ANALYSIS OF SITKA SPRUCE - INTERIOR SPRUCE INTROGRESSION IN BRITISH-COLUMBIA USING CYTOPLASMIC AND NUCLEAR-DNA PROBES

Restriction fragment length polymorphisms of the nuclear ribosomal RNA genes were used to define species-specific patterns for interior spru ce (a complex of white spruce, Picea glauca (Moench) Voss, and Engelma nn spruce, Picea engelmannii Parry) and Sitka spruce (Picea sitchensis (Bong.) Carr.) populations in British Columbia. These patterns are hi ghly conserved among seed lots and individual trees of each species fr om diverse geographic origins. Both the ribosomal RNA gene probe and s pecies-specific probes for the chloroplast and mitochondrion, describe d previously, were used to analyze 164 dominant trees from 19 location s in a zone of presumed Sitka-interior spruce introgression in northwe stern British Columbia. Hybrid fraction was estimated from an index ba sed on the relative abundance of polymorphic ribosomal RNA hybridizing bands for each tree and was in good agreement with the proportion of trees exhibiting either interior or Sitka spruce specific chloroplast bands. The results demonstrate that complex hybrids occur frequently i n this zone, indicative of true introgression. Furthermore, the trend of variation in species mix is consistent with the topographical trend s. It is anticipated that the results of this survey will be useful in defining seed transfer guidelines for reforestation of this region.