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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #318367
Title: Effects of hydrogen peroxide on different toxigenic and atoxigenic isolates of Aspergillus flavus

Author
item FOUNTAIN, JAKE - University Of Georgia
item Scully, Brian
item CHEN, ZHI-YUAN - Louisiana State University
item Gold, Scott
item Glenn, Anthony - Tony
item Abbas, Hamed
item LEE, R - University Of Georgia
item KEMERAIT, ROBERT - University Of Georgia
item Guo, Baozhu

Submitted to: Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/2015
Publication Date: 8/5/2015
Citation: Fountain, J.C., Scully, B.T., Chen, Z., Gold, S.E., Glenn, A.E., Abbas, H.K., Lee, R.D., Kemerait, R.C., Guo, B. 2015. Effects of hydrogen peroxide on different toxigenic and atoxigenic isolates of Aspergillus flavus. Toxins. 7:2985-2999.

Interpretive Summary: The contamination with aflatoxin in corn and peanut has been shown to be exacerbated by the presence of drought stress and related abiotic stresses. Aflatoxin production can be also exacerbated by reactive oxygen species (ROS). The objectives of this study were to examine the effects of hydrogen peroxide (H2O2)-induced oxidative stress on the growth of different toxigenic (+) and atoxigenic (-) isolates of Aspergillus flavus and to test whether aflatoxin production affects the H2O2 concentrations that the isolates could survive. Ten different isolates were tested. These isolates were cultured under a H2O2 gradient ranging from 0 to 50 mM in two different media, aflatoxin-conducive yeast extract-sucrose (YES) and non-conducive yeast extract-peptone (YEP). Fungal growth was inhibited at a high H2O2 concentration, but specific isolates grew well at different H2O2 concentrations. Generally the toxigenic isolates tolerated higher concentrations than did atoxigenic isolates. Increasing H2O2 concentrations in the media resulted in elevated aflatoxin production in toxigenic isolates. In YEP media, the higher concentration of peptone (15%) partially inactivated the H2O2 in the media. In the 1% peptone media, YEP did not affect the H2O2 concentrations that the isolates could survive in comparison with YES media. It is interesting to note that the commercial biocontrol isolates, AF36(-), and Aflaguard(-), survived at higher levels of stress than other atoxigenic isolates, suggesting that this testing method could potentially be of use in the selection of biocontrol isolates.

Technical Abstract: Drought stress in the field has been shown to exacerbate aflatoxin contamination of maize and peanut. Drought and heat stress also produce reactive oxygen species (ROS) in plant tissues. Given the potential correlation between ROS and exacerbated aflatoxin production under drought and heat stress, the objectives of this study were to examine the effects of hydrogen peroxide (H2O2)-induced oxidative stress on the growth of different toxigenic (+) and atoxigenic (-) isolates of Aspergillus flavus and to test whether aflatoxin production affects the H2O2 concentrations that the isolates could survive. Ten isolates were tested: NRRL3357(+), A9(+), AF13(+), Tox4(+), A1(-), K49(-), K54A(-), AF36(-), and Aflaguard(-); and one A. parasiticus isolate, NRRL2999(+). These isolates were cultured under a H2O2 gradient ranging from 0 to 50 mM in two different media, aflatoxin-conducive yeast extract-sucrose (YES) and non-conducive yeast extract-peptone (YEP). Fungal growth was inhibited at a high H2O2 concentration, but specific isolates grew well at different H2O2 concentrations. Generally the toxigenic isolates tolerated higher concentrations than did atoxigenic isolates. Increasing H2O2 concentrations in the media resulted in elevated aflatoxin production in toxigenic isolates. In YEP media, the higher concentration of peptone (15%) partially inactivated the H2O2 in the media. In the 1% peptone media, YEP did not affect the H2O2 concentrations that the isolates could survive in comparison with YES media, without aflatoxin production. It is interesting to note that the commercial biocontrol isolates, AF36(-), and Aflaguard(-), survived at higher levels of stress than other atoxigenic isolates, suggesting that this testing method could potentially be of use in the selection of biocontrol isolates. Further studies will be needed to investigate the mechanisms behind the variability among isolates with regard to their degree of oxidative stress tolerance and the role of aflatoxin production.