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Sweany RR, DeRobertis CD, Kaller MD, Damann KE. Intraspecific Growth and Aflatoxin Inhibition Responses to Atoxigenic Aspergillus flavus: Evidence of Secreted, Inhibitory Substances in Biocontrol. PHYTOPATHOLOGY 2022; 112:2084-2098. [PMID: 35502929 DOI: 10.1094/phyto-01-21-0022-r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The fungus Aspergillus flavus infects corn, peanut, and cottonseed, and contaminates seeds with acutely poisonous and carcinogenic aflatoxin. Aflatoxin contamination is a perennial threat in tropical and subtropical climates. Nonaflatoxin-producing isolates (atoxigenic) are deployed in fields to mitigate aflatoxin contamination. The biocontrol competitively excludes toxigenic A. flavus via direct replacement and thigmoregulated (touch) toxin inhibition mechanisms. To understand the broad-spectrum toxin inhibition, toxigenic isolates representing different mating types and sclerotia sizes were individually cocultured with different atoxigenic biocontrol isolates. To determine whether more inhibitory isolates had a competitive advantage to displace or touch inhibit toxigenic isolates, biomass accumulation rates were determined for each isolate. Finally, to determine whether atoxigenic isolates could inhibit aflatoxin production without touch, atoxigenic isolates were grown separated from a single toxigenic isolate by a membrane. Atoxigenic isolates 17, Af36, and K49 had superior abilities to inhibit toxin production. Small (<400 µm) sclerotial, Mat1-1 isolates were not as completely inhibited as others by most atoxigenic isolates. As expected for both direct replacement and touch inhibition, the fastest-growing atoxigenic isolates inhibited aflatoxin production the most, except for atoxigenic Af36 and K49. Aflatoxin production was inhibited when toxigenic and atoxigenic isolates were grown separately, especially by slow-growing atoxigenic Af36 and K49. Additionally, fungus-free filtrates from atoxigenic cultures inhibited aflatoxin production. Toxin production inhibition without direct contact revealed secretion of diffusible chemicals as an additional biocontrol mechanism. Biocontrol formulations should be improved by identifying isolates with broad-spectrum, high-inhibition capabilities and production of secreted inhibitory chemicals.
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Affiliation(s)
- Rebecca R Sweany
- Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge, LA 70803
| | - Catherine D DeRobertis
- Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge, LA 70803
| | - Michael D Kaller
- School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, LA 70803
| | - Kenneth E Damann
- Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge, LA 70803
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Assessment of the Potential of a Native Non-Aflatoxigenic Aspergillus flavus Isolate to Reduce Aflatoxin Contamination in Dairy Feed. Toxins (Basel) 2022; 14:toxins14070437. [PMID: 35878175 PMCID: PMC9319854 DOI: 10.3390/toxins14070437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 06/16/2022] [Accepted: 06/25/2022] [Indexed: 12/03/2022] Open
Abstract
Aspergillus species can produce aflatoxins (AFs), which can severely affect human and animal health. The objective was to evaluate the efficacy of reducing AF contamination of a non-aflatoxigenic isolate of A. flavus experimentally coinoculated with different aflatoxigenic strains in whole plant (WP), corn silage (CS), immature grains (IG) and in culture media (CM). An L-morphotype of A. flavus (CS1) was obtained from CS in a dairy farm located in the Mexican Highland Plateau; The CS1 failed to amplify the AFs biosynthetic pathway regulatory gene (aflR). Monosporic CS1 isolates were coinoculated in WP, CS, IG and CM, together with A. flavus strains with known aflatoxigenic capacity (originating from Cuautitlán and Tamaulipas, Mexico), and native isolates from concentrate feed (CF1, CF2 and CF3) and CS (CS2, CS3). AF production was evaluated by HPLC and fungal growth rate was measured on culture media. The positive control strains and those isolated from CF produced a large average amount of AFs (15,622 ± 3952 and 12,189 ± 3311 µg/kg), whereas A. flavus strains obtained from CS produced a lower AF concentration (126 ± 25.9 µg/kg). CS1 was efficient (p < 0.01) in decreasing AF concentrations when coinoculated together with CF, CS and aflatoxigenic positive control strains (71.6−88.7, 51.0−51.1 and 63.1−71.5%) on WP, CS, IG and CM substrates (73.9−78.2, 65.1−73.7, 63.8−68.4 and 57.4−67.6%). The results suggest that the non-aflatoxigenic isolate can be an effective tool to reduce AF contamination in feed and to minimize the presence of its metabolites in raw milk and dairy products intended for human nutrition.
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Inhibition of Aspergillus flavus Growth and Aflatoxin Production in Zea mays L. Using Endophytic Aspergillus fumigatus. J Fungi (Basel) 2022; 8:jof8050482. [PMID: 35628738 PMCID: PMC9146429 DOI: 10.3390/jof8050482] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Revised: 05/03/2022] [Accepted: 05/04/2022] [Indexed: 11/16/2022] Open
Abstract
Aspergillus flavus infection of vegetative tissues can affect the development and integrity of the plant and poses dangerous risks on human and animal health. Thus, safe and easily applied approaches are employed to inhibit A. flavus growth. To this end, the fungal endophyte, i.e., Aspergillus fumigatus, was used as a safe biocontrol agent to reduce the growth of A. flavus and its infection in maize seedlings. Interestingly, the safe endophytic A. fumigatus exhibited antifungal activity (e.g., 77% of growth inhibition) against A. flavus. It also reduced the creation of aflatoxins, particularly aflatoxin B1 (AFB1, 90.9%). At plant level, maize seedling growth, leaves and root anatomy and the changes in redox status were estimated. Infected seeds treated with A. fumigatus significantly improved the germination rate by 88.53%. The ultrastructure of the infected leaves showed severe disturbances in the internal structures, such as lack of differentiation in cells, cracking, and lysis in the cell wall and destruction in the nucleus semi-lysis of chloroplasts. Ultrastructure observations indicated that A. fumigatus treatment increased maize (leaf and root) cell wall thickness that consequentially reduced the invasion of the pathogenic A. flavus. It was also interesting that the infected seedlings recovered after being treated with A. fumigatus, as it was observed in growth characteristics and photosynthetic pigments. Moreover, infected maize plants showed increased oxidative stress (lipid peroxidation and H2O2), which was significantly mitigated by A. fumigatus treatment. This mitigation was at least partially explained by inducing the antioxidant defense system, i.e., increased phenols and proline levels (23.3 and 31.17%, respectively) and POD, PPO, SOD and CAT enzymes activity (29.50, 57.58, 32.14 and 29.52%, respectively). Overall, our study suggests that endophytic A. fumigatus treatment could be commercially used for the safe control of aflatoxins production and for inducing biotic stress tolerance of A. flavus-infected maize plants.
