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Toxins
Special Issues
Current Status and Challenges of Aflatoxin Biocontrol Strategies
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Current Status and Challenges of Aflatoxin Biocontrol Strategies

A special issue of Toxins (ISSN 2072-6651). This special issue belongs to the section "Mycotoxins".

Deadline for manuscript submissions: closed (30 June 2023) | Viewed by 12321

Special Issue Editors

Dr. Geromy G. Moore

E-Mail Website
Guest Editor
USDA Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, USA
Interests: mechanisms of biocontrol; pre-harvest; post-harvest; induced host resistance; stability; fungal diversity; biopesticides; food or feed crops; aflatoxin contamination
Dr. Hillary L. Mehl

E-Mail Website
Guest Editor
USDA Agricultural Research Service, Pest Management and Biocontrol Research, Maricopa, Arizona, USA
Dr. Kenneth A. Callicott

E-Mail Website
Guest Editor
USDA Agricultural Research Service, Pest Management and Biocontrol Research, Maricopa, Arizona, USA

Special Issue Information

Dear Colleagues,

Aflatoxin contamination of agricultural commodities is a global issue with potentially significant economic and health impacts. There are disparities between countries with regard to the impact of, and approach to, the aflatoxin problem, with Low to Middle Income Countries (LMICs) experiencing more of the detrimental effects of aflatoxin contamination. Research to prevent infection by aflatoxin producing fungi, mitigate the negative effects associated with aflatoxin contamination, and develop resistant or defensible plant hosts offers opportunities to ensure a safe food and feed supply. The implementation of biological control strategies (either direct or indirect) are preferred and continue to be explored, especially over use of potentially harmful chemical fungicides. However, research is still needed to develop effective, affordable biocontrol products and strategies to for target crops and regions worldwide where aflatoxin contamination events are frequent and severe. Furthermore, the benefits of combining aflatoxin biocontrol with other aflatoxin and general crop management tactics needs to be explored. Therefore, the goal of this Special Issue is to showcase the many different avenues of research that relate to sustainable pre-harvest or post-harvest biological control of aflatoxin producing fungi.

Dr. Geromy G. Moore
Dr. Hillary L. Mehl
Dr. Kenneth A. Callicott
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a double-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Toxins is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Aspergillus section Flavi
  • mechanisms of biocontrol
  • pre-harvest
  • post-harvest
  • induced host
  • resistance
  • stability
  • climatic impacts
  • fungal diversity
  • biopesticides
  • food or feed crops

Published Papers (5 papers)

