Biocontrol potential of Aspergillus section Nigri strains against Aspergillus carbonarius

Aspergillus carbonarius is the main producer of ochratoxin A (OTA) in grape and grape products. Good agricultural practices and preventive measures such as the use of biological control agents are key to decreasing OTA concentration in the final product. This study evaluated non-ochratoxigenic strains from Aspergillus section Nigri isolated from grape environments for their ability to control OTA production. In vitro interactions between an ochratoxigenic strain of A. carbonarius and 22 non-ochratoxigenic strains were evaluated using microtiter plates. Biocontrol potential was determined by measuring OTA reduction, while competitiveness was quantified through a specific qPCR assay. Results showed that both OTA reduction and competitive ability were strain-dependent. Co-inoculation experiments revealed that most non-OTA-producing strains reduced OTA levels, with Aspergillus uvarum showing the strongest inhibition. Aspergillus japonicus and Aspergillus trinidadensis also reduced OTA, whereas biseriate species such as Aspergillus niger, Aspergillus welwitschiae, and Aspergillus brasiliensis had minimal impact. The qPCR competitiveness assays revealed that A. carbonarius typically dominated mixed cultures, except when co-cultured with highly competitive A. uvarum strains. Notably, strain A-6760 reduced A. carbonarius abundance to below 6%. This strong competitiveness aligned with significant OTA suppression, suggesting competitive exclusion as the main biocontrol mechanism. Overall, the developed qPCR assay provides a rapid, precise method for fungal interaction evaluation. A. uvarum strains showed great promise for mitigating OTA contamination in grapes and wine through its combined dominance and toxin reduction capacity. Future research should evaluate their effectiveness under field conditions. KEY POINTS: • Atoxigenic black aspergilli were tested as biocontrol agents vs. A. carbonarius. • Competitiveness and OTA reduction varied by strain; uniseriates performed best. • A. uvarum A-6760 shows promise as a biocontrol agent to reduce OTA in grapes.