Genetic variation and genotype by environment interaction in the susceptibility of Abies nordmanniana (Steven) Spach to the fungus Neonectria neomacrospora (Booth & Samuels) Mantiri & Samuels

Key message Pronounced clonal variation and moderate to high broad-sense heritability estimates of susceptibility to Neonectria neomacrospora were found in Abies nordmanniana in three sites. Significant genotype by environment (G × E) interaction was detected across sites. Context Nordmann fir, a widely used Christmas tree species in Europe, has, since 2011, been increasingly damaged by a canker disease caused by Neonectria neomacrospora . Aims The objective was to study the genetic variation and genotype by environment interaction in the susceptibility of Nordmann fir to N. neomacrospora . Methods Damage caused by N. neomacrospora was evaluated using a visual scale in three Nordmann fir clonal seed orchards in Denmark, partly containing the same clones. Results Damage due to N. neomacrospora was substantial at all three sites, and no clone was completely resistant to N. neomacrospora , but a large genetic variation in the susceptibility was detected among clones. Estimates of single-site individual broad-sense heritability for susceptibility varied between 0.38 and 0.47. The average type-B genetic correlation for damage score across sites was 0.34. Conclusion Genetic variation was very pronounced, and significant G × E interactions were detected for susceptibility. Further investigations of narrow-sense heritability, expression of the trait in younger material, and identification of the cause of G × E for N. neomacrospora susceptibility in Nordmann fir across different sites are recommended.