Crossing Success in Abies nordmanniana Following Artificial Pollination With a Pollen Mixture of A. nordmanniana and A. alba

Controlled crossings were conducted with three Abies nordmanniana genotypes acting as mothers and a pollen mixture of three Abies nordmanniana genotypes and one Abies alba genotype acting as potential fathers. The aim was to investigate hybridization success under circumstances where pollen from both species are present, which is a potential risk in Danish clonal seed orchards of Abies nordmanniana. The number of seeds sired by each father was determined through SSRs and compared to the expected numbers based on the pollen mixture composition. All three mother genotypes of Abies nordmanniana had more progenies with the Abies alba as father (hybrids) than expected, based on proportions in the pollen mix. This indicates that no reproductive barriers between the two species exist, and that seed orchard managers should take precautions to avoid hybrids in seed crops. Furthermore, the experiments revealed quite different siring success of the three Abies nordmanniana genotypes, depending on which clone was the mother. Abies nordmanniana seed orchards should therefore not be established in the vicinity of Abies alba in the flowering age, and if a few-clone set up is chosen, the mating interaction should be investigated beforehand through pollen mix experiments.