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Jia J, Ford E, Hobbs SM, Baird SM, Lu SE. Occidiofungin Is the Key Metabolite for Antifungal Activity of the Endophytic Bacterium Burkholderia sp. MS455 Against Aspergillus flavus. PHYTOPATHOLOGY 2022; 112:481-491. [PMID: 34433293 DOI: 10.1094/phyto-06-21-0225-r] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Aflatoxin is a secondary metabolite produced by Aspergillus fungi and presents a major food safety concern globally. Among the available methods for prevention and control of aflatoxin, the application of antifungal bacteria has gained favor in recent years. An endophytic bacterium MS455, isolated from soybean, exhibited broad-spectrum antifungal activity against economically important pathogens, including Aspergillus flavus. MS455 was identified as a strain of Burkholderia based on genomic analysis. Random and site-specific mutations were used in discovery of the genes that share high homology to the ocf gene cluster of Burkholderia contaminans strain MS14, which is responsible for production of the antifungal compound occidiofungin. RNA sequencing analysis demonstrated that ORF1, a homolog to the ambR1 LuxR-type regulatory gene, regulates occidiofungin biosynthesis in MS455. Additionally, 284 differentially expressed genes, including 138 upregulated and 146 downregulated genes, suggesting that, in addition to its role in occidiofungin production, ORF1 is involved in expression of multiple genes, especially those involved in ornibactin biosynthesis. Plate bioassays showed the growth of A. flavus was significantly inhibited by the wild-type strain MS455 as compared with the ORF1 mutant. Similarly, corn kernel assays showed that growth of A. flavus and aflatoxin production were reduced significantly by MS455 as compared with buffer control and the ORF1 mutant. Collectively, the results demonstrated that production of occidiofungin is essential for antifungal activity of the endophytic bacterium MS455. This research has provided insights about antifungal mechanisms of MS455 and development of biological approaches to prevent aflatoxin contamination in plant production.
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Affiliation(s)
- Jiayuan Jia
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS 39762
| | - Emerald Ford
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS 39762
| | - Sarah M Hobbs
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS 39762
| | - Sonya M Baird
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS 39762
| | - Shi-En Lu
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS 39762
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Sweany RR, Mack BM, Moore GG, Gilbert MK, Cary JW, Lebar MD, Rajasekaran K, Damann Jr. KE. Genetic Responses and Aflatoxin Inhibition during Co-Culture of Aflatoxigenic and Non-Aflatoxigenic Aspergillus flavus. Toxins (Basel) 2021; 13:794. [PMID: 34822579 PMCID: PMC8618995 DOI: 10.3390/toxins13110794] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 10/30/2021] [Accepted: 11/05/2021] [Indexed: 11/16/2022] Open
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 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.
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Affiliation(s)
- Rebecca R. Sweany
- Food and Feed Safety Research Unit, Southern Regional Research Center, US Department of Agriculture, New Orleans, LA 70124, USA; (B.M.M.); (M.K.G.); (J.W.C.); (M.D.L.)
- Department of Plant Pathology and Crop Physiology, Louisiana State University, Baton Rouge, LA 70808, USA;
| | - Brian M. Mack
- Food and Feed Safety Research Unit, Southern Regional Research Center, US Department of Agriculture, New Orleans, LA 70124, USA; (B.M.M.); (M.K.G.); (J.W.C.); (M.D.L.)
- Department of Plant Pathology and Crop Physiology, Louisiana State University, Baton Rouge, LA 70808, USA;
| | - Geromy G. Moore
- Food and Feed Safety Research Unit, Southern Regional Research Center, US Department of Agriculture, New Orleans, LA 70124, USA; (B.M.M.); (M.K.G.); (J.W.C.); (M.D.L.)
- Department of Plant Pathology and Crop Physiology, Louisiana State University, Baton Rouge, LA 70808, USA;
| | - Matthew K. Gilbert
- Food and Feed Safety Research Unit, Southern Regional Research Center, US Department of Agriculture, New Orleans, LA 70124, USA; (B.M.M.); (M.K.G.); (J.W.C.); (M.D.L.)
- Department of Plant Pathology and Crop Physiology, Louisiana State University, Baton Rouge, LA 70808, USA;
| | - Jeffrey W. Cary
- Food and Feed Safety Research Unit, Southern Regional Research Center, US Department of Agriculture, New Orleans, LA 70124, USA; (B.M.M.); (M.K.G.); (J.W.C.); (M.D.L.)
- Department of Plant Pathology and Crop Physiology, Louisiana State University, Baton Rouge, LA 70808, USA;
| | - Matthew D. Lebar
- Food and Feed Safety Research Unit, Southern Regional Research Center, US Department of Agriculture, New Orleans, LA 70124, USA; (B.M.M.); (M.K.G.); (J.W.C.); (M.D.L.)
- Department of Plant Pathology and Crop Physiology, Louisiana State University, Baton Rouge, LA 70808, USA;
| | - Kanniah Rajasekaran
- Food and Feed Safety Research Unit, Southern Regional Research Center, US Department of Agriculture, New Orleans, LA 70124, USA; (B.M.M.); (M.K.G.); (J.W.C.); (M.D.L.)
