Soil populations of Aspergillus section Flavi from the main and new peanut growing areas in Argentina

ORTIZ M.P.; BARROS G.G.; REYNOSO M.M.; TORRES A.M.; CHULZE, S.N; RAMIREZ M.L.

Mendoza

Conferencia; ISM Conference 2011 “Strategies to reduce the impact of mycotoxins in Latin America in a global context; 2011

ISM, UNRC, MYCORED

The aims of this study were to extend the knowledge of Aspergillus section Flavi populations isolated from soil samples collected in the new peanut growing areas in Argentina and to compare these populations with populations isolated from the major peanut  growing area. Soil samples were collected from Formosa and South of Cordoba Province during the harvest season 2008. Total mycoflora  and  Aspergillus section Flavi was done by surface spread method on DRBC and DG18 media. The isolates belonging to Aspergillus section Flavi were identified by macroscopic and microscopic characteristics, sclerotia production, aflatoxins and cyclopiazonic acid production was evaluated. The data showed that the total mycoflora count was higher and the incidence of Aspergillus section Flavi was lower in samples collected from the new peanut cultivation areas in comparison with the levels found in soil samples collected in the main peanut growing area.  The mean values of total mycoflora and Aspergillus section Flavi were 3.6 x 104 and 319 ufc/g respectively. Out of 335 strains isolated withing the Aspergillus section Flavi 90 % were A. flavus, 6 % Aspergillus parasiticus and 4 % were not able to identified using morphological markers. Among the A. flavus isolated 87 % were L strains and 3% wre S strains. A 67% of A. flavus were AFB producers and 81 % were cyclopiazonic acid producers. There were not significant differences in the mean level of AFB1 production among strains isolated from the different areas with no history of peanut cultivation. The levels of toxin produced were lower that those produced by strains isolated from areas with long term of peanut cultivation. Principal component analysis showed that fields with recent history of peanut cultivation are closely related with the isolates belonging to A. flavus, producers of low aflatoxin levels, while typical groundnut regions are closely related with high percentages of A. parasiticus and A. flavus S phenotype, producers of higher  aflatoxin levels .