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Research

15 pages, 948 KiB  
Article
Multiple Year Influences of the Aflatoxin Biocontrol Product AF-X1 on the A. flavus Communities Associated with Maize Production in Italy
by Mohamed Ali Ouadhene, Alejandro Ortega-Beltran, Martina Sanna, Peter J. Cotty and Paola Battilani
Toxins 2023, 15(3), 184; https://0-doi-org.brum.beds.ac.uk/10.3390/toxins15030184 - 28 Feb 2023
Cited by 5 | Viewed by 1413
Abstract
AF-X1 is a commercial aflatoxin biocontrol product containing the non-aflatoxigenic (AF-) strain of Aspergillus flavus MUCL54911 (VCG IT006), endemic to Italy, as an active ingredient. The present study aimed to evaluate the long-term persistence of VCG IT006 in the treated fields, and the [...] Read more.
AF-X1 is a commercial aflatoxin biocontrol product containing the non-aflatoxigenic (AF-) strain of Aspergillus flavus MUCL54911 (VCG IT006), endemic to Italy, as an active ingredient. The present study aimed to evaluate the long-term persistence of VCG IT006 in the treated fields, and the multi-year influence of the biocontrol application on the A. flavus population. Soil samples were collected in 2020 and 2021 from 28 fields located in four provinces in north Italy. A vegetative compatibility analysis was conducted to monitor the occurrence of VCG IT006 on the total of the 399 isolates of A. flavus that were collected. IT006 was present in all the fields, mainly in the fields treated for 1 yr or 2 consecutive yrs (58% and 63%, respectively). The densities of the toxigenic isolates, detected using the aflR gene, were 45% vs. 22% in the untreated and treated fields, respectively. After displacement via the AF- deployment, a variability from 7% to 32% was noticed in the toxigenic isolates. The current findings support the long-term durability of the biocontrol application benefits without deleterious effects on each fungal population. Nevertheless, based on the current results, as well as on previous studies, the yearly applications of AF-X1 to Italian commercial maize fields should continue. Full article
(This article belongs to the Special Issue Current Status and Challenges of Aflatoxin Biocontrol Strategies)
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11 pages, 1720 KiB  
Article
Characterization of the Aspergillus flavus Population from Highly Aflatoxin-Contaminated Corn in the United States
by Mark A. Weaver, Kenneth A. Callicott, Hillary L. Mehl, Joseph Opoku, Lilly C. Park, Keiana S. Fields and Jennifer R. Mandel
Toxins 2022, 14(11), 755; https://0-doi-org.brum.beds.ac.uk/10.3390/toxins14110755 - 02 Nov 2022
Cited by 2 | Viewed by 2021
Abstract
Aflatoxin contamination of corn is a major threat to the safe food and feed. The United States Federal Grain Inspection Service (FGIS) monitors commercial grain shipments for the presence of aflatoxin. A total of 146 Aspergillus flavus were isolated from 29 highly contaminated [...] Read more.
Aflatoxin contamination of corn is a major threat to the safe food and feed. The United States Federal Grain Inspection Service (FGIS) monitors commercial grain shipments for the presence of aflatoxin. A total of 146 Aspergillus flavus were isolated from 29 highly contaminated grain samples to characterize the visual phenotypes, aflatoxin-producing potential, and genotypes to explore the etiological cause of high aflatoxin contamination of US corn. Five of the isolates had reduced sensitivity (43–49% resistant) to the fungicide azoxystrobin, with the remainder all being over 50% resistant to azoxystrobin at the discriminating dose of 2.5 µg/mL. Only six isolates of the highly aflatoxigenic S morphotype were found, and 48 isolates were non-aflatoxigenic. Analysis of the mating type locus revealed 45% MAT 1-1 and 55% MAT 1-2. The A. flavus population originating from the highly aflatoxin contaminated grain samples was compared to a randomly selected subset of isolates originating from commercial corn samples with typical levels of aflatoxin contamination (average < 50 ppb). Use of simple sequence repeat (SSR) genotyping followed by principal component analysis (PCoA) revealed a similar pattern of genotypic distribution in the two populations, but greater diversity in the FGIS-derived population. The noticeable difference between the two populations was that genotypes identical to strain NRRL 21882, the active component of the aflatoxin biocontrol product Afla-Guard™, were ten times more common in the commercial corn population of A. flavus compared to the population from the high-aflatoxin corn samples. The other similarities between the two populations suggest that high aflatoxin concentrations in corn grain are generally the result of infection with common A. flavus genotypes. Full article
(This article belongs to the Special Issue Current Status and Challenges of Aflatoxin Biocontrol Strategies)
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11 pages, 1463 KiB  
Article
Cumulative Effects of Non-Aflatoxigenic Aspergillus flavus Volatile Organic Compounds to Abate Toxin Production by Mycotoxigenic Aspergilli
by Geromy G. Moore, Matthew D. Lebar and Carol H. Carter-Wientjes
Toxins 2022, 14(5), 340; https://0-doi-org.brum.beds.ac.uk/10.3390/toxins14050340 - 13 May 2022
Cited by 6 | Viewed by 1995
Abstract
Previously, authors reported that individual volatile organic compounds (VOCs) emitted by non-aflatoxigenic Aspergillus flavus could act as a mechanism of biocontrol to significantly reduce aflatoxins and cyclopiazonic acid (CPA) produced by toxigenic strains. In this study, various combinations and volumes of three mycotoxin-reductive [...] Read more.