- Department of Plant Pathology and Crop Physiology, Louisiana State University, Baton Rouge, LA 70808, USA;
| | - Kenneth E. Damann Jr.
- Department of Plant Pathology and Crop Physiology, Louisiana State University, Baton Rouge, LA 70808, USA;
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Leiter É, Emri T, Pákozdi K, Hornok L, Pócsi I. The impact of bZIP Atf1ortholog global regulators in fungi. Appl Microbiol Biotechnol 2021; 105:5769-5783. [PMID: 34302199 PMCID: PMC8390427 DOI: 10.1007/s00253-021-11431-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 06/22/2021] [Accepted: 06/24/2021] [Indexed: 11/09/2022]
Abstract
Regulation of signal transduction pathways is crucial for the maintenance of cellular homeostasis and organismal development in fungi. Transcription factors are key elements of this regulatory network. The basic-region leucine zipper (bZIP) domain of the bZIP-type transcription factors is responsible for DNA binding while their leucine zipper structural motifs are suitable for dimerization with each other facilitiating the formation of homodimeric or heterodimeric bZIP proteins. This review highlights recent knowledge on the function of fungal orthologs of the Schizosaccharomyces pombe Atf1, Aspergillus nidulans AtfA, and Fusarium verticillioides FvAtfA, bZIP-type transcription factors with a special focus on pathogenic species. We demonstrate that fungal Atf1-AtfA-FvAtfA orthologs play an important role in vegetative growth, sexual and asexual development, stress response, secondary metabolite production, and virulence both in human pathogens, including Aspergillus fumigatus, Mucor circinelloides, Penicillium marneffei, and Cryptococcus neoformans and plant pathogens, like Fusarium ssp., Magnaporthe oryzae, Claviceps purpurea, Botrytis cinerea, and Verticillium dahliae. KEY POINTS: • Atf1 orthologs play crucial role in the growth and development of fungi. • Atf1 orthologs orchestrate environmental stress response of fungi. • Secondary metabolite production and virulence are coordinated by Atf1 orthologs.
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Affiliation(s)
- Éva Leiter
- Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, University of Debrecen, P.O. Box 63, Debrecen, H-4010, Hungary.
| | - Tamás Emri
- Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, University of Debrecen, P.O. Box 63, Debrecen, H-4010, Hungary
| | - Klaudia Pákozdi
- Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, University of Debrecen, P.O. Box 63, Debrecen, H-4010, Hungary
| | - László Hornok
- Hungarian University of Agriculture and Life Sciences, Gödöllő, Hungary
| | - István Pócsi
- Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, University of Debrecen, P.O. Box 63, Debrecen, H-4010, Hungary
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Yang K, Geng Q, Song F, He X, Hu T, Wang S, Tian J. Transcriptome Sequencing Revealed an Inhibitory Mechanism of Aspergillus flavus Asexual Development and Aflatoxin Metabolism by Soy-Fermenting Non-Aflatoxigenic Aspergillus. Int J Mol Sci 2020; 21:E6994. [PMID: 32977505 PMCID: PMC7583960 DOI: 10.3390/ijms21196994] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 09/12/2020] [Accepted: 09/17/2020] [Indexed: 11/16/2022] Open
Abstract
Aflatoxins (AFs) have always been regarded as the most effective carcinogens, posing a great threat to agriculture, food safety, and human health. Aspergillus flavus is the major producer of aflatoxin contamination in crops. The prevention and control of A. flavus and aflatoxin continues to be a global problem. In this study, we demonstrated that the cell-free culture filtrate of Aspergillus oryzae and a non-aflatoxigenic A. flavus can effectively inhibit the production of AFB1 and the growth and reproduction of A. flavus, indicating that both of the non-aflatoxigenic Aspergillus strains secrete inhibitory compounds. Further transcriptome sequencing was performed to analyze the inhibitory mechanism of A. flavus treated with fermenting cultures, and the results revealed that genes involved in the AF biosynthesis pathway and other biosynthetic gene clusters were significantly downregulated, which might be caused by the reduced expression of specific regulators, such as AflS, FarB, and MtfA. The WGCNA results further revealed that genes involved in the TCA cycle and glycolysis were potentially involved in aflatoxin biosynthesis. Our comparative transcriptomics also revealed that two conidia transcriptional factors, brlA and abaA, were found to be significantly downregulated, which might lead to the downregulation of conidiation-specific genes, such as the conidial hydrophobins genes rodA and rodB. In summary, our research provides new insights for the molecular mechanism of controlling AF synthesis to control the proliferation of A. flavus and AF pollution.
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Affiliation(s)
- Kunlong Yang
- School of Life Science, Jiangsu Normal University, Xuzhou 221116, China; (K.Y.); (Q.G.); (F.S.); (X.H.)
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China;
| | - Qingru Geng
- School of Life Science, Jiangsu Normal University, Xuzhou 221116, China; (K.Y.); (Q.G.); (F.S.); (X.H.)
| | - Fengqin Song
- School of Life Science, Jiangsu Normal University, Xuzhou 221116, China; (K.Y.); (Q.G.); (F.S.); (X.H.)
| | - Xiaona He
- School of Life Science, Jiangsu Normal University, Xuzhou 221116, China; (K.Y.); (Q.G.); (F.S.); (X.H.)
| | - Tianran Hu
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China;
| | - Shihua Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou 350002, China;
| | - Jun Tian
- School of Life Science, Jiangsu Normal University, Xuzhou 221116, China; (K.Y.); (Q.G.); (F.S.); (X.H.)
