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  • Callicott, Kenneth A.  (5)
  • 1
    Online Resource
    Online Resource
    Table_2.docx
    Frontiers Media SA ; 2020
    In:  Frontiers in Microbiology Vol. 11 ( 2020-6-11)
    Details
    In: Frontiers in Microbiology, Frontiers Media SA, Vol. 11 ( 2020-6-11)
    Type of Medium: Online Resource
    ISSN: 1664-302X
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    URL: Article
    DOI: 10.3389/fmicb.2020.01236
    DOI: 10.3389/fmicb.2020.01236.s001
    DOI: 10.3389/fmicb.2020.01236.s002
    DOI: 10.3389/fmicb.2020.01236.s003
    DOI: 10.3389/fmicb.2020.01236.s004
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2020
    detail.hit.zdb_id: 2587354-4
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  • 2
    Online Resource
    Online Resource
    Degradation of Aflatoxins B 1 by Atoxigenic Aspergillus flavus Biocontrol Agents
    Scientific Societies ; 2021
    In:  Plant Disease Vol. 105, No. 9 ( 2021-09-01), p. 2343-2350
    Details
    In: Plant Disease, Scientific Societies, Vol. 105, No. 9 ( 2021-09-01), p. 2343-2350
    Abstract: Aflatoxins are potent Aspergillus mycotoxins that contaminate food and feed, thereby impacting health and trade. Biopesticides with atoxigenic Aspergillus flavus isolates as active ingredients are used to reduce aflatoxin contamination in crops. The mechanism of aflatoxin biocontrol is primarily attributed to competitive exclusion but, sometimes, aflatoxin is reduced by greater amounts than can be explained by displacement of aflatoxin-producing fungi on the crop. Objectives of this study were to (i) evaluate the ability of atoxigenic A. flavus genotypes to degrade aflatoxin B 1 (AFB1) and (ii) characterize impacts of temperature, time, and nutrient availability on AFB1 degradation by atoxigenic A. flavus. Aflatoxin-contaminated maize was inoculated with atoxigenic isolates in three separate experiments that included different atoxigenic genotypes, temperature, and time as variables. Atoxigenic genotypes varied in aflatoxin degradation but all degraded AFB1 〉 44% after 7 days at 30°C. The optimum temperature for AFB1 degradation was 25 to 30°C, which is similar to the optimum range for AFB1 production. In a time-course experiment, atoxigenics degraded 40% of AFB1 within 3 days, and 80% of aflatoxin was degraded by day 21. Atoxigenic isolates were able to degrade and utilize AFB1 as a sole carbon source in a chemically defined medium but quantities of AFB1 degraded declined as glucose concentrations increased. Degradation may be an additional mechanism through which atoxigenic A. flavus biocontrol products reduce aflatoxin contamination pre- or postharvest. Thus, selection of optimal atoxigenic active ingredients can include assessment of both competitive ability in agricultural fields and their ability to degrade aflatoxins.
    Type of Medium: Online Resource
    ISSN: 0191-2917 , 1943-7692
    URL: Article
    DOI: 10.1094/PDIS-01-21-0066-RE
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2021
    detail.hit.zdb_id: 2042679-3
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  • 3
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    Online Resource
    Phenotypic Differentiation of Two Morphologically Similar Aflatoxin-Producing Fungi from West Africa
    MDPI AG ; 2020
    In:  Toxins Vol. 12, No. 10 ( 2020-10-13), p. 656-
    Details
    In: Toxins, MDPI AG, Vol. 12, No. 10 ( 2020-10-13), p. 656-
    Abstract: Aflatoxins (AF) are hepatocarcinogenic metabolites produced by several Aspergillus species. Crop infection by these species results in aflatoxin contamination of cereals, nuts, and spices. Etiology of aflatoxin contamination is complicated by mixed infections of multiple species with similar morphology and aflatoxin profiles. The current study investigates variation in aflatoxin production between two morphologically similar species that co-exist in West Africa, A. aflatoxiformans and A. minisclerotigenes. Consistent distinctions in aflatoxin production during liquid fermentation were discovered between these species. The two species produced similar concentrations of AFB1 in defined media with either urea or ammonium as the sole nitrogen source. However, production of both AFB1 and AFG1 were inhibited (p 〈 0.001) for A. aflatoxiformans in a yeast extract medium with sucrose. Although production of AFG1 by both species was similar in urea, A. minisclerotigenes produced greater concentrations of AFG1 in ammonium (p = 0.039). Based on these differences, a reliable and convenient assay for differentiating the two species was designed. This assay will be useful for identifying specific etiologic agents of aflatoxin contamination episodes in West Africa and other regions where the two species are sympatric, especially when phylogenetic analyses based on multiple gene segments are not practical.
    Type of Medium: Online Resource
    ISSN: 2072-6651
    URL: Article
    DOI: 10.3390/toxins12100656
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2518395-3
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  • 4
    Online Resource
    Online Resource
    Temperature Influences on Interactions Among Aflatoxigenic Species of Aspergillus Section Flavi During Maize Colonization
    Frontiers Media SA ; 2021
    In:  Frontiers in Fungal