Undifilum, a new genus for endophytic Embellisia oxytropis and parasitic Helminthosporium bornmuelleri on legumes

Fungal endophytes of Oxytropis kansuensis Bunge from China, previously described as Embellisia oxytropis Q. Wang, Nagao & Kakish, and endophytes of Oxytropis sericea Nutt. and Oxytropis lambertii Pursh from the United States were compared and are reported here as conspecific members of a new genus in the Pleosporaceae, Undifilum, based on morphological and molecular analyses. Morphological comparisons revealed characters that are similar to those of the genus Embellisia including conidia ovate to obclavate to long ellipsoid, straight or slightly to decidedly inequilateral with occasionally one or two cells distinctly swollen, and transepta occasionally thickened, dark, and rigid in comparison with the exterior conidium wall. However, upon germination, conidia produced unique and diagnostic germ tubes that were wavy or undulating in their growth until branching. Moreover, all isolates were found to produce the toxic alkaloid swainsonine. Parsimony analysis of sequences from ITS1-5.8S-ITS2, glyceraldehyde-3-phosphate dehydrogenase gene, and mitochondrial small subunit rDNA data sets revealed that the Oxytropis endophytes formed a clade distinct from other Embellisia species and species in the genera Alternaria, Ulocladium, Nimbya, and Crivellia. A second taxon, Helmintho- sporium bornmuelleri P. Magnus, was reexamined and found to possess similar morphological features to those of the Oxytropis isolates, but lacked swainsonine production. Sequence analysis placed this second taxon in the same clade with high bootstrap support. The distinct morphology and genetics of these taxa demonstrates that these fungi, both recovered from legumes, represent a new genus, hereinafter described as Undifilum. The two species now placed in this genus are redescribed as Undifilium oxytropis and Undifilium bornmuelleri. Resume´ : Les auteurs ont compareles endophytes fongiques de l'Oxytropis kansuensis Bunge de Chine prealablement de ´- crits comme Embellisia axytropis Q. Wang, Nagao & Kakish, et les endophytes de l'Oxytropis sericea Nutt. et de l'Oxy- tropis lambertii Pursh des Etats-Unis; on en fait des membres conspecifiques le nouveau genre Undifilum membre des Pleosporaceae, basesur des analyses morphologiques et moleculaires. Les comparaisons morphologiques revelent des car- acteres similaires aceux du genre Embellisia, incluant des conidies ovees aobclavees ou ellipsoo¨des, droites ou legerement anettement inequilaterales, avec occasionnellement une ou deux cellules distinctes et enflees, munies de transepts occa- sionnellement epais, sombres, et rigides comparativement ala paroi externe des conidies. Cependant, en cours de germina- tion, les conidies produisent des tubes germinatifs uniques et caracteristiques d'aspect sinueux ou acroissance ondulee jusqu'aleur ramification. De plus, on constate que tous les isolats produisent de la swainsonine, un alcaloo¨de toxique. Les analyses en parcimonie des ITS1-5.8S-ITS2, du gene de la deshydrogenase du glyceraldehyde-3-phosphate, et les donnees de la petite sous unitede l'ADN mitochondrial montrent que les endophytes des Oxytropis forment un clade distinct differ- ent des autres especes d'Embellisia ainsi que les especes des genres Alternaria, Ulocladium, Nimbya et Crivellia. Les au- teurs ont reexamineun second taxons, l'Helminthosporium bornmuelleri P. Magnus et ont constatequ'il possede des caracteristiques morphologiques similaires a celles des isolats des Oxytropis, mais ne produit pas de swainsonine. Les anal- yses de sequences situent ce deuxieme taxon dans le meme clade avec un fort support bootstrap. La morphologie et la ge ´- netique distinctes de ce taxon demontrent que ces champignons, tous deux obtenus de legumineuses, representent un nouveau genre, ici decrit comme Undifilum. Les auteurs redecrivent les deux especes maintenant attribuees a ce genre