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Spadola G, Sanna V, Bartoli J, Carcelli M, Pelosi G, Bisceglie F, Restivo FM, Degola F, Rogolino D. Thiosemicarbazone nano-formulation for the control of Aspergillus flavus. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2020; 27:20125-20135. [PMID: 32239408 DOI: 10.1007/s11356-020-08532-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 03/20/2020] [Indexed: 05/27/2023]
Abstract
Nanoparticles are widely studied for applications in medical science. In recent years, they have been developed for agronomical purposes to target microbial pest such as bacteria, fungi, and viruses. Nanoparticles are also proposed to limit the use of pesticides, whose abuse is causing environmental impact and human health concerns. In this study, nanoparticles were obtained by using poly-(ε-caprolactone), a polyester chosen for its biocompatibility and biodegradability properties. Poly-(ε-caprolactone) nanoparticles were formulated by using poly(vinyl alcohol) or Pluronic® F127 as non-ionic surfactants, and then loaded with benzophenone or valerophenone thiosemicarbazone, two compounds that inhibit aflatoxin production by Aspergillus flavus. The different types of nanoparticles were compared in terms of size, polydispersity index, morphology, and drug loading capacity. Finally, their effects were investigated on growth, development, and aflatoxin production in the aflatoxigenic species Aspergillus flavus, a ubiquitous contaminant of maize, cereal crops, and derived commodities. Aflatoxin production was inhibited to various extents, but the best inhibitory effect was obtained with respect to sclerotia production that was most effectively suppressed by both benzophenone and valerophenone thiosemicarbazone-loaded nanoparticles. These data support the idea that it is possible to use such nanoparticles as an alternate to pesticides for the control of mycotoxigenic sclerotia-forming fungi.
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Affiliation(s)
- Giorgio Spadola
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 11/A, 43124, Parma, Italy
| | - Vanna Sanna
- Nanomater Srl Porto Conte Ricerche, Loc. Tramariglio, 07041, Alghero, SS, Italy
| | - Jennifer Bartoli
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 11/A, 43124, Parma, Italy
| | - Mauro Carcelli
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 11/A, 43124, Parma, Italy
| | - Giorgio Pelosi
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 11/A, 43124, Parma, Italy
| | - Franco Bisceglie
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 11/A, 43124, Parma, Italy
| | - Francesco Maria Restivo
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 11/A, 43124, Parma, Italy
| | - Francesca Degola
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 11/A, 43124, Parma, Italy
| | - Dominga Rogolino
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 11/A, 43124, Parma, Italy.
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Lagat MK, Toroitich FJ, Obonyo MA. Development of an ELISA-based method for testing aflatoxigenicity and aflatoxigenic variability among Aspergillus species in culture. SCIENTIFIC AFRICAN 2020. [DOI: 10.1016/j.sciaf.2020.e00266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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Yazid SNE, Jinap S, Ismail SI, Magan N, Samsudin NIP. Phytopathogenic organisms and mycotoxigenic fungi: Why do we control one and neglect the other? A biological control perspective in Malaysia. Compr Rev Food Sci Food Saf 2020; 19:643-669. [DOI: 10.1111/1541-4337.12541] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2019] [Revised: 01/03/2020] [Accepted: 01/08/2020] [Indexed: 01/06/2023]
Affiliation(s)
- Siti Nur Ezzati Yazid
- Laboratory of Food Safety and Food IntegrityInstitute of Tropical Agriculture and Food Security, Universiti Putra Malaysia Serdang Malaysia
| | - Selamat Jinap
- Laboratory of Food Safety and Food IntegrityInstitute of Tropical Agriculture and Food Security, Universiti Putra Malaysia Serdang Malaysia
- Department of Food Science, Faculty of Food Science and TechnologyUniversiti Putra Malaysia Serdang Malaysia
| | - Siti Izera Ismail
- Laboratory of Climate‐Smart Food Crop ProductionInstitute of Tropical Agriculture and Food Security, Universiti Putra Malaysia Serdang Malaysia
- Department of Plant ProtectionFaculty of AgricultureUniversiti Putra Malaysia Serdang Malaysia
| | - Naresh Magan
- Applied Mycology GroupCranfield Soil and AgriFood InstituteCranfield University Cranfield UK
| | - Nik Iskandar Putra Samsudin
- Laboratory of Food Safety and Food IntegrityInstitute of Tropical Agriculture and Food Security, Universiti Putra Malaysia Serdang Malaysia
- Department of Food Science, Faculty of Food Science and TechnologyUniversiti Putra Malaysia Serdang Malaysia
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Hua SST, Parfitt DE, Sarreal SBL, Sidhu G. Dual culture of atoxigenic and toxigenic strains of Aspergillus flavus to gain insight into repression of aflatoxin biosynthesis and fungal interaction. Mycotoxin Res 2019; 35:381-389. [PMID: 31161589 DOI: 10.1007/s12550-019-00364-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Revised: 03/27/2019] [Accepted: 05/06/2019] [Indexed: 11/24/2022]
Abstract
Application of atoxigenic strains to compete against toxigenic strains of Aspergillus flavus strains has emerged as one of the practical strategies for reducing aflatoxin contamination in corn, peanut, and tree nuts. The actual mechanism that results in aflatoxin reduction is not fully understood. Real-time RT-PCR and relative quantification of gene expression protocol were applied to elucidate the molecular mechanism. Transcriptional analyses of aflatoxin biosynthetic gene cluster in dual culture of toxigenic and atoxigenic A. flavus strains were carried out. Six targeted genes, aflR, aflJ, omtA, ordA, pksA, and vbs, were downregulated to variable levels depending on paired strains of toxigenic and atoxigenic A. flavus. Consistent with the decreased gene expression levels, the aflatoxin concentrations in dual cultures were reduced significantly in comparison with toxigenic cultures. Fluorescent images showed fungal hyphae in dual culture displayed green fluorescent, and contacts of live hyphae were seen. A coconut agar plate assay was used to show that toxigenic A. flavus colony produced blue fluorescence under long UV exposure, suggesting that aflatoxin is exported outside fungal hyphae. Furthermore, the assay was applied to demonstrate the potential role of thigmo-regulation in fungal interaction.
