Competitive exclusion by atoxigenic strains of Aspergillus flavus is worldwide accepted as the only preventive action, effective to minimize aflatoxins contamination in several crops, maize included. Maize lots, uncompliant with the European legislation, were signaled almost all years. After the first outbreak of aflatoxin in maize in 2003 in Italy, followed by severe contamination in 2012 and 2015, but lot uncompliant with the European legislation signaled almost all years, the selection of candidate biocontrol agents among native strains started. USA, Africa and Italy have now commercial products available, but Eastern Europe need to be considered too. The aim of this study was select A. flavus candidate biocontrol agents in Romania. For this purpose, 139 maize flour samples, representative of the whole Romanian maize growing areas, were used for the isolation of Aspergillus section Flavi strains. Among them, 188 representative strains were chosen, identified (sequencing the beta-tubulin gene region), processed and characterized. Deletions of the aflatoxin gene cluster region were investigated by multiplex PCR analyses (using a set of 16 primer pairs) to select potential biocontrol agents to be included in competition tests. The size of microsatellite alleles retrieved from 18 markers, out of the 24 tested, were bioinformatically analysed to uncover the population structure. 169 strains were confirmed as A. flavus; 71 strains seems to lack at least one gene of the aflatoxin cluster and, among these, 7 strains seems to lack all the genes and were chosen for further investigations. Microsatellites analysis allowed us to identify two main groups by bayesian cluster analysis, genetic distance based analyses and population assignment. The 7 atoxigenic strains demonstrated to be very effective in reducing aflatoxins (ranged between 80 and 96%) when co-inoculated with toxigenic strains. A potential candidate to be used as biocontrol agent was finally selected on the basis of competition tests and microsatellites results and, its efficacy, will be hopefully confirmed during in field trials.
Characterization of Aspergillus flavus population native of Romania.
Perrone G;Magistà D;Logrieco A F;
2018
Abstract
Competitive exclusion by atoxigenic strains of Aspergillus flavus is worldwide accepted as the only preventive action, effective to minimize aflatoxins contamination in several crops, maize included. Maize lots, uncompliant with the European legislation, were signaled almost all years. After the first outbreak of aflatoxin in maize in 2003 in Italy, followed by severe contamination in 2012 and 2015, but lot uncompliant with the European legislation signaled almost all years, the selection of candidate biocontrol agents among native strains started. USA, Africa and Italy have now commercial products available, but Eastern Europe need to be considered too. The aim of this study was select A. flavus candidate biocontrol agents in Romania. For this purpose, 139 maize flour samples, representative of the whole Romanian maize growing areas, were used for the isolation of Aspergillus section Flavi strains. Among them, 188 representative strains were chosen, identified (sequencing the beta-tubulin gene region), processed and characterized. Deletions of the aflatoxin gene cluster region were investigated by multiplex PCR analyses (using a set of 16 primer pairs) to select potential biocontrol agents to be included in competition tests. The size of microsatellite alleles retrieved from 18 markers, out of the 24 tested, were bioinformatically analysed to uncover the population structure. 169 strains were confirmed as A. flavus; 71 strains seems to lack at least one gene of the aflatoxin cluster and, among these, 7 strains seems to lack all the genes and were chosen for further investigations. Microsatellites analysis allowed us to identify two main groups by bayesian cluster analysis, genetic distance based analyses and population assignment. The 7 atoxigenic strains demonstrated to be very effective in reducing aflatoxins (ranged between 80 and 96%) when co-inoculated with toxigenic strains. A potential candidate to be used as biocontrol agent was finally selected on the basis of competition tests and microsatellites results and, its efficacy, will be hopefully confirmed during in field trials.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
