Seasonal development of lesions caused by Hymenoscyphus fraxineus on young Fraxinus excelsior trees in Latvia

The spread of the ascomycete Hymenoscyphus fraxineus, causing dieback of common ash (Fraxinus excelsior) in Europe, is rapid and the damage is pronounced, as young ashes can perish over the course of only a few months following infection. The objective of this study was to investigate the rate and extent of lesion formation on young (5-8-year-old) ashes during a vegetation season in the hemiboreal zone in Latvia. Continuous surveys (with monthly intervals) of the health condition of 30 young ash and measurements of lesion area in three stands were performed during the vegetation season of 2015. From June to September of that year, the number of observed lesions gradually rose from 58 to 87. New lesions emerged on branches (55%, 0.5 per tree), top shoots (28%, 0.3 per tree), and stems (17%, 0.2 per tree), mostly appearing at the beginning of the observation period (45%, 52%, and 3% in June, July, and August, respectively). During the vegetation season, 20% of the existing and 28% of the newly-emerged lesions on branches, as well as 20% and 25% of top shoot lesions, respectively, reached the main stem. Some (< 20% of cases) transitions of lesions from the tops and branches to the stems were observed. The extension of lesions was significant until August, and ceased afterwards in a similar fashion in all stands. The mean extension of area significantly differed between the previously-existing and newly-emerged lesions. During the vegetation season, the new lesions expanded by 25.1 ± 4.8 cm2, whereas the existing ones grew by only 7.3 ± 1.1 cm2. The extension of the new lesions varied according to their location on a tree. The spread of emerging lesions on stems was considerably slower than on branches or top shoots (1.9 ± 0.7, 7.3 ± 1.5, and 14.5 ± 4.1 cm2 per lesion per month, respectively). During the studied vegetation season (summer), the overall health score of trees decreased twice, yet the relationship between heath status and development of lesions lacked significance

Notes for genera – Ascomycota

Knowledge of the relationships and thus the classification of fungi, has developed rapidly with increasingly widespread use of molecular techniques, over the past 10--15 years, and continues to accelerate. Several genera have been found to be polyphyletic, and their generic concepts have subsequently been emended. New names have thus been introduced for species which are phylogenetically distinct from the type species of particular genera. The ending of the separate naming of morphs of the same species in 2011, has also caused changes in fungal generic names. In order to facilitate access to all important changes, it was desirable to compile these in a single document. The present article provides a list of generic names of Ascomycota (approximately 6500 accepted names published to the end of 2016), including those which are lichen-forming. Notes and summaries of the changes since the last edition of `Ainsworth Bisby's Dictionary of the Fungi' in 2008 are provided. The notes include the number of accepted species, classification, type species (with location of the type material), culture availability, life-styles, distribution, and selected publications that have appeared since 2008. This work is intended to provide the foundation for updating the ascomycete component of the ``Without prejudice list of generic names of Fungi'' published in 2013, which will be developed into a list of protected generic names. This will be subjected to the XIXth International Botanical Congress in Shenzhen in July 2017 agreeing to a modification in the rules relating to protected lists, and scrutiny by procedures determined by the Nomenclature Committee for Fungi (NCF). The previously invalidly published generic names Barriopsis, Collophora (as Collophorina), Cryomyces, Dematiopleospora, Heterospora (as Heterosporicola), Lithophila, Palmomyces (as Palmaria) and Saxomyces are validated, as are two previously invalid family names, Bartaliniaceae and Wiesneriomycetaceae. Four species of Lalaria, which were invalidly published are transferred to Taphrina and validated as new combinations. Catenomycopsis Tibell Constant. is reduced under Chaenothecopsis Vain., while Dichomera Cooke is reduced under Botryosphaeria Ces. De Not. (Art. 59)