Species-level recognition of the three varieties of Leptographium wageneri (cause of black stain root disease) and prediction of their potential suitable climate spaces in the western USA

Abstract

Black stain root disease (BSRD), a vascular wilt disease of conifers caused by a native insect-vectored fungus, is among the top five most damaging root diseases in forests of the western United States (Hadfield et al., 1986). Previously, the fungi that cause BSRD were described as three varieties of Leptographium wageneri - L. wageneri var. wageneri, L. wageneri var. ponderosum, and L. wageneri var. pseudotsugae (Kendrick) Wingfield (Kendrick, 1962; Wingfield, 1985). These L. wageneri varieties were differentiated based on morphology, physiology (Harrington and Cobb, 1987), and ecology including host associations, as follows: 1) L. wageneri var. wageneri on single-leaf pinyon (Pinus monophylla) and pinyon pine (P. edulis), 2) L. wageneri var. ponderosum on Jeffrey pine (P. jeffreyi) and ponderosa pine (P. ponderosa), and 3) L. wageneri var. pseudotsugae on Douglas-fir (Pseudotsuga menziesii) (Harrington and Cobb, 1984, 1986; Hessburg et al., 1995) (Figure 1). The three pathogens were originally classified as different varieties because their distinguishing characteristics were regarded as relatively minor and early DNA-based characterizations were not definitive, but robust phylogenetic analyses can provide the basis for species-level recognition of the L. wageneri varieties (Choi et al., 2023). In addition, bioclimatic models may be useful for predicting the suitable climate space (potential distribution) and adaptability for each BSRD pathogen in western North America under the contemporary and projected future climates.

Citation

Choi, Daram; Harrington, Thomas C.; Shaw, David C.; Stewart, Jane E.; Bennett, Patrick I.; Klopfenstein, Ned B.; Kroese, Duncan R.; Kim, Mee-Sook. 2024. Species-level recognition of the three varieties of Leptographium wageneri (cause of black stain root disease) and prediction of their potential suitable climate spaces in the western USA. In: Brooks, Rachel K., compiler. Proceedings of the 68th Western International Forest Disease Work Conference; 5-9 June 2023; Rohnert Park, CA. Online: https://www.wifdwc.org. p. 90-93.