Genetic variability within the Aspergillus viridinutans species

The intraspecific variability of the Aspergillus viridinutans species was e xamined using various techniques including morphological examinations, carb on-source-utilization tests, restriction-enzyme analysis of the mitochondri al and nuclear DNA, and sequence analysis of part of the beta -tubulin gene . Although the genetic distances between the isolates were higher than betw een, e.g., A. fumigatus and Neosartorya fische ri, most A. viridinutans iso lates, together with N. aureola and N. udagawae strains, were found to belo ng to a single cluster based on sequence data. Strain FRR 1266, which was e arlier classified as a highly divergent A. fumigatus isolate, was found to belong to the A. viridinutans species. The ochratoxin A producing A. viridi nutans strain IMI 306135 was most closely related to an asexual isolate. Th ese two latter strains were more closely related to A. fumigatus and N. fis cheri than to any A. viridinutans strains, and possibly represent a new spe cies in the Aspergillus section Fumigati. The dendrogram based on carbon so urce utilization data and results of restriction analysis of the mitochondr ial and nuclear DNA of the strains supported most of the evolutionary relat ionships observed on the basis of sequence data. The results indicate that the presence or absence of nodding conidial heads is not an unequivocal mor phological character for the identification of species within the Aspergill us section Fumigati.