Relationship between nuclear DNA markers and physiological parameters in Sitka × interior spruce populations

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Tree Physiology, 16:547–555

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Relationship between nuclear DNA markers and physiological parameters in Sitka × interior spruce populations

Steven C. Grossnickle, Ben C. S. Sutton, Raymund S. Folk and Robert J. Gawley

Forest Biotechnology Centre, B.C. Research Inc., 3650 Wesbrook Mall, Vancouver, B.C. V6S 2L2, Canada / Received March 7, 1995

Summary

Eight populations of Sitka spruce (Picea sitchensis (Bong.) Carr.) and interior spruce (Picea glauca (Moench) Voss × Picea engelmannii Parry ex. Engelm.) seedlings were sampled from a zone of Sitka–interior spruce introgression in British Columbia, Canada. Restriction fragment length polymorphisms of the nuclear ribosomal RNA genes (rDNA) were used to define species-specific hybridization patterns for the Sitka spruce and interior spruce populations. Hybridization was estimated from an index based on the relative abundance of polymorphic rDNA combining bands for each population. Sitka × interior hybrid seedlings had an index value for the relative abundance of interior spruce rDNA (Si-rDNA) ranging from 0.07 (Lower Nass; the most westerly collected source) to 0.95 (Bulkley Valley low-elevation seed orchard). During shoot elongation, osmotic potential at saturation (Ψ_sat) and turgor loss point (Ψ_tlp) increased, whereas total turgor (Ψ_PTotal) decreased. After bud set in the summer and throughout the fall, Ψ_sat and Ψ_tlp decreased, whereas Ψ_PTotal increased. At all times of year, populations with a higher Si-rDNA index had lower Ψ_tlp and Ψ_sat and higher Ψ_PTotal than populations with a lower Si-rDNA index. During the fall, Sitka × interior hybrid seedlings exhibited a seasonal decline in the temperature causing 50% needle electrolyte leakage (LT₅₀) and in the critical temperature indicating the initial point of freezing injury. Seedlings with a higher Si-rDNA index had lower LT₅₀ and critical temperature values indicating greater freezing tolerance in the fall. Throughout most of the year, seedling population Si-rDNA index was related to the degree of drought and freezing tolerance.

Keywords: freezing tolerance, nuclear DNA markers, Picea engelmannii, Picea glauca, Picea sitchensis, water relations parameters.