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Abstract
A sclerotium-forming member of Aspergillus section Nigri was sampled from a population in a single field in North Carolina, USA, and identified as A. tubingensis based on genealogical concordance analysis. Aspergillus tubingensis was shown to be heterothallic, with individual strains containing either a MAT1-1 or MAT1-2 mating-type gene. Strains of opposite mating type were crossed on mixed cereal agar and incubated for 5–6 months. Stromata typically formed 1–2 indehiscent ascocarps containing asci and ascospores within the pseudo-parenchymatous matrix in a manner similar to the Petromyces sexual stage from section Flavi, which is closely related to section Nigri. Ascospores of A. tubingensis differed from those of section Flavi species in the reticulate ornamentation of ascospores and the presence of two crests that form an equatorial furrow. Sexual reproduction in A. tubingensis may be useful for enhancing enzyme and organic acid production through recombination-mediated genetic engineering of industrial strains.
Acknowledgments
Appreciation is given to Travis Walk and Amy McGovern for technical assistance and to Valerie K. Lapham at the Center for Electron Microscopy (NC State University) for assistance with the SEM.
This work was supported in part by the North Carolina Cooperative State Research, Education and Extension Service 2008-34500-19396 and by the National Research Initiative of the USDA Cooperative State Research, Education and Extension Service, Grant No. 2005-35319-16126 to I. Carbone. R. A. Olarte was supported by a USDA-NIFA Pre-Doctoral Fellowship.