Digestion of DNA regions to discriminate ochratoxigenic and non-ochratoxigenic strains in the Aspergillus niger aggregate.

Aspergillus strains belonging to the Aspergillus niger aggregate, either isolated from Italian grapes or received from public collections, were analysed in order to discriminate between the ochratoxin A (OTA) producing and the non-producing strains by means of the analysis of Internal Transcribed Spacers (ITS), Intergenic Spacers (IGS) and of a beta-tubulin gene portion. A. niger and Aspergillus awamori were identified observing the macro- and microscopic features of the colonies and the strains ochratoxigenicity was evaluated through Thin Layer Chromatography and/or High Performance Liquid Chromatography. PCR amplification of ITS, IGS and beta-tubulin gene portion produced 600, 440 and 550 bp amplicons, respectively, in all the analysed strains. The digestion of the IGS amplicon with Hinf I and of the other two amplicons with Rsa I, revealed one main profile type ("T-C-C") associated with the A. niger aggregate strains which lack the ability to produce OTA.