Notes on &lt;I&gt;Hymenoscyphus&lt;/I&gt; — 3: On the nomenclature of &lt;I&gt;Hymenoscyphus subcarneus&lt;/I&gt; (&lt;I&gt;Ascomycota, Helotiales&lt;/I&gt;)

Hengstmengel, Jan

doi:10.5248/107.267

Cited by 4 publications

(1 citation statement)

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“…The presence of pigmented spores has been overestimated as a generic character in the Helotiales. As pointed out by Galán and Baral ( 1997 , p. 61) and Hengstmengel ( 2009 , p. 271), this feature of overmature spores is quite a common character in Hymenoscyphus, though it is seen only inconsistently and sometimes very rarely in a given species. The proportion of brown spores in a preparation depends on the senescence of the apothecia.…”

Section: Methodsmentioning

confidence: 86%

Hymenoscyphus fraxineusvs.Hymenoscyphus albidus– A comparative light microscopic study on the causal agent of European ash dieback and related foliicolous, stroma-forming species

Baral¹,

Bemmann²

2014

Mycology

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Five species of Hymenoscyphus that fruit on black stromatized parts of dead leaves of deciduous trees are presented, giving details on their morphological and ecological characteristics. Several of these species have previously been misplaced in rutstroemiaceous genera because of the presence of a substratal stroma. However, the heteropolar, scutuloid ascospores with an often hook-like lateral protrusion at the rounded apex and the ascus apical ring of the Hymenoscyphus-type represent two reliable morphological characteristics that, together with molecular data, provide clear evidence for their placement in the genus Hymenoscyphus (Helotiaceae). Among the species treated is Hymenoscyphus fraxineus (=Hymenoscyphus pseudoalbidus), the causal agent of the European ash dieback disease. Since 1992 this species started within Europe to replace the rather uncommon Hymenoscyphus albidus, which is likewise confined to leaves of Fraxinus. Hy. fraxineus has been recorded already since 1990 in Eastern Asia (Japan, Korea, northeast of China), where it had been initially misidentified as Lambertella albida (≡Hy. albidus). In these regions, it occurs as a harmless saprotroph on Fraxinus mandshurica and Fraxinus rhynchophylla, suggesting that those populations are native while the European ash dieback disease has a recent Eastern Asiatic origin. The distinctly higher genetic diversity found in Japanese Hy. fraxineus in contrast to European Hy. fraxineus supports this view. Genetic similarities between Japanese Hy. fraxineus and European Hy. albidus suggest that also Hy. albidus might be a descendant of Asian Hy. fraxineus, though having invaded Europe much earlier. However, consistent genetic deviation between European and Asian Hy. fraxineus at two nucleotide positions of the ITS region indicates that the European ash disease originates from a region different from the presently known areas in Eastern Asia.Our results underline the importance of detailed morphological studies in combination with molecular work. Hy. fraxineus was described from Europe as a cryptic species that differed from Hy. albidus by molecular data alone. However, the Hy. albidus/Hy. fraxineus species complex represents one of many examples within the ascomycetes in which subtle microscopic differences between closely related species, in this case the presence or absence of croziers at the ascus base, are strictly correlated with molecular characteristics. Two species that closely resemble Hy. albidus and Hy. fraxineus form pseudosclerotia in Aesculus leaves and again differ from each other mainly in the ascus base: Hymenoscyphus aesculi on Aesculus hippocastanum from Europe lacks croziers, whereas Hymenoscyphus honshuanus from Japan on Aesculus turbinata possesses croziers. Other taxa treated here include Hymenoscyphus vacini, a European species growing on stromatized net veins of skeletonized leaves of Acer, and Hymenoscyphus torquatus, a Chinese species on unidentified herbaceous stems. An equivalent stroma-forming North American species on leaves of Fra...

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Section: Methodsmentioning

confidence: 86%