Two new Leptographium spp. reveal an emerging complex of hardwood-infecting species in the Ophiostomatales

Abstract

Species of Leptographium are generally characterized by mononematous conidiophores and are commonly associated with bark beetles and weevils. These species are responsible for sapstain and in some cases serious diseases on a range of primarily coniferous trees. In comparison with coniferous trees, the occurrence of Leptographium species on hardwood trees has been poorly studied in Europe. During a survey of ophiostomatoid fungi on various tree species in Norway and Poland, three unusual species, which fit the broader morphological description of Leptographium spp., were found in association with Scolytus ratzeburgi, Dryocoetes alni and Trypodendron domesticum on a variety of hardwoods, and from wounds on Tilia cordata. Phylogenetic analyses of sequence data for three gene regions (ITS2-LSU, β-tubulin, and TEF1-α) showed that these Leptographium species are phylogenetically closely related to each other and form a well-supported lineage that included Grosmannia grandifoliae and Leptographium pruni. The first species could be distinguished from the other Leptographium species based on conidiophores arising from spiral hyphae, chlamydospore-like structures and a hyalorhinocladiella-like synanamorph in culture. The second species differs from the previous one by having distinctly shorter conidiophores and smaller conidia. This species also produces a well-developed sporothrix-like synanamorph with denticulate conidiogenous cells. Based on these unusual morphological characteristics and distinct DNA sequences, these fungi were recognised as new taxa for which the names Leptographium trypodendri sp. nov. and L. betulae sp. nov. are provided. The third group of isolates belonged to Grosmannia grandifoliae, representing the first report of this species outside of the USA. The newly defined G. grandifoliae complex is the first species complex in Leptographium s.l. consisting of only hardwood-infecting species.

Two new species of Ophiostomatales (Sordariomycetes) associated with the bark beetle Dryocoetes alni from Poland

“…The species were named Ceratocystiopsis synnemata and Leptographium alneum. The results confirm earlier findings that many species of the Ophiostomatales are associated with hardwoodinfesting bark beetles in Poland (Jankowiak et al 2017(Jankowiak et al , 2018(Jankowiak et al , 2019aAas et al 2018).…”

“…However, the results of the present study confirm previous Polish investigations that some of the Leptographium species have a close affinity to hardwoods in Europe. Recently, L. betulae, L. tardum, and L. trypodendri were collected from hardwood-infesting bark beetles in Poland (Jankowiak et al 2017(Jankowiak et al , 2018, while three other Leptographium species have been isolated and formally described from hardwood wounds (Jankowiak et al 2018(Jankowiak et al , 2019c.…”

“…Two new species were described. Ophiostomatoid fungi on hardwoods have been relatively well investigated in Poland (Jankowiak et al 2017(Jankowiak et al , 2018(Jankowiak et al , 2019aAas et al 2018), but in other parts of Europe they are still poorly studied. In addition, many ophiostomatoid species have not been formally described and our study has contributed to filling this knowledge gap.…”

“…Leptographium sensu lato is a broadly defined polyphyletic group of morphologically similar species (De Beer and Wingfield 2013). To date, Leptographium sensu lato includes ten species complexes and some smaller lineages with uncertain taxonomic positions (De Beer and Wingfield 2013;Jankowiak et al 2017). The genus Leptographium contains more than 150 described taxa, most of which are associated with phloem-and wood breeding beetles that affect a wide range of plants worldwide (Jacobs and Wingfield 2001).…”

Three new Leptographium spp. (Ophiostomatales) infecting hardwood trees in Norway and Poland

“…was for a long time the only Leptographium/Grosmannia species reported from hardwoods (Davidson 1971 ; Jacobs and Wingfield 2001 ). Our recent research (Jankowiak et al 2017 ) expanded the knowledge of hardwood-infecting Leptographium spp. in Europe by describing two new species of Leptographium that were assigned to the newly defined Grosmannia grandifoliae species complex.…”