Ochratoxigenic capacity of Black Aspergillus isolated of soil of vineyards of different regions from Argentina

GIAJ-MERLERA G, ; BARBERIS, M.; REYNOSO MM; CHULZE SN; TORRES AM

Carlos Paz

Congreso; VI Congreso Argentino de Microbiologia General; 2009

Sociedad Argentina de Microbiología General (SAMIGE)

The different ochratoxigenic A (OTA) producing species lives as saprophytes in the superficial cap of the vineyard soil with is the major inoculum source of Aspergillus section Nigri. There has been postulated that the movement of the air deposits the spores from the soil in the grape surface, thus the risk of contamination with OTA in wines might br related to the presence of toxigenis strains in the soil. The aim of this work was to evaluate the frequency of contamination whit OTA-producers species in vinwyard soils from different wine.producers regions of Argentina for classic and molecular methodogy; and to determine the toxigenic capacity of the strains isolated by thin layer chromatography (TLC). The sampling was done in the wine-producer regions of Mendoza, San Juan, Neuquén, Río Negro and La Rioja, during the harvest season 2008. We determinated the total fungal and Aspergillus section Nigri count using surface spreading in the media dichloro rose bengal chloramphenicol (DRBC). The strains belonging to the genera Aspergillus section Nigri isolated were subcultured on agar malt extract, for identification by classical methods, and Czapek yeast extract agar, for subsequent toxin extraction and quantification by TLC. The strains were identified by molecular methods based on PCR. Vineyards with higt incidence of Aspergillus section Nigri were founded by Rio Negro province (General Enrique Godoy and General Roca) with levels of 2.9x104 and 2.3x104 cfu/g, respectively; while the other locations ranged from 9.1x102 and 4.8x103 cfu/g (mean= 2.8x103). From a total of 147 strains isolated belonging to Aspergillus section Nigri, 61 were classified as black Aspergillus uniseriated and 81 as biseriated, of which 5 were A. carbonarius. Conditions were optimized for PCR amplification for each pair of primers which resulted in the identification of firtt Aspergillus black uniseriate (A. aculeatus/A. japonicus), Aspergillus black biseriate (A. niger, A. tubigensis) and A. carbonarius. Concluions: -All soil samples analyzed were contaminated with Aspergillus section Nigri; - The biserited species were isolated in higher frequency; - The main ochratoxigenic species A. carbonarius was isolated with low-frequency. –Those black Aspergillus strains not presenting a distinctive morphological characteristics to be classified by classical taxonomy were possible to identified using PCR with specif promers; -In genral, all the strains isolated demostrated low capacity to produce OTA