SSR analysis and competition assay in peanut and maize using non-aflatoxigenic Aspergillus flavus strains in Argentina

ALANIZ ZANON M.S.; BARROS, G.; COTTY, P.; CHULZE, S.

Conferencia; International Mycotoxin Conference; 2014

Biological control based on competitive exclusion has been developed as one of the most promising strategies for management of aflatoxins in several crops including peanuts (Arachis hypogaea L.) and maize (Zea mays). This type of biocontrol involves applying one or more non-toxigenic Aspergillus flavus isolate to developing crops in order to competitively exclude aflatoxin producers. In so doing, this technique modifies the fungal communities associated to crops and increases crop safety.  The general aim of the present work was selection of non-aflatoxigenic A. flavus isolates that have potential for biocontrol from 47 isolates previously characterized with morphological, physiological, molecular and genetic parameters. The characterized fungi were isolated from several agricultural regions of Córdoba province. The work also sought to perform a preliminary evaluation of variation among the isolates in competitive ability against two high aflatoxin producers in laboratory assays on viable maize and peanut.  Isolate genetic diversity was evaluated with microsatellite (also called SSRs or Simple Sequence Repeats) analyses. Isolates with particular SSR haplotypes were not specific to either region or isolation date. Representative isolates for each of 6 haplotypes were compared for efficacy in the competition assay. Competition was performed in both maize grains and peanut pods. In order to determine influences of the selected fungi on the aflatoxin content of the crops aflatoxin production was quantified with quantitative TLC. In general, all six evaluated isolates (6) were able to both competitively displace the co-inoculated aflatoxin producing isolate and decrease aflatoxin concentrations in both crops. In peanut, the most effective aflatoxin contamination reducers of both of B1 and B2 were isolates AF100G and AFCHG2, with reduction percentages of 90 to 100% when paired with either aflatoxin-producer. In maize, isolates AFCHG2 and GD070 were the most effective at reducing contamination resulting in  94 and 78% reductions in total aflatoxins against aflatoxin producer AFCHG2 and, 93 and 92% against aflatoxin-producer GD070, respectively. The excellent in vivo results reported here supportevaluation of several of the tested non-aflatoxigenic isolates in aflatoxin management field trials either individually or in formulations that combine multiple non-aflatoxin producing isolates.