Genetic identification of clones and the genetic structure of seed crops in a Pinus brutia seed orchard

摘要

Megagametophyte tissue in seeds from a Pinus bruia Ten. seed orchard was analyzed for 9 enzyme systems (aconitase, alcohol dehydrogenase, glutamate dehydrogenase, glutamate oxaloacetate-transaminase, malate dehydrogenase, menadione reductase, 6-phosphogluconate dehydrogenase, phosphoglucose isomerase, and shikimate dehydrogenase) encoded by 14 loci using starch gel electrophoresis. Twenty-eight clones and 3 ramets per clone were sampled from the orchard for analysis. Isozyme patterns of the clones clearly indicate that each clone had a different genotype when overall loci were taken into consideration. In 5 of the 28 clones, 1 of the 3 ramets did not match the other 2 ramets at 2 or more loci. This indicates that about 6% of the studied ramets in the seed orchard were mislabeled during and/or before being planted in the orchard. The Adh2-l allele was unique to clone no. 14; therefore, such an allele could be used to determine the extent to which a specific clone contributes to the seed crop. Of the14 loci studied, 7 (50%) were polymorphic (0.95 criterion). Overall, 28 alleles were observed in the orchard trees and seed crops. Three of the 28 alleles (allele 2 at Aco, allele 2 at Gotl, and allele 3 at Pgi2) were not observed in the orchard clones,but were observed only in the orchard seed crops, which indicates that these alleles originated from outside pollen sources. Important allelic differences were noted between the gene pool of the orchard clones and the gene pool of the orchard seed crops, most probably due to the presence of these alien alleles in the orchard crops. We also observed that there was 14.3%, 4.2%, and 13.5% deficiency of heterozygotes at Mnr2, Pgd3, and Sdhl loci, respectively, in the orchard seed crops. Deficiency of heterozygosity could be the result of the Wahlund effect, positive assortative mating, and/or selection for homozygotes and mating among relatives, either alone or in combination.