Morphotypic and molecular identification of filamentous fungi from Spanish blue-veined Cabrales cheese, and typing of Penicillium roqueforti and Geotrichum candidum isolates

Abstract

Thirty five white and blue-greenish filamentous fungi, dominant during ripening of Cabrales cheese, were morphotypically and genotypically identified. Morphotypic analysis identified Penicillium spp. (12 isolates), Penicillium roqueforti (11 isolates), Geotrichum candidum (10 isolates), Acremonium charticola (1 isolate), and one isolate that could not be identified. Polymerase chain reaction (PCR) amplicons of their ITS1-5.8S-ITS2 region were subjected to Restriction fragment length polymorphism (RFLP) analysis with six restriction enzymes. Strains morphotypically identified as P. roqueforti all showed identical RFLP profiles with all enzymes, as did all the G. candidum strains; confirming their phenotypic classification. However, molecular analysis showed the Penicillium spp. group to be composed of P. commune (5 isolates) , P. chrysogenum (4 isolates), P. roqueforti (2 isolates), and P. citreonigrum (1 isolate). The genetic diversity found among the different P. roqueforti and G. candidum isolates was assessed by Rapid amplified polymeric DNA-polymerase chain reaction (RAPD-PCR) with two primers. Nine P. roqueforti strains were defined among the 13 isolates, and every G. candidum isolate represented an individual strain.