Restriction fragment variation in the nuclear ribosomal DNA repeat unit within and between Picearubens and Piceamariana

Abstract

The frequencies of polymorphic restriction fragments for the nuclear ribosomal DNA repeat were compared for 12 provenances of red spruce (Picearubens Sarg.) and 34 provenances of black spruce (Piceamariana (Mill.) B.S.P.). Within an individual as many as five distinct ribosomal DNA repeat unit types could be distinguished. Canonical correlation analysis revealed significant variation of restriction fragment frequencies with a geographic variate comprising latitude and longitude of provenances. Geographic origins accounted for 24.7% of the variation in polymorphic restriction fragments in black spruce and 31.8% of the variation in polymorphic restriction fragments in red spruce. Discriminant analysis, using the restriction fragment frequencies for the ribosomal DNA, was used to develop a classification model for the two species. Tenfold verification of the model produced an average correct classification of 99% for black spruce and 96% for red spruce. Plots of canonical scores for the first and second canonical variâtes clearly separated red spruce from black spruce. This study presents a novel combination of restriction fragment frequency data and multivariate analysis to distinguish species that may not always be differentiated using morphological traits.