ISOZYME GENETIC-VARIATION AND HETEROZYGOSITY IN RANDOM TREE SAMPLES AND SELECTED ORCHARD CLONES FROM THE SAME NORWAY SPRUCE POPULATIONS

The genetic implications of plus-tree selection were studied in Norway spruce (Picea abies) with the aid of isozyme gene markers. For this purpose, 45 phenotypically selected seed orchard clones and 60 randomly chosen trees from the same Bavarian forest districts were compared with respect to their genetic structure, gene diversity and heterozygosity at eight enzyme gene loci. In general, the gene frequency distributions, the gene multiplicity and the gene diversity did not significantly differ between the selected clone (plus-tree) collection and the random tree sample; however, the average degree of heterozygosity and the distribution of individual heterozygosity clearly differed between the two collections. The most significant differences in heterozygosity between the two collections were observed in the case of three loci controlling enzymes involved in the pentose phosphate cycle. The implications of these results for tree improvement procedures, establishment of seed orchards and programmes in gene conservation are discussed.