Microsatellite analysis of maternal half-sib families of Quercus robur, pedunculate oak: detection of seed contaminations and inference of the seed parents from the offspring

Abstract

Microsatellites were used for genetic analysis of maternal half-sib families of Quercus robur, pedunculate oak, a highly outcrossing tree species. A model half-sib family including the mother tree and 28 offspring individuals as well as samples from six single tree harvests from a forestry company, 4–8 individuals each, were genotyped at 9 microsatellite loci. No prior information about the genotypes of the mother trees were available for these six seedlot samples. Analysis of the model half-sib family revealed that the maternal genotypes can be inferred from the offspring genotypes due to codominant Mendelian inheritance of the microsatellites. Analysis of the single tree harvests, supplied as six maternal half-sib families, revealed contaminations with unrelated seedlings in four out of six cases. Average relatedness between the remaining individuals indicated that they were indeed half-sibs, probably with a proportion of full-sibs among them. For five samples the genotypes of the mother trees were partially inferred from the offspring genotypes. The supposed number of five different mother trees was confirmed by direct comparison of the maternal genotypes and by pairwise FST calculations between families. We show that correct genotype reconstruction can be confirmed by monitoring recombination events between linked markers. Our results demonstrate that microsatellite analysis is a suitable means to approach two key problems of legal regulations on the marketing of seed material from pedunculate oak: the number of trees included in seed harvests and the detection of seed contaminations.