Characterization of non aflatoxigenic Aspergillus flavus strains for biological control of aflatoxins in Argentina

ALANIZ ZANON M.S; BARROS, G.G; CHULZE, S.N

Ottawa

Congreso; Mycored-North America; 2012

Univeridad de Carleston ISM

Biocontrol by competitive exclusion has been developed as one of the promising strategy of controlling aflatoxin in different crops. This technology involves the use of atoxigenic isolates of Aspergillus flavus to competitively exclude aflatoxin producers and alter the composition of fungal communities associated with crops. The aims of this study were: (i) to characterize non-aflatoxigenic Aspergillus flavus strains in relation to aflatoxin and cyclopiazonic acid (CPA) production, and sclerotia morphotype;(ii) to determine the presence/absence of four DNA fragments specific for aflR, nor-1, ver-1, and omt-A genes from the aflatoxin gene cluster. Aflatoxins and CPA production was evaluated according to Horn et al. (1996), sclerotia production according  to Cotty (1989) and the evaluation of genes by using a multiplex PCR-system proposed by Criseo et al. (2008). From 102 strains evaluated, 50 were non-aflatoxigenic and only 13 A. flavus strains (26%) did not produce aflatoxins neither CPA. Most strains tested were characterized as L phenotype as produced few sclerotia with average diameter >400 mm. Differences among the non-aflatoxigenic A. flavus strains was observed in the presence/absence of the PCR products of the genes from the biosynthetic cluster, being the nor-1 gene the most representative between the four aflatoxin structural assayed genes. Several atoxigenic strains showed DNA fragments that correspond to the complete set of genes. These results indicate that other genes need to be analyzed to have a better characterization of the strains at molecular level. The present study shows that some non-aflatoxigenic A. flavus strains are good candidate for using as biocontrol agentsby competitive exclusion.