RELATIONSHIP BETWEEN NUCLEAR-DNA MARKERS AND PHYSIOLOGICAL-PARAMETERSIN SITKA X INTERIOR SPRUCE POPULATIONS

Eight populations of Sitka spruce (Picea sitchensis (Bong.) Carr.) and interior spruce (Picea glauca (Moench) Voss x Picea engelmannii Parry ex. Engelm.) seedlings were sampled from a zone of Sitka-interior spr uce introgression in British Columbia, Canada. Restriction fragment le ngth polymorphisms of the nuclear ribosomal RNA genes (rDNA) were used to define species-specific hybridization patterns for the Sitka spruc e and interior spruce populations. Hybridization was estimated from an index based on the relative abundance of polymorphic rDNA combining b ands for each population. Sitka x interior hybrid seedlings had an ind ex 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 elongat ion, osmotic potential at saturation (Psi(sat)) and turgor loss point (Psi(tlp)) increased, whereas total turgor (Psi(PTotal)) decreased. Af ter bud set in the summer and throughout the fall, Psi(sat) and Psi(tl p) decreased, whereas Psi(PTotal) increased. At all times of year, pop ulations with a higher Si-rDNA index had lower Psi(tlp) and Psi(sat) a nd higher Psi(PTotal) than populations with a lower Si-rDNA index. Dur ing the fall, Sitka x interior hybrid seedlings exhibited a seasonal d ecline in the temperature causing 50% needle electrolyte leakage (LT(5 0)) and in the critical temperature indicating the initial point of fr eezing injury. Seedlings with a higher Si-rDNA index had lower LT(50) 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.