Molecular strategy to discriminate between two ochratoxin A producing Aspergillus niger aggregate species isolated from fresh and dried grapes
Sabeh Melki Ben Fredj, Angélique Gautier, Yves Brygoo and Ahmed Mliki
Annals of Microbiology, 59, Number 3, 635-641, 2009
2009
บทคัดย่อ
Aspergillusgenus is an ubiquitous fungal group that colonizes a wide range of substrates. A total of 100 Tunisian fungal strains isolated at harvest time from fresh and dried grapes were identified within the sectionNigri and tested for their ochratoxin A (OTA) producing abilities. Of the isolates, 45% were identified asAspergillus tubingensis, 34% asAspergillus niger, 12% asAspergillus japonicus and 9% asAspergillus carbonarius. The OTA production was assessed using Czapeck yeast extract agar which revealed that 25% of the isolates belonging to theAspergillus niger aggregate were OTA producers, while 97% were identified as belonging to theA. Carbonarius species. To distinguish betweenA. Niger andA. Tubingensis, PCR was used to amplify the ITS-5.8S rDNA for these two strains. The sequence analysis of the PCR products revealed a full similarity between the two species. Thus, a new molecular strategy has been developed based on the targeting of the gene from nitrate reductase (niiA) and nitrite reductase gene (niaD), as well as the intergenic region of the gene (niiA-niaD). The subsequent screening revealed that two new specific primer pairs can be used to identify specificallyA. Niger andA. Tubingensis.