Specific PCR primers for the detection of isolates of Aspergillus carbonarius producing ochratoxin A on grapevine

Abstract

Aspergillus carbonarius is the main fungus responsible for ochratoxin A (OTA) production on grapes and in wine. Fungal polyketide synthases are involved in OTA biosynthesis in Aspergillus species. The ketosynthase (KS) domain of an A. carbonarius gene encoding polyketide synthase (pks) was isolated, cloned and sequenced. The nucleotide sequence showed high similarity to KS domains isolated from other Aspergillus species. The sequence was used to design a new set of primers in order to identify potential producers of OTA from among isolates of A. carbonarius. The primers amplified all the A. carbonarius strains tested specifically, and did not amplify any other species of Aspergillus or Penicillium normally found on grapes or involved in OTA biosynthesis. Further, gene expression was related to OTA production. Both gene transcription and levels of the mycotoxin were higher when A. carbonarius was grown on YES medium at 15°C and 30°C, whereas a low transcription and mycotoxin presence were observed when the fungus was grown on PDB medium at the same temperatures. No transcription or OTA production were observed when the fungus was grown on either YES or PDB at 10°C. The primers will be useful for the detection of ochratoxigenic strains of A. carbonarius both in vineyards and during wine production.