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Affiliation(s)
- Sui Sheng T Hua
- U.S. Department of Agriculture, Agricultural Research Service, Western Regional Research Center, 800 Buchanan Street, Albany, CA, 94710, USA.
| | - Dan E Parfitt
- Department of Plant Sciences, University of California, Davis, One Shields Avenue, Davis, CA, 95616, USA
| | - Siov Bouy L Sarreal
- U.S. Department of Agriculture, Agricultural Research Service, Western Regional Research Center, 800 Buchanan Street, Albany, CA, 94710, USA
| | - Gaganjot Sidhu
- U.S. Department of Agriculture, Agricultural Research Service, Western Regional Research Center, 800 Buchanan Street, Albany, CA, 94710, USA
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Zhou Y, Wang J, Gao X, Wang K, Wang W, Wang Q, Yan P. Isolation of a novel deep-sea Bacillus circulus strain and uniform design for optimization of its anti-aflatoxigenic bioactive metabolites production. Bioengineered 2019; 10:13-22. [PMID: 30836830 PMCID: PMC6527075 DOI: 10.1080/21655979.2019.1586055] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The deep-sea bacterium strain FA13 was isolated from the sediment of the South Atlantic Ocean and identified as Bacillus circulans based on 16S ribosomal DNA sequence. Through liquid fermentation with five media, the cell-free supernatant fermented with ISP2 showed the highest inhibition activities against mycelial growth of Aspergillus parasiticus mutant strain NFRI-95 and accumulation of norsolorinic acid, a precursor for aflatoxin production. Based on ISP2, uniform design was used to optimize medium formula and fermentation conditions. After optimization, the inhibition efficacy of the 20-time diluted supernatant against A. parasiticus NFRI-95 mycelial growth and aflatoxin production was increased from 0–23.1% to 100%. Moreover, compared to the original protocol, medium cost and fermentation temperature were significantly reduced, and dependence on seawater was completely relieved, thus preventing the fermentor from corrosion. This is the first report of a deep-sea microorganism which can inhibit A. parasiticus NFRI-95 mycelial growth and aflatoxin production.
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Affiliation(s)
- Ying Zhou
- a School of Marine Science and Technology , Harbin Institute of Technology , Weihai , Shandong , China.,b Key Laboratory of Marine Biogenetic Resources , Third Institute of Oceanography, State Oceanic Administration , Xiamen , China
| | - Jingying Wang
- a School of Marine Science and Technology , Harbin Institute of Technology , Weihai , Shandong , China
| | - Xiujun Gao
- a School of Marine Science and Technology , Harbin Institute of Technology , Weihai , Shandong , China
| | - Kai Wang
- a School of Marine Science and Technology , Harbin Institute of Technology , Weihai , Shandong , China
| | - Wenwei Wang
- a School of Marine Science and Technology , Harbin Institute of Technology , Weihai , Shandong , China
| | - Qi Wang
- a School of Marine Science and Technology , Harbin Institute of Technology , Weihai , Shandong , China
| | - Peisheng Yan
- a School of Marine Science and Technology , Harbin Institute of Technology , Weihai , Shandong , China
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13
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Moore G, Lebar M, Carter‐Wientjes C. The role of extrolites secreted by nonaflatoxigenicAspergillus flavusin biocontrol efficacy. J Appl Microbiol 2019; 126:1257-1264. [DOI: 10.1111/jam.14175] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 10/09/2018] [Accepted: 12/06/2018] [Indexed: 11/30/2022]
Affiliation(s)
- G.G. Moore
- US Department of Agriculture Agricultural Research Service, Southern Regional Research Center New Orleans LA USA
| | - M.D. Lebar
- US Department of Agriculture Agricultural Research Service, Southern Regional Research Center New Orleans LA USA
| | - C.H. Carter‐Wientjes
- US Department of Agriculture Agricultural Research Service, Southern Regional Research Center New Orleans LA USA
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14
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Alshannaq AF, Gibbons JG, Lee MK, Han KH, Hong SB, Yu JH. Controlling aflatoxin contamination and propagation of Aspergillus flavus by a soy-fermenting Aspergillus oryzae strain. Sci Rep 2018; 8:16871. [PMID: 30442975 PMCID: PMC6237848 DOI: 10.1038/s41598-018-35246-1] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 10/31/2018] [Indexed: 01/09/2023] Open
Abstract
Aflatoxins (AFs) are a group of carcinogenic and immunosuppressive mycotoxins that threaten global food safety. Globally, over 4.5 billion people are exposed to unmonitored levels of AFs. Aspergillus flavus is the major source of AF contamination in agricultural crops. One approach to reduce levels of AFs in agricultural commodities is to apply a non-aflatoxigenic competitor, e.g., Afla-Guard, to crop fields. In this study, we demonstrate that the food fermenting Aspergillus oryzae M2040 strain, isolated from Korean Meju (a brick of dry-fermented soybeans), can inhibit aflatoxin B1 (AFB1) production and proliferation of toxigenic A. flavus in lab culture conditions and peanuts. In peanuts, 1% inoculation level of A. oryzae M2040 could effectively displace the toxigenic A. flavus and inhibit AFB1 production. Moreover, cell-free culture filtrate of A. oryzae M2040 effectively inhibited AFB1 production and A. flavus growth, suggesting A. oryzae M2040 secretes inhibitory compounds. Whole genome-based comparative analyses indicate that the A. oryzae M2040 and Afla-Guard genomes are 37.9 and 36.4 Mbp, respectively, with each genome containing ~100 lineage specific genes. Our study establishes the idea of using A. oryzae and/or its cell-free culture fermentate as a potent biocontrol agent to control A. flavus propagation and AF contamination.
