Abstract: The relationship of two species of Neonectria associated with beech bark canker in North America was evaluated by comparing isolates of these and additional species of the Neonectria coccinea (Pers.:Fr.) Rossman & Samuels group found on Fagus. Gene regions in the translation elongation factor 1-alpha (EF1-α), RNA polymerase II second largest subunit (RPB2), and β-tubulin were sequenced and analyzed. Results indicate that the fungus associated with beech bark disease previously known as Neonectria coccinea var. faginata Lohman et al. (≍ Nectria coccinea (Pers.:Fr.) Fr. var. faginata Lohman et al.) should be recognized as a separate species, Neonectria faginata, distinct from Neonectria coccinea. Neonectria faginata including its anamorphic state, Cylindrocarpon faginatum C. Booth, is known only on Fagus in North America. A second species associated with beech bark disease in North America is Neonectria ditissima (Tul. & C. Tul.) Samuels & Rossman, which can be distinguished morphologically from Neonectria faginata based on ascospore size, conidial size and shape, and colony pigmentation. Morphological and molecular data indicate that Neonectria ditissima represents an older name for Neonectria galligena Bres. Similarly, the anamorphic state of Neonectria ditissima is the older epithet Cylindrocarpon heteronema with Cylindrocarpon willkommii as a synonym. Neonectria ditissima occurs on a variety of hardwood trees in North America and Europe. Neonectria coccinea occurs only on Fagus in Europe. Neonectria major (Wollenw.) Castl. & Rossman is recognized as a species that occurs only on Alnus in Canada (British Columbia), France, Norway, and the United States (Washington). The following nomenclatural changes are proposed: Neonectria faginata comb. and stat. nov., Neonectria fuckeliana comb. nov., Neonectria hederae comb. nov., Neonectria major comb. and stat. nov., and Neonectria punicea comb. nov.

Key words: beech bark disease, birch bark disease, Cylindrocarpon, hardwood cankers, hardwood diseases, Neonectria.

Resume : Les auteurs ont evalue les relations entre deux especes de Neonectria associees au chancre de l'ecorce du hetre en Amerique du Nord, en comparant deux isolats de ceux-ci ainsi que d'autres especes venant sur Fagus, du groupe Neonectria coccinea (Pers.:Fr.) Rossman & Samuels. Ils ont sequence et analyse les regions genetiques du facteur de traduction de l'elongation 1-alpha (EF1-[alfa]), de la deuxieme plus grande sous-unite de l'ARN polymerase II (RPB2), et de la β-tubuline. Les resultats indiquent que le champignon associe a la maladie de l'ecorce du hetre, connu jusqu'ici comme le Neonectria coccinea var. faginata Lohman et al. ([equivalente a] Nectria coccinea Pers.:Fr.) Fr. var. faginata) devrait faire l'objet d'une espece distincte du Neonectria coccinea, et etre nommee Neonectria faginata. Le Neonectria faginata, incluant son stade anamorphique, le Cylindrocarpon faginatum C. Booth, n'existe que sur les Fagus de l'Amerique du Nord. Une deuxieme espece associee a une maladie de l'ecorce du hetre en Amerique du Nord est le Neonectria ditissima(Tul. & C. Tul.) Samuels & Rossman, qu'on peut distinguer morphologiquement du Neonectria faginata sur la base de la dimension des ascospores, la dimension et la forme des conidies, et la pigmentation des colonies. Les donnees morphologiques et mole culaires indiquent que le Neonectria ditisima est l'ancien nom...