High tree mortality rates are found in ash forests as a consequence of the action of the pathogen ( Coker et al., 2019). fraxineus to colonize living tissue in ash is the key to its success as a pathogen. Alternatively, conditions of high humidity and high infection pressure ( Havrdová et al., 2017) enable the pathogen to directly infect stem collars at ground level and cause the trees to collapse from the base ( Chandelier et al., 2016 Enderle et al., 2017), perhaps through the direct infection of stem lenticels ( Nemesio-Gorriz et al., 2019). Over a number of years, this process results in crown loss and eventual death of ash trees ( Gross et al., 2014). The pathogen infects the leaves of the host and translocates through the leaf rachis and petiole into the shoot, which leads to crown dieback. excelsior, with the exception of some areas in Southern and Western Europe. Today, its distribution overlaps with most of the natural distribution of F. Hymenoscyphus fraxineus was introduced in Europe and was first described in F. In recent decades, European common ash ( Fraxinus excelsior) has been severely affected by ash dieback (ADB) disease, caused by the invasive fungal pathogen Hymenoscyphus fraxineus ( Baral et al., 2014) it also infects narrow-leaved ash ( F. Our findings indicate the presence of constitutive chemical defense barriers against ash dieback in ash.Īsh dieback, chemotype, coumarin, Fraxinus, Hymenoscyphus, secoiridoid, tolerance Introduction Similarly, fungal growth inhibition was observed when the methanolic bark extract of low-susceptibility ash genotypes was supplied. fraxineus in vitro when supplied at physiological concentrations, thereby validating their role as markers for low susceptibility to ash dieback. Both coumarins inhibited the growth of H. Increased levels of two coumarins, fraxetin and esculetin, were strongly associated with reduced susceptibility to ash dieback. A total of 64 candidate metabolites associated with reduced or increased susceptibility in the chemical families secoiridoids, coumarins, flavonoids, phenylethanoids, and lignans.
This revealed two significantly different chemotypes. We compared the metabolomes from a cohort of low-susceptibility ash genotypes with a cohort of high-susceptibility ash genotypes. Within Fraxinus excelsior populations, a small proportion of genotypes show a low susceptibility to the pathogen. Ash dieback, a forest epidemic caused by the invasive fungus Hymenoscyphus fraxineus, threatens ash trees throughout Europe.
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