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Affiliation(s)
- Ahmad F Alshannaq
- Department of Food Science, University of Wisconsin-Madison, 1605 Linden Dr, Madison, WI, 53706, USA
- Food Research Institute, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI, 53706, USA
| | - John G Gibbons
- Department of Food Science, University of Massachusetts, 240 Chenoweth Laboratory, 102 Holdsworth Way, Amherst, MA, 01003, USA
| | - Mi-Kyung Lee
- Biological resource center, Korea Research Institute of Bioscience and Biotechnology, 181 Ipsin-gil, Jeongeup-si, Jeollabuk-do, 56212, Republic of Korea
| | - Kap-Hoon Han
- Department of Pharmaceutical Engineering, Woosuk University, Wanju, 55338, Republic of Korea
| | - Seung-Beom Hong
- Korean Agricultural Culture Collection, Agricultural Microbiology Division, NAS, RDA, Wanju, Republic of Korea
| | - Jae-Hyuk Yu
- Food Research Institute, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI, 53706, USA.
- Department of Bacteriology, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI, 53706, USA.
- Department of Systems Biotechnology, Konkuk University, Seoul, Republic of Korea.
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15
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Ojiambo PS, Battilani P, Cary JW, Blum BH, Carbone I. Cultural and Genetic Approaches to Manage Aflatoxin Contamination: Recent Insights Provide Opportunities for Improved Control. PHYTOPATHOLOGY 2018; 108:1024-1037. [PMID: 29869954 DOI: 10.1094/phyto-04-18-0134-rvw] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Aspergillus flavus is a morphologically complex species that can produce the group of polyketide derived carcinogenic and mutagenic secondary metabolites, aflatoxins, as well as other secondary metabolites such as cyclopiazonic acid and aflatrem. Aflatoxin causes aflatoxicosis when aflatoxins are ingested through contaminated food and feed. In addition, aflatoxin contamination is a major problem, from both an economic and health aspect, in developing countries, especially Asia and Africa, where cereals and peanuts are important food crops. Earlier measures for control of A. flavus infection and consequent aflatoxin contamination centered on creating unfavorable environments for the pathogen and destroying contaminated products. While development of atoxigenic (nonaflatoxin producing) strains of A. flavus as viable commercial biocontrol agents has marked a unique advance for control of aflatoxin contamination, particularly in Africa, new insights into the biology and sexuality of A. flavus are now providing opportunities to design improved atoxigenic strains for sustainable biological control of aflatoxin. Further, progress in the use of molecular technologies such as incorporation of antifungal genes in the host and host-induced gene silencing, is providing knowledge that could be harnessed to develop germplasm that is resistant to infection by A. flavus and aflatoxin contamination. This review summarizes the substantial progress that has been made to understand the biology of A. flavus and mitigate aflatoxin contamination with emphasis on maize. Concepts developed to date can provide a basis for future research efforts on the sustainable management of aflatoxin contamination.
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Affiliation(s)
- Peter S Ojiambo
- First and fifth authors: Center for Integrated Fungal Research, Department of Entomology and Plant Pathology, North Carolina State University, Raleigh 27695; second author: Department of Sustainable Crop Production, Università Cattolica del Sacro Cuore, Via Emilia Parmense 84, 29122 Piacenza, Italy; third author: U.S. Department of Agriculture-Agriculture Research Service, SRRC, New Orleans, LA 70124; and fourth author: Department of Plant Pathology, University of Arkansas, Fayetteville 72701
| | - Paola Battilani
- First and fifth authors: Center for Integrated Fungal Research, Department of Entomology and Plant Pathology, North Carolina State University, Raleigh 27695; second author: Department of Sustainable Crop Production, Università Cattolica del Sacro Cuore, Via Emilia Parmense 84, 29122 Piacenza, Italy; third author: U.S. Department of Agriculture-Agriculture Research Service, SRRC, New Orleans, LA 70124; and fourth author: Department of Plant Pathology, University of Arkansas, Fayetteville 72701
| | - Jeffrey W Cary
- First and fifth authors: Center for Integrated Fungal Research, Department of Entomology and Plant Pathology, North Carolina State University, Raleigh 27695; second author: Department of Sustainable Crop Production, Università Cattolica del Sacro Cuore, Via Emilia Parmense 84, 29122 Piacenza, Italy; third author: U.S. Department of Agriculture-Agriculture Research Service, SRRC, New Orleans, LA 70124; and fourth author: Department of Plant Pathology, University of Arkansas, Fayetteville 72701
| | - Burt H Blum
- First and fifth authors: Center for Integrated Fungal Research, Department of Entomology and Plant Pathology, North Carolina State University, Raleigh 27695; second author: Department of Sustainable Crop Production, Università Cattolica del Sacro Cuore, Via Emilia Parmense 84, 29122 Piacenza, Italy; third author: U.S. Department of Agriculture-Agriculture Research Service, SRRC, New Orleans, LA 70124; and fourth author: Department of Plant Pathology, University of Arkansas, Fayetteville 72701
| | - Ignazio Carbone
- First and fifth authors: Center for Integrated Fungal Research, Department of Entomology and Plant Pathology, North Carolina State University, Raleigh 27695; second author: Department of Sustainable Crop Production, Università Cattolica del Sacro Cuore, Via Emilia Parmense 84, 29122 Piacenza, Italy; third author: U.S. Department of Agriculture-Agriculture Research Service, SRRC, New Orleans, LA 70124; and fourth author: Department of Plant Pathology, University of Arkansas, Fayetteville 72701
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Chalivendra SC, DeRobertis C, Chang PK, Damann KE. Cyclopiazonic Acid Is a Pathogenicity Factor for Aspergillus flavus and a Promising Target for Screening Germplasm for Ear Rot Resistance. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2017; 30:361-373. [PMID: 28447887 DOI: 10.1094/mpmi-02-17-0026-r] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Aspergillus flavus, an opportunistic pathogen, contaminates maize and other key crops with carcinogenic aflatoxins (AFs). Besides AFs, A. flavus makes many more secondary metabolites (SMs) whose toxicity in insects or vertebrates has been studied. However, the role of SMs in the invasion of plant hosts by A. flavus remains to be investigated. Cyclopiazonic acid (CPA), a neurotoxic SM made by A. flavus, is a nanomolar inhibitor of endoplasmic reticulum calcium ATPases (ECAs) and a potent inducer of cell death in plants. We hypothesized that CPA, by virtue of its cytotoxicity, may serve as a key pathogenicity factor that kills plant cells and supports the saprophytic life style of the fungus while compromising the host defense response. This proposal was tested by two complementary approaches. A comparison of CPA levels among A. flavus isolates indicated that CPA may be a determinant of niche adaptation, i.e., isolates that colonize maize make more CPA than those restricted only to the soil. Further, mutants in the CPA biosynthetic pathway are less virulent in causing ear rot than their wild-type parent in field inoculation assays. Additionally, genes encoding ECAs are expressed in developing maize seeds and are induced by A. flavus infection. Building on these results, we developed a seedling assay in which maize roots were exposed to CPA, and cell death was measured as Evans Blue uptake. Among >40 maize inbreds screened for CPA tolerance, inbreds with proven susceptibility to ear rot were also highly CPA sensitive. The publicly available data on resistance to silk colonization or AF contamination for many of the lines was also broadly correlated with their CPA sensitivity. In summary, our studies show that i) CPA serves as a key pathogenicity factor that enables the saprophytic life style of A. flavus and ii) maize inbreds are diverse in their tolerance to CPA. Taking advantage of this natural variation, we are currently pursuing both genome-wide and candidate gene approaches to identify novel components of maize resistance to Aspergillus ear rot.
