forests. To be successful for commercial use, SE technology must work with a variety of genetically diverse trees. Initiation in loblolly pine (Pinus taeda L.), our main focus species, is often recalcitrant for desirable genotypes. Initiation percentages of loblolly pine, Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco], and Norway spruce (Picea abies L., Karst.) were improved through the use of brassinolide. Brassinosteroids, which include brassinolide, are a relatively new group of natural plant growth regulators that are found in many plant species. They have been shown to have diverse, tissue-specific, and species-specific effects, including the stimulation of cell elongation and ethylene production and increasing resistance to abiotic stress. In our media, brassinolide was effective at concentrations ranging from 0.005–0.25 μM. Using control medium (no brassinolide) and brassinolide-supplemented (0.1 μM) medium, we achieved improved initiation percentages in loblolly pine, Douglas-fir, Norway spruce, and rice—15.0% to 30.1%, 16.1% to 36.3%, 34.6% to 47.4%, and 10%, respectively. Brassinolide increased the weight of loblolly pine embryogenic tissue by 66% and stimulated initiation in the more recalcitrant families of loblolly pine and Douglas-fir, thus compensating somewhat for genotypic differences in initiation. Initiation percentages in loblolly pine were improved through the combination of modified 1/2-P6 salts, 50 mg/l activated carbon (AC), adjusted levels of Cu and Zn (to compensate for adsorption by AC), 1.5% maltose, 2% myo-inositol (to raise the osmotic level, partially simulating the megagametophyte environment), 500 mg/l casamino acids, 450 mg/l glutamine, 2 mg/l α-naphthaleneacetic acid, 0.63 mg/l 6-benzylaminopurine, 0.61 mg/l kinetin, 3.4 mg/l silver nitrate, 10 μM cGMP, 0.1 μM brassinolide, and 2 g/l Gelrite. Across 12 open-pollinated families of loblolly pine, initiation percentages ranged from 2.5% to 50.7%, averaging 22.5%.


Brassinosteroids Loblolly pine Somatic embryogenesis Initiation Pinus taeda 



Activated carbon




Guanosine 3′,5′-cyclic monophosphate, 8-bromo-, sodium salt


2,4-Dichlorophenyloxyacetic acid


α-Naphthaleneacetic acid



We thank the member companies of IPST for financial support and Boise Cascade, Champion (now International Paper Company), Mead (now MeadWestvaco), International Paper Company, The Timber Company, Union Camp (now International Paper Company), Westvaco (now MeadWestvaco), and Weyerhaeuser Company for cones. We are grateful for the help of R. Gupta, J. Halpin, R. Howie, S. Johnson, E. Muhlberger, and K. Wong. We thank Dr. Gary Peter for discussions concerning potential auxin or cytokinin signaling compounds.


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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  1. 1.Institute of Paper Science and TechnologyAtlantaUSA
  2. 2.Center for Applied Genetic TechnologyThe University of GeorgiaAthensUSA

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