Previously, authors reported that individual volatile organic compounds (VOCs) emitted by non-aflatoxigenic Aspergillus flavus could act as a mechanism of biocontrol to significantly reduce aflatoxins and cyclopiazonic acid (CPA) produced by toxigenic strains. In this study, various combinations and volumes of three mycotoxin-reductive VOCs (2,3-dihydrofuran, 3-octanone and decane) were assessed for their cumulative impacts on four Aspergillus strains (LA1–LA4), which were then analyzed for changes in growth, as well as the production of mycotoxins, including aflatoxins, CPA and multiple indole diterpenes. Fungal growth remained minimally inhibited when exposed to various combinations of VOCs. No single combination was able to consistently, or completely, inhibit aflatoxin or CPA across all toxigenic strains tested. However, the combination of 2,3-dihydrofuran and 3-octanone offered the greatest overall reductions in aflatoxin and CPA production. Despite no elimination of their production, findings showed that combining VOCs produced solely by non-aflatoxigenic A. flavus still inhibited several agriculturally important mycotoxins, including B and G aflatoxins and CPA. Therefore, other VOC combinations are worth testing as post-harvest biocontrol treatments to ensure the prolonged effectiveness of pre-harvest biocontrol efforts. Full article
(This article belongs to the Special Issue Current Status and Challenges of Aflatoxin Biocontrol Strategies)
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14 pages, 2333 KiB  
Article
Characterization of Ugandan Endemic Aspergillus Species and Identification of Non-Aflatoxigenic Isolates for Potential Biocontrol of Aflatoxins
by Godfrey Wokorach, Sofie Landschoot, Amerida Lakot, Sidney Arihona Karyeija, Kris Audenaert, Richard Echodu and Geert Haesaert
Toxins 2022, 14(5), 304; https://0-doi-org.brum.beds.ac.uk/10.3390/toxins14050304 - 26 Apr 2022
Cited by 2 | Viewed by 2724
Abstract
Acute stunting in children, liver cancer, and death often occur due to human exposure to aflatoxins in food. The severity of aflatoxin contamination depends on the type of Aspergillus fungus infecting the crops. In this study, Aspergillus species were isolated from households’ staple [...] Read more.
Acute stunting in children, liver cancer, and death often occur due to human exposure to aflatoxins in food. The severity of aflatoxin contamination depends on the type of Aspergillus fungus infecting the crops. In this study, Aspergillus species were isolated from households’ staple foods and were characterized for different aflatoxin chemotypes. The non-aflatoxigenic chemotypes were evaluated for their ability to reduce aflatoxin levels produced by aflatoxigenic A. flavus strains on maize grains. Aspergillus flavus (63%), A. tamarii (14%), and A. niger (23%) were the main species present. The A. flavus species included isolates that predominantly produced aflatoxins B1 and B2, with most isolates producing a high amount (>20 ug/µL) of aflatoxin B1 (AFB1), and a marginal proportion of them also producing G aflatoxins with a higher level of aflatoxin G1 (AFG1) than AFB1. Some non-aflatoxigenic A. tamarii demonstrated a strong ability to reduce the level of AFB1 by more than 95% when co-inoculated with aflatoxigenic A. flavus. Therefore, field evaluation of both non-aflatoxigenic A. flavus and A. tamarii would be an important step toward developing biocontrol agents for mitigating field contamination of crops with aflatoxins in Uganda. Full article
(This article belongs to the Special Issue Current Status and Challenges of Aflatoxin Biocontrol Strategies)
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21 pages, 1132 KiB  
Article
Genetic Responses and Aflatoxin Inhibition during Co-Culture of Aflatoxigenic and Non-Aflatoxigenic Aspergillus flavus
by Rebecca R. Sweany, Brian M. Mack, Geromy G. Moore, Matthew K. Gilbert, Jeffrey W. Cary, Matthew D. Lebar, Kanniah Rajasekaran and Kenneth E. Damann, Jr.
Toxins 2021, 13(11), 794; https://0-doi-org.brum.beds.ac.uk/10.3390/toxins13110794 - 11 Nov 2021
Cited by 10 | Viewed by 2893
Abstract
Aflatoxin is a carcinogenic mycotoxin produced by Aspergillus flavus. Non-aflatoxigenic (Non-tox) A. flavus isolates are deployed in corn fields as biocontrol because they substantially reduce aflatoxin contamination via direct replacement and additionally via direct contact or touch with toxigenic (Tox) isolates and [...] Read more.
Aflatoxin is a carcinogenic mycotoxin produced by Aspergillus flavus. Non-aflatoxigenic (Non-tox) A. flavus isolates are deployed in corn fields as biocontrol because they substantially reduce aflatoxin contamination via direct replacement and additionally via direct contact or touch with toxigenic (Tox) isolates and secretion of inhibitory/degradative chemicals. To understand touch inhibition, HPLC analysis and RNA sequencing examined aflatoxin production and gene expression of Non-tox isolate 17 and Tox isolate 53 mono-cultures and during their interaction in co-culture. Aflatoxin production was reduced by 99.7% in 72 h co-cultures. Fewer than expected unique reads were assigned to Tox 53 during co-culture, indicating its growth and/or gene expression was inhibited in response to Non-tox 17. Predicted secreted proteins and genes involved in oxidation/reduction were enriched in Non-tox 17 and co-cultures compared to Tox 53. Five secondary metabolite (SM) gene clusters and kojic acid synthesis genes were upregulated in Non-tox 17 compared to Tox 53 and a few were further upregulated in co-cultures in response to touch. These results suggest Non-tox strains can inhibit growth and aflatoxin gene cluster expression in Tox strains through touch. Additionally, upregulation of other SM genes and redox genes during the biocontrol interaction demonstrates a potential role of inhibitory SMs and antioxidants as additional biocontrol mechanisms and deserves further exploration to improve biocontrol formulations. Full article
(This article belongs to the Special Issue Current Status and Challenges of Aflatoxin Biocontrol Strategies)
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