Phylogenetic analyses allow species-level recognition of Leptographium wageneri varieties that cause black stain root disease of conifers in western North America

Daram Choi; Thomas C Harrington; David C Shaw; Jane E Stewart; Ned B Klopfenstein; Duncan R Kroese; Mee-Sook Kim

doi:10.3389/fpls.2023.1286157

Phylogenetic analyses allow species-level recognition of Leptographium wageneri varieties that cause black stain root disease of conifers in western North America

Front Plant Sci. 2023 Dec 22:14:1286157. doi: 10.3389/fpls.2023.1286157. eCollection 2023.

Authors

Daram Choi^{1

2}, Thomas C Harrington³, David C Shaw¹, Jane E Stewart⁴, Ned B Klopfenstein⁵, Duncan R Kroese², Mee-Sook Kim²

Affiliations

¹ Department of Forest Engineering, Resources and Management, Oregon State University, Corvallis, OR, United States.
² Pacific Northwest Research Station, USDA Forest Service, Corvallis, OR, United States.
³ Department of Plant Pathology, Entomology and Microbiology, Iowa State University, Ames, IA, United States.
⁴ Department of Agricultural Biology, Colorado State University, Fort Collins, CO, United States.
⁵ Rocky Mountain Research Station, USDA Forest Service, Moscow, ID, United States.

Abstract

Leptographium wageneri is a native fungal pathogen in western North America that causes black stain root disease (BSRD) of conifers. Three host-specialized varieties of this pathogen were previously described: L. wageneri var. wageneri on pinyon pines (Pinus monophylla and P. edulis); L. wageneri var. ponderosum, primarily on hard pines (e.g., P. ponderosa, P. jeffreyi); and L. wageneri var. pseudotsugae on Douglas-fir (Pseudotsuga menziesii). Morphological, physiological, and ecological differences among the three pathogen varieties have been previously determined; however, DNA-based characterization and analyses are needed to determine the genetic relationships among these varieties. The objective of this study was to use DNA sequences of 10 gene regions to assess phylogenetic relationships among L. wageneri isolates collected from different hosts. The multigene phylogenetic analyses, based on maximum likelihood and Bayesian inference, strongly supported species-level separation of the three L. wageneri varieties. These results, in conjunction with previously established phenotypic differences, support the elevation of L. wageneri var. ponderosum and L. wageneri var. pseudotsugae to the species level as L. ponderosum comb. nov. and L. pseudotsugae comb. nov., respectively, while maintaining L. wageneri var. wageneri as Leptographium wageneri. Characterization of the three Leptographium species, each with distinct host ranges, provides a baseline to further understand the ecological interactions and evolutionary relationships of these forest pathogens, which informs management of black stain root disease.

Keywords: Leptographium; forest pathogen; genetic characterization; phylogeny; taxonomy.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. The project has been supported by USDA Forest Service (FS), State, Private, and Tribal Forestry, Forest Health Protection – Special Technology and Development Program (STDP R5-2020-3) and FS Research & Development Bipartisan Infrastructure Law Ecosystem Restoration Research Project - ERR09.