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Affiliation(s)
| | | | - Perng-Kuang Chang
- 2 USDA-Southern Region Research Center, New Orleans, LA 70124, U.S.A
| | - Kenneth E Damann
- 1 Louisiana State University Ag Center, Baton Rouge, LA 70803, U.S.A.; and
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Bandyopadhyay R, Ortega-Beltran A, Akande A, Mutegi C, Atehnkeng J, Kaptoge L, Senghor A, Adhikari B, Cotty P. Biological control of aflatoxins in Africa: current status and potential challenges in the face of climate change. WORLD MYCOTOXIN J 2016. [DOI: 10.3920/wmj2016.2130] [Citation(s) in RCA: 180] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Aflatoxin contamination of crops is frequent in warm regions across the globe, including large areas in sub-Saharan Africa. Crop contamination with these dangerous toxins transcends health, food security, and trade sectors. It cuts across the value chain, affecting farmers, traders, markets, and finally consumers. Diverse fungi within Aspergillus section Flavi contaminate crops with aflatoxins. Within these Aspergillus communities, several genotypes are not capable of producing aflatoxins (atoxigenic). Carefully selected atoxigenic genotypes in biological control (biocontrol) formulations efficiently reduce aflatoxin contamination of crops when applied prior to flowering in the field. This safe and environmentally friendly, effective technology was pioneered in the US, where well over a million acres of susceptible crops are treated annually. The technology has been improved for use in sub-Saharan Africa, where efforts are under way to develop biocontrol products, under the trade name Aflasafe, for 11 African nations. The number of participating nations is expected to increase. In parallel, state of the art technology has been developed for large-scale inexpensive manufacture of Aflasafe products under the conditions present in many African nations. Results to date indicate that all Aflasafe products, registered and under experimental use, reduce aflatoxin concentrations in treated crops by >80% in comparison to untreated crops in both field and storage conditions. Benefits of aflatoxin biocontrol technologies are discussed along with potential challenges, including climate change, likely to be faced during the scaling-up of Aflasafe products. Lastly, we respond to several apprehensions expressed in the literature about the use of atoxigenic genotypes in biocontrol formulations. These responses relate to the following apprehensions: sorghum as carrier, distribution costs, aflatoxin-conscious markets, efficacy during drought, post-harvest benefits, risk of allergies and/or aspergillosis, influence of Aflasafe on other mycotoxins and on soil microenvironment, dynamics of Aspergillus genotypes, and recombination between atoxigenic and toxigenic genotypes in natural conditions.
