Identyfing alien genotypes and their consequences for genetic variation in clonal seed orchards of pinus sylvestris

Abstract

This study investigates the rates of grafting and planting errors that occur in seed orchards, and evaluates their effects on the genetic diversity and relatedness of genotypes. The study used three clonal Scots pine seed orchards of differing ages and clonal composition located in the forest districts of Susz, Pniewy and Zdrojowa Góra, Poland. Maximum breeding ability within a seed orchard requires isolated from external sources of pollen, and have no alien genotypes inside the orchard. We used 13 isoenzyme markers to determine the genotypic identity of ramets and compared the number of genotypes of the actual current ramet population (W1) with genotypes comprising the originally intended plus trees (designated as W0) to estimate the genotypic assignment error rate per orchard. For both W0 and W1, we calculated the effective number of clones and the relative effective number of clones. Ramet assignment errors were detected in all three seed orchards. Gnotypic errors ranged from 5.8% to 37.7% across orchards. A total of 46 alleles were found, with the mean number of alleles per locus ranging from 2.77 to 3.23. At individual loci, the level of observed heterozygosity was variable. Alien genotypes had negligible effects on seed orchard heterozygosity. The Fst values between seed orchards amounted to 0.6% between Susz and Pniewy and 1.1% between Susz and Zdrojowa Góra. The effect on genetic variation of ramet assignment errors was small and influenced genetic diversity only in the case of the Susz seed orchard. However, our results suggest that negative effects of alien genotypes can occur on breeding value of seeds from analysed seeds orchards.