Biodiversity and toxigenicity of Aspergillus section Nigri isolated from different sources in Argentina

GIAJ-MERLERA, G.; BARBERIS, M.; BARBERIS, C.; MAGNOLI, C.; REYNOSO M.M.; TORRES, A.M.

Mendoza

Conferencia; MYCORED ARGENTINA ISM 2011 ConferenceStrategies to reduce the impact of mycotoxins in Latin America in a global context; 2011

UNRC- European Comission Mycored Project- Sociedad Latinoamericana de Micotoxicología

Aspergillus section Nigri is an important group of species in food mycology. They can contaminate agricultural products at different stages including pre-harvest, harvest, processing and handling. These black aspergilli are one of the more difficult groups concerning classification and identification, and several taxonomic schemes have been proposed because the species are occasionally difficult to recognize based solely on their phenotypic characters. The aim of this work was identified the Aspergillus section Nigri species, isolated from different sources, by morphological, physiological and molecular data.Eighty nine strains isolated from peanut, grapes, raisins, beer residues, soybean, coffee and soil, belonging to Aspergillus section Nigri were identified based on phenotypic criteria and divided in subgroups according to macroscopic phenotypic characters. Specific determinations of black Aspergillus species were carried out by the amplification (PCR) using specific primers. From each subgroup strains (11) were randomly selected for the sequencing and analysis of a part of the calmodulin gene. OTA and fumonisin production by the isolates was measured by HPLC. Out of 89 Aspergillus sección Nigri strains, 4 were identified as Aspergillus uniseriate, 21 as A. carbonarius and 64 as A. niger aggregate. The identification of strains based on morphological criteria was confirmed by the molecular technique. All the uniseriate group strains were identified asAspergillus japonicus/aculeatus. Only one strain identified as A. carbonarius did not give any amplification with theCARBO1/CARBO2 primers. This strain was no OTA producer. The analysis of a partial sequence of the calmodulin gene by basic local alignment resulted in a value e = 0.0 and a percentage of 100% identity with a sequence belonging to the strain A. ibericus ITEM 6600. Within the aggregate A. niger were identified molecular species of A. niger /A. awamori, A. tubingensis and A. acidus. A low percentage of A. niger/ A. awamori strains were FB2 producer. The A. niger aggregate is the more frequent group isolated as contaminants from the different sources evaluated. A. carbonarius and Aspergillus uniseriatestrains were isolated only from raisins, peanut and beer residues.The presence of A. niger / awamori fumonisin B2 producer, alert to the possible presence of this toxin in the commodities where this species is a common contaminant. This is the first report of the isolation of A. ibericusoutside Iberian Peninsula.A. ibericus, isolated as a new species from wine grapes and/or dried vine fruit in Portugaland Spain, is closely related to A. carbonarius and unable to produce OTA.