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Affiliation(s)
- R. Bandyopadhyay
- International Institute of Tropical Agriculture (IITA), PMB 5320, Oyo Road, 200001 Ibadan, Nigeria
| | - A. Ortega-Beltran
- International Institute of Tropical Agriculture (IITA), PMB 5320, Oyo Road, 200001 Ibadan, Nigeria
| | - A. Akande
- IITA, PMB 82, Garki GPO, Kubwa, Abuja, Nigeria
| | - C. Mutegi
- IITA, ILRI campus, P.O. Box 30772-00100, Nairobi, Kenya
| | - J. Atehnkeng
- IITA, Chitedze Research Station, Off Mchinji Road, P.O. Box 30258, Lilongwe 3, Malawi
| | - L. Kaptoge
- International Institute of Tropical Agriculture (IITA), PMB 5320, Oyo Road, 200001 Ibadan, Nigeria
| | - A.L. Senghor
- La Direction de la Protection des Végétaux (DPV), Km 15, Route de Rufisque, en face Forail, BP 20054, Thiaroye-Dakar, Senegal
| | - B.N. Adhikari
- USDA-ARS, School of Plant Sciences, University of Arizona, P.O. Box 210036, Tucson, AZ 85721-0036, USA
| | - P.J. Cotty
- USDA-ARS, School of Plant Sciences, University of Arizona, P.O. Box 210036, Tucson, AZ 85721-0036, USA
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18
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Alberts JF, van Zyl WH, Gelderblom WCA. Biologically Based Methods for Control of Fumonisin-Producing Fusarium Species and Reduction of the Fumonisins. Front Microbiol 2016; 7:548. [PMID: 27199904 PMCID: PMC4845651 DOI: 10.3389/fmicb.2016.00548] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 04/04/2016] [Indexed: 12/03/2022] Open
Abstract
Infection by the fumonisin-producing Fusarium spp. and subsequent fumonisin contamination of maize adversely affect international trade and economy with deleterious effects on human and animal health. In developed countries high standards of the major food suppliers and retailers are upheld and regulatory controls deter the importation and local marketing of fumonisin-contaminated food products. In developing countries regulatory measures are either lacking or poorly enforced, due to food insecurity, resulting in an increased mycotoxin exposure. The lack and poor accessibility of effective and environmentally safe control methods have led to an increased interest in practical and biological alternatives to reduce fumonisin intake. These include the application of natural resources, including plants, microbial cultures, genetic material thereof, or clay minerals pre- and post-harvest. Pre-harvest approaches include breeding for resistant maize cultivars, introduction of biocontrol microorganisms, application of phenolic plant extracts, and expression of antifungal proteins and fumonisin degrading enzymes in transgenic maize cultivars. Post-harvest approaches include the removal of fumonisins by natural clay adsorbents and enzymatic degradation of fumonisins through decarboxylation and deamination by recombinant carboxylesterase and aminotransferase enzymes. Although, the knowledge base on biological control methods has expanded, only a limited number of authorized decontamination products and methods are commercially available. As many studies detailed the use of natural compounds in vitro, concepts in reducing fumonisin contamination should be developed further for application in planta and in the field pre-harvest, post-harvest, and during storage and food-processing. In developed countries an integrated approach, involving good agricultural management practices, hazard analysis and critical control point (HACCP) production, and storage management, together with selected biologically based treatments, mild chemical and physical treatments could reduce fumonisin contamination effectively. In rural subsistence farming communities, simple, practical, and culturally acceptable hand-sorting, maize kernel washing, and dehulling intervention methods proved to be effective as a last line of defense for reducing fumonisin exposure. Biologically based methods for control of fumonisin-producing Fusarium spp. and decontamination of the fumonisins could have potential commercial application, while simple and practical intervention strategies could also impact positively on food safety and security, especially in rural populations reliant on maize as a dietary staple.
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Affiliation(s)
- Johanna F. Alberts
- Mycotoxicology and Chemoprevention Research Group, Institute of Biomedical and Microbial Biotechnology, Cape Peninsula University of TechnologyBellville, South Africa
| | - Willem H. van Zyl
- Microbiology Department, Stellenbosch UniversityStellenbosch, South Africa
| | - Wentzel C. A. Gelderblom
- Mycotoxicology and Chemoprevention Research Group, Institute of Biomedical and Microbial Biotechnology, Cape Peninsula University of TechnologyBellville, South Africa
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19
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Mylroie JE, Ozkan S, Shivaji R, Windham GL, Alpe MN, Williams WP. Identification and Quantification of a Toxigenic and Non-Toxigenic Aspergillus flavus Strain in Contaminated Maize Using Quantitative Real-Time PCR. Toxins (Basel) 2016; 8:E15. [PMID: 26742074 PMCID: PMC4728537 DOI: 10.3390/toxins8010015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 12/17/2015] [Accepted: 12/28/2015] [Indexed: 11/16/2022] Open
Abstract
Aflatoxins, which are produced by Aspergillus flavus, are toxic to humans, livestock, and pets. The value of maize (Zea mays) grain is markedly reduced when contaminated with aflatoxin. Plant resistance and biological control using non-toxin producing strains are considered effective strategies for reducing aflatoxin accumulation in maize grain. Distinguishing between the toxin and non-toxin producing strains is important in determining the effectiveness of bio-control strategies and understanding inter-strain interactions. Using polymorphisms found in the fungal rRNA intergenic spacer region (IGS) between a toxigenic strain of A. flavus (NRRL 3357) and the non-toxigenic strain used in the biological control agent Afla-Guard(®) (NRRL 21882), we developed a set of primers that allows for the identification and quantification of the two strains using quantitative PCR. This primer set has been used to screen maize grain that was inoculated with the two strains individually and co-inoculated with both strains, and it has been shown to be effective in both the identification and quantification of both strains. Screening of co-inoculated ears from multiple resistant and susceptible genotypic crosses revealed no significant differences in fungal biomass accumulation of either strain in the field tests from 2010 and 2011 when compared across the means of all genotypes. Only one genotype/year combination showed significant differences in strain accumulation. Aflatoxin accumulation analysis showed that, as expected, genotypes inoculated with the toxigenic strain accumulated more aflatoxin than when co-inoculated with both strains or inoculated with only the non-toxigenic strain. Furthermore, accumulation of toxigenic fungal mass was significantly correlated with aflatoxin accumulation while non-toxigenic fungal accumulation was not. This primer set will allow researchers to better determine how the two fungal strains compete on the maize ear and investigate the interaction between different maize lines and these A. flavus strains.
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Affiliation(s)
- J Erik Mylroie
- United States Department of Agriculture, Agricultural Research Service, Corn Host Plant Resistance Research Unit, Mississippi State City, MS 39762, USA.
| | - Seval Ozkan
- Department of Plant and Soil Sciences, Mississippi State University, Mississippi State City, MS 39762, USA.
| | - Renuka Shivaji
- University of North Carolina at Greensboro Molecular Core Lab, University of North Carolina at Greensboro, Greensboro, NC 27412, USA.
| | - Gary L Windham
- United States Department of Agriculture, Agricultural Research Service, Corn Host Plant Resistance Research Unit, Mississippi State City, MS 39762, USA.
| | - Michael N Alpe
- United States Department of Agriculture, Agricultural Research Service, Corn Host Plant Resistance Research Unit, Mississippi State City, MS 39762, USA.
| | - W Paul Williams
- United States Department of Agriculture, Agricultural Research Service, Corn Host Plant Resistance Research Unit, Mississippi State City, MS 39762, USA.
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