Submitted to: Persoonia: Molecular Phylogeny and Evolution of Fungi
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/10/2012
Publication Date: 12/29/2012
Citation: Minnis, A.M., Rossman, A.Y., Kleczewski, N.M., Flory, L.S. 2012. Bipolaris microstegii Minnis, Rossman, Kleczewki & S.L. Flory, sp. nov. Persoonia: Molecular Phylogeny and Evolution of Fungi. 29:150-151. Interpretive Summary: Invasive weeds can be controlled without the use of harmful chemicals using plant pathogenic fungi. In searching for fungi to control Japanese stiltgrass, an invasive weed from Asia, a fungus was found that kills this weed. However, this fungus has never been seen before, thus it must be named, described thoroughly, and compared with other known fungi. In this paper the new fungal species is named after the host plant and described the way it appears both on the plant and growing on agar plates in the laboratory. In addition portions of the DNA of the fungus were sequenced and compared with other similar fungi. All these methods were used to determine that this fungus was not previously known and to provide a name and the ability for others to identify it. Using the named fungus plant pathologists and conservation biologists can conduct the research to determine if this fungus will be useful and safe to apply in the field for the control of Japanese stiltgrass.
Technical Abstract: Many species of Bipolaris are significant pathogens of grasses. A new species of Bipolaris was isolated from Microstegium vimineum, an invasive plant in the USA. The fungus causes disease on Microstegium, but it also infects a wider range of hosts. Comparison of ITS and gpd sequence data to sequences in GenBank and subsequent phylogenetic analyses based on Group 1 species, referred to as Bipolaris, suggest that the present species is distinct and closely related to B. victoriae and B. zeicola. These species of Bipolaris consist of a highly pathogenic species complex that shows large differences in pathogenicity and host ranges in spite of few genetic differences in the sequenced loci. Bipolaris microstegii is morphologically similar to B. miyakei and B. zeicola. A probable original culture of B. miyakei (CBS 197.29) is not closely related to B. microstegii based on ITS and gpd sequences. Bipolaris microstegii differs from B. zeicola by its longer and sometimes branched conidiophores. The host, Microstegium vimineum, is native to Asia. Several isolates of Bipolaris are known from Microstegium in Asia, but the origin of B. microstegii is unknown. The leaf spots on Microstegium are up to ca. 2 cm × 0.5 cm, ellipsoid to irregular, brown with a darker, near black border. The conidiophores are macronematous, mononematous, erect, more or less straight to slightly flexuous, simple or with a single dichotomous branch, cylindrical, geniculate at apex, pale brown to medium brown, often darker towards apices, walls smooth, septate, up to at least 750 µm long × 5–8 µm in diam. The conidiogenous cells are integrated, terminal, with sympodial proliferation and darkened, circular scars. The conidia are solitary, curved, cylindrical, to obclavate, apex obtuse, base obtuse with inconspicuous hilum, pale brown becoming medium to dark brown, end cells usually paler, walls smooth or somewhat grainy in appearance, 5–10 distoseptate with septa becoming accentuated at maturity, 40–97.5–(105) × 12.5–15–(17.5) µm.