Characterization of Aspergillus section Flavi in soils from new peanut growing areas of Argentina

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

Freising

Workshop; ICFM workshop: Food Mycology in a Globalized World – Challenges and Solutions to the Safety of Food; 2013

International Commission in Food Mycology

Peanuts is an economically important crop in Argentina, with Cordoba Province (main growing peanut region) accounting for approximately 98% of the total production. Diverse factors such as soil fungal pathogens, climatic conditions and soil degradation can explain the exploration of new growing areas in others provinces or in marginal areas of the main peanut growing region. The aim of the present study were to extend the knowledge of the biodiversity of Aspergillus section Flavi soil populations from new peanuts growing areas and to compare these populations with population isolated from the traditional peanuts growing region. Soil samples were collected from Formosa Province, La Pampa Province and south of Cordoba Province during 2008 harvest season. Total mycobiota and Aspergillus section Flavi was done by surface spread method on DRBC and DG18 media. Four hundred and thirty isolates belonging to Aspergillus section Flavi were characterized by morphology, sclerotia production and mycotoxin production (aflatoxin and ciclopiazonic acid production). The mean values of total mycobiota and Aspergillus section Flavi were 3.6 x 104 and 319 ufc/g respectively. Out of 430 strains isolated within the Aspergillus section Flavi 90 % were identified as A. flavus, 6 % as A. parasiticus and 4 % were not able to be identified using morphological markers. These strains were further identified using calmoduline gene sequence as A. caelatus. Among the A. flavus isolated 88 % were L strains, 3% were S strains and 10 % were not able to produce sclerotia. Seventy one percent of A. flavus were aflatoxin producers and 81 % were cyclopiazonic acid producers. A relative large proportion of A. flavus strains (n= 111, 29 %) isolates were not able to produce aflatoxin. Molecular analysis of omt-A, ver-1, nor-1 and afl-R genes involve on aflatoxin biosynthesis pathway of 34 strain of A. flavus non aflatoxigenic showed that 19 strains have absence of 1, 2 or 3 of the genes analyzed. Just 1 strain showed absence of the 4 genes studied. There were not significant differences in the mean level of AFB1 production among strains isolated from the different new areas of peanut cultivation. The levels of toxin produced were lower than those produced by strains isolated from areas with long term history 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 L phenotype, 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.