New species, combinations and records of Thyronectria, with a key to species

The new species Thyronectria ulmi is described from Ulmus laevis and U. minor collected in Austria, the Czech Republic and Slovakia. It is morphologically and phylogenetically close to the North American T. chrysogramma, which also occurs on Ulmus and shares olive green to brown muriform ascospores, but differs from the latter by geographic distribution, narrower asci, smaller ascospores with fewer septa and DNA sequence data from seven loci (ITS and LSU regions of nu rDNA, ACT1, RPB1, RPB2, TEF1 and TUB2 genes). As in many other Thyronectria species, ascomata of T. ulmi were closely associated with Diplodia, indicating a fungicolous habit. The genus Neothyronectria is synonymised with Thyronectria based on morphological and molecular phylogenetic data, and the new combinations T. citri and T. sophorae are proposed. A key to 45 accepted species of Thyronectria is provided. The recently described T. abieticola, previously known from the Czech Republic and France, is newly reported from Austria and Slovakia; its pycnidial anamorph is recorded, described and illustrated from natural substrates for the first time. A sporodochial anamorph is reported from natural substrates for T. aurigera, a new record for Austria as well. New host and distribution records include T. rhodochlora on Acer pseudoplatanus in Austria and Fraxinus excelsior in the Czech Republic, T. sinopica on Hedera colchica in the Czech Republic and Bupleurum fruticosum in Spain, and T. zanthoxyli on Sorbus aucuparia in Belgium and Ulmus sp. in the USA. Thyronectria cucurbitula is confirmed by sequence data from Pinus strobus collected in the Czech Republic, challenging the host ranges given for T. cucurbitula (Pinus subgen. Pinus) and T. strobi (Pinus subgen. Strobus), and questioning the European and Chinese records of T. strobi.