Genetic analysis of inherited reduced susceptibility of Fraxinus excelsior L. seedlings in Austria to ash dieback

514–525

Artikel aus einer Zeitschrift

200204465

Forestry 2018 : e-only : Journal of the Institute of Chartered Foresters ; Jrg. 91 ; 2 (2018) , 514–525

Hymenoscyphus fraxineus causes massive dieback of common ash (Fraxinus excelsior L.) across populations. Previous common garden trials have revealed differences in susceptibility among individuals, suggesting a genetic basis for reduced susceptibility to the pathogen. The aim of the study was to identify any correlation between damage intensity of mature trees and their offspring in natural ash stands. Crown and shoot damage of naturally infected trees and saplings were assessed in two geographically isolated stands in Austria, and parentage analysis was carried out with molecular markers. No significant correlation could be detected using Spearman’s rank correlation analysis, suggesting that this approach would need higher numbers of adult–offspring pairs present to compensate for environmental and genetic variability at the sites. Likewise, an in situ estimate of heritability was nearly zero. The results thus support the results of other studies, i.e. that highly resistant individuals occur only at low frequency within European ash populations. While most of the previous studies were conducted in progeny trails or seed orchards and suggested a fairly strong genetic component, results from our investigation support a more complex mechanism of susceptibility differences under natural, heterogeneous conditions. Further analyses are needed to obtain a better understanding of gene–environment interactions and individual infection pressure of ash dieback in natural environments; such studies would need to be based on much higher sample numbers. Identification and propagating of non-susceptible ash trees is an important challenge to halt large-scale dieback of common ash.