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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.
Acknowledgments
The technical assistance of Ruben Garcia, Rodrigo de Freitas, Joseph Steimel and Susan Best is greatly appreciated. Doug le Doux (Missouri Department of Agriculture) provided beetles preserved in ethanol and Dan Miller (US Forest Service, Athens, Georgia) graciously identified ambrosia beetles from Georgia. Chase Mayers was supported in part by a fellowship from the Office of Biotechnology, Iowa State University (ISU). Other financial support was provided by the US Forest Service through a cooperative agreement with ISU and by award No. 2009-51181-05915 from the USDA-CREES Specialty Crop Research Initiative.