Location: Food and Feed Safety Research
2018 Annual Report
Accomplishments
1. Mechanism(s) by which Aspergillus (A.) flavus biocontrol strains reduce aflatoxin contamination. Significant control of aflatoxin contamination of crops has been achieved through biocontrol using atoxigenic strains of the fungus. However, the mechanism of biocontrol is not known for atoxigenic A. flavus strains. One mode may be through chemical compounds produced by the biocontrol strain. Experiments have been performed to determine the role that fungal extrolites (compounds excreted by the fungus, many of which may have growth-inhibiting properties) may play in the efficacy of biocontrol strains. It has been determined by Agricultural Research Service researchers in New Orleans, Louisiana, that at least one uncharacterized extrolite compound secreted by the atoxigenic strain included in this study reduced growth of toxigenic A. flavus and A. parasiticus strains on two types of growth medium (4-45%), as well as aflatoxin B1 by 60-78%. Once we identify and characterize the inhibitory extrolite(s) secreted by the atoxigenic strain, they will be synthesized and tested as a spray treatment, or will be used as a screen for future biocontrol strains that readily produce the inhibiting compound(s).
2. Mechanism(s) by which Aspergillus (A.) flavus biocontrol strains reduce aflatoxin contamination. Significant control of aflatoxin contamination of crops has been achieved through biocontrol using atoxigenic strains of the fungus. However, the mechanism of biocontrol is not known for atoxigenic A. flavus strains. One mode may be through chemical compounds produced by the biocontrol strain. So far, experiments have been performed to determine the role that previously characterized toxigenic A. flavus VOCs (volatile organic compounds emitted by the toxigenic fungus that may inhibit growth of competing fungi) may have on four Louisiana strains tested. It has been determined by Agricultural Research Service researchers in New Orleans, Louisiana, that benzaldehyde may be an important VOC since its exposure to all strains resulted in reduced growth as volume of the VOC increased, including the atoxigenic strain. Aflatoxin B1 reduction, consistent with increased VOC, was observed for only one strain, LA4 (Aspergillus parasiticus), when exposed to benzaldehyde and eucalyptol, which may mean these compounds are not naturally produced by A. parasiticus. By elucidating the impact of benzaldehyde exposure on the atoxigenic strain, future biocontrol strains should be screened for competitive resistance to production of this VOC by toxigenic A. flavus, which could enhance their effectiveness.
Review Publications
Moore, G.G., Olarte, R.A., Horn, B.W., Elliott, J.L., Singh, R., O'Neal, C.J., Carbone, I. 2017. Global population structure and adaptive evolution of aflatoxin-producing fungi. Ecology and Evolution. 7:9179-9191.
Moore, G.G., Mack, B.M., Beltz, S.B., Puel, O. 2018. Genome sequence of an aflatoxigenic pathogen of Argentinian peanut, Aspergillus arachidicola. BMC Genomics. 19:189. https://doi.org/10.1186/s12864-018-4576-2.
Carvajal-Campos, A., Manizan, A.L., Tadrist, S., Akaki, D.K., Koffi-Nevry, R., Moore, G.G., Fapohunda, S.O., Bailly, S., Montet, D., Oswald, I.P., Lorber, S., Brabet, C., Puel, O. 2017. Aspergillus korhogoensis, a novel aflatoxin producing species from the Côte d’Ivoire. Toxins. 9:353. https://doi.org/10.3390/toxins9110353.
Ozturk, I.K., Chettri, P., Dupont, P-Y., Barnes, I., McDougal, R.L., Moore, G.G., Sim, A., Bradshaw, R.E. 2017. Evolution of polyketide synthesis in a Dothideomycete forest pathogen. Fungal Genetics and Biology. 106:42-50.
