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

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

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1286157

DOI=10.3389/fpls.2023.1286157

ISSN=1664-462X

ABSTRACT=<p><italic>Leptographium wageneri</italic> 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: <italic>L. wageneri</italic> var. <italic>wageneri</italic> on pinyon pines (<italic>Pinus monophylla</italic> and <italic>P</italic>. <italic>edulis</italic>); <italic>L. wageneri</italic> var. <italic>ponderosum</italic>, primarily on hard pines (e.g., <italic>P</italic>. <italic>ponderosa</italic>, <italic>P</italic>. <italic>jeffreyi</italic>); and <italic>L. wageneri</italic> var. <italic>pseudotsugae</italic> on Douglas-fir (<italic>Pseudotsuga menziesii</italic>). 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 <italic>L. wageneri</italic> isolates collected from different hosts. The multigene phylogenetic analyses, based on maximum likelihood and Bayesian inference, strongly supported species-level separation of the three <italic>L. wageneri</italic> varieties. These results, in conjunction with previously established phenotypic differences, support the elevation of <italic>L. wageneri</italic> var. <italic>ponderosum</italic> and <italic>L. wageneri</italic> var. <italic>pseudotsugae</italic> to the species level as <italic>L</italic>. <italic>ponderosum</italic> comb. nov. and <italic>L</italic>. <italic>pseudotsugae</italic> comb. nov., respectively, while maintaining <italic>L. wageneri</italic> var. <italic>wageneri</italic> as <italic>Leptographium wageneri</italic>. Characterization of the three <italic>Leptographium</italic> 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.</p>