Ambrosiella roeperisp. nov. is the mycangial symbiont of the granulate ambrosia beetle,Xylosandrus crassiusculus

Abstract

Isolations from the granulate ambrosia beetle, Xylosandrus crassiusculus (Coleoptera: Curculionidae: Scolytinae: Xyleborini), collected in Georgia, South Carolina, Missouri and Ohio, yielded an undescribed species of Ambrosiella in thousands of colony-forming units (CFU) per individual female. Partial sequences of ITS and 28S rDNA regions distinguished this species from other Ambrosiella spp., which are asexual symbionts of ambrosia beetles and closely related to Ceratocystis spp. Ambrosiella roeperi sp. nov. produces sporodochia of branching conidiophores with disarticulating swollen cells, and the branches are terminated by thick-walled aleurioconidia, similar to the conidiophores and aleurioconidia of A. xylebori, which is the mycangial symbiont of a related ambrosia beetle, X. compactus. Microscopic examinations found homogeneous masses of arthrospore-like cells growing in the mycangium of X. crassiusculus, without evidence of other microbial growth. Using fungal-specific primers, only the ITS rDNA region of A. roeperi was amplified and sequenced from DNA extractions of mycangial contents, suggesting that it is the primary or only mycangial symbiont of this beetle in USA.

First report of a sexual state in an ambrosia fungus:Ambrosiella cleistominutasp. nov. associated with the ambrosia beetleAnisandrus maiche

“…Ambrosiella cleistominuta was the only ambrosia fungus isolated from the mycangium of An. maiche, supporting the conclusion that Ambrosiella is tightly associated with Xyleborini species with mesonotal pouch mycangia (Harrington et al 2014;Mayers et al 2015). Surprisingly, A. cleistominuta produced ascomata in cultures and in galleries.…”

“…1h, i), similar in appearance to that of other Ambrosiella (Francke-Grosmann 1956; Kaneko & Takagi 1966;Harrington et al 2014, Mayers et al 2015. The propagules appeared to proliferate by schizogenous, arthrospore-like growth.…”

“…The prominent dual lobes described for the mycangia of related genera, such as Cnestus, Eccoptopterus, and Xylosandrus (Stone et al 2007;Harrington et al 2014;Mayers et al 2015), were not observed in the An. maiche mycangia.…”

“…dispar, the mycangium of An. maiche is relatively small and lacks the dual lobes reported for Cnestus, Eccoptopterus, and Xylosandrus Francke-Grosmann 1967;Stone et al 2007;Harrington et al 2014;Mayers et al 2015) The conspicuous pits on the dorsal side of the scutellum are ornamented with setae on their rims, which sometimes hold fungal spores. Stone et al (2007) of these pits and setae is unclear.…”

“…Like A. grosmanniae, only produce aleurioconidiophores (Harrington et al 2014;Mayers et al 2015). Females of Xylosandrus have been reported to evert their large, lobed mycangia to acquire aleurioconidia from the ambrosia growth along the gallery walls (Kaneko 1967), and these species may not need phialoconidiophores for sowing of their mycangia.…”