Factors affecting distribution and abundance of Aspergillus section Nigri in vineyard soils from grapevine growing regions of Argentina

Abstract

Background: Aspergillus species belonging to section Nigri are the main fungi responsible for ochratoxin (OTA) contamination in grapes and wine. These species live as saprophytes in the superficial layer of the vineyard soil. We evaluated the biodiversity of potentially ochratoxigenic strains of Aspergillus section Nigri isolated from vineyard soils from different grapevine growing regions of Argentina. The isolates were characterized by classical and molecular methods. A multiple correspondence analysis wasperformedto identify theoverall correlation of the Aspergillus groupdistributionwith environmental conditions, geographical characteristics and vineyard practices. Results; Aspergillus niger aggregate was the prevalent group (71%) and A. carbonarius made up only 2%. Species discrimination by species-specific primers showed that in A. niger aggregate 89% were A. tubingensis; 97% of the uniseriate were A. japonicus/A. aculeatus. Isolates belonging to these groupswere unable to produceOTA.Our results clearly demonstrate a strong association between presence of A. carbonarius, high average temperatures and drip irrigation. Precipitation levels appear as a secondary factor, and altitude, vineyard age, predominant species, grape variety or total fungal count showed no association with A. carbonarius. Conclusion: We demonstrated a low prevalence of ochratoxigenic species in vineyard soil fromthe grape-growing regions of Argentina.