Fungal associates of the lodgepole pine beetle, Dendroctonus murrayanae

Abstract

Bark beetles are well known vectors of ophiostomatoid fungi including species of Ophiostoma, Grosmannia and Ceratocystis. In this study, the most common ophiostomatoid fungi associated with the lodgepole pine beetle, Dendroctonus murrayanae, were characterized. Pre-emergent and post-attack adult beetles were collected from lodgepole pines at four sites in British Columbia, Canada. Fungi were isolated from these beetles and identified using a combination of morphology and DNA sequence comparisons of five gene regions. In all four populations, Grosmannia aurea was the most common associate (74-100% of all beetles) followed closely by Ophiostoma abietinum (29-75%). Other fungi isolated, in order of their relative prevalence with individual beetles were an undescribed Leptographium sp. (0-13%), Ophiostoma ips (0-15%), Ophiostoma piliferum (0-11%), a Pesotum sp. (0-11%) and Ophiostoma floccosum (0-1%). Comparisons of the DNA sequences of Leptographium strains isolated in this study, with ex-type isolates of G. aurea, Grosmannia robusta, Leptographium longiclavatum, and Leptographium terebrantis, as well as with sequences from GenBank, revealed a novel lineage within the Grosmannia clavigera complex. This lineage included some of the D. murrayane isolates as well as several isolates from previous studies referred to as L. terebrantis. However, the monophyly of this lineage is not well supported and a more comprehensive study will be needed to resolve its taxonomic status as one or more novel taxa.