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<p>Ash dieback (ADB), caused by the invasive alien fungal pathogen <i>Hymenoscyphus fraxineus</i>, is a disease that poses major threats to the survival of common ash (<i>Fraxinus excelsior</i>) in Europe. Here, we report on a field trial aiming at the identification of ADB tolerant genotypes while encompassing the genetic diversity of common ash in Austria. Over 35,000 progenies from 611 putatively tolerant mother trees and a selection of 71 clones from two clonal seed orchards were assessed for ADB symptoms over a period of three years. One tolerant and one susceptible progeny from a subset of the mother tree range (570 trees) were genotyped using the 4TREE array, a genotyping tool developed specifically to screen common ash populations for their tolerance to ADB. We aimed to (1) better characterize the genetic structure of common ash in Austria and identify hybrids between common ash and <i>F. angustifolia</i> (narrow-leaved ash) (2) detect genetic loci associated with tolerance to ADB, and (3) identify genetic variation associated with abiotic factors such as precipitation and altitude influencing the severity of ADB. We identified ash individuals from Eastern Austria matching putative hybrids with <i>F. angustifolia</i> showing varying degrees of <i>F. angustifolia</i> ancestry in structure analyses<i>.</i> The non-hybrid gene pool was characterized by shallow genetic structure following a west to east geographic pattern. In contrast to our expectations, genotype-damage association analyses failed to detect SNPs associated with tolerance to ADB. Our findings underscore that the polygenic architecture governing tolerance and the rapid decay of genomic linkage disequilibrium (LD) (within approximately 23&#xa0;kb) significantly limit the ability to identify association outliers using the 4TREE array. This highlights the constrained utility of chip genotyping approaches for this specific purpose. In contrast, the array proved successful in detecting hybrids between common ash and narrow-leaved ash, as well as SNPs associated with abiotic predictors (such as annual precipitation) suggesting local environmental adaptation of common ash genotypes.</p>

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Limitations of ad hoc genotyping in detecting ash dieback tolerance in Fraxinus excelsior

  • 期刊论文

  • 发表日期：

    2025年12月3日

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  • Aglaia Szukala,
  • Gregor M. Unger,
  • Carlos Trujillo-Moya,
  • Thomas Geburek,
  • Thomas Kirisits,
  • Silvio Schueler,
  • Heino Konrad

摘要

Ash dieback (ADB), caused by the invasive alien fungal pathogen Hymenoscyphus fraxineus, is a disease that poses major threats to the survival of common ash (Fraxinus excelsior) in Europe. Here, we report on a field trial aiming at the identification of ADB tolerant genotypes while encompassing the genetic diversity of common ash in Austria. Over 35,000 progenies from 611 putatively tolerant mother trees and a selection of 71 clones from two clonal seed orchards were assessed for ADB symptoms over a period of three years. One tolerant and one susceptible progeny from a subset of the mother tree range (570 trees) were genotyped using the 4TREE array, a genotyping tool developed specifically to screen common ash populations for their tolerance to ADB. We aimed to (1) better characterize the genetic structure of common ash in Austria and identify hybrids between common ash and F. angustifolia (narrow-leaved ash) (2) detect genetic loci associated with tolerance to ADB, and (3) identify genetic variation associated with abiotic factors such as precipitation and altitude influencing the severity of ADB. We identified ash individuals from Eastern Austria matching putative hybrids with F. angustifolia showing varying degrees of F. angustifolia ancestry in structure analyses. The non-hybrid gene pool was characterized by shallow genetic structure following a west to east geographic pattern. In contrast to our expectations, genotype-damage association analyses failed to detect SNPs associated with tolerance to ADB. Our findings underscore that the polygenic architecture governing tolerance and the rapid decay of genomic linkage disequilibrium (LD) (within approximately 23 kb) significantly limit the ability to identify association outliers using the 4TREE array. This highlights the constrained utility of chip genotyping approaches for this specific purpose. In contrast, the array proved successful in detecting hybrids between common ash and narrow-leaved ash, as well as SNPs associated with abiotic predictors (such as annual precipitation) suggesting local environmental adaptation of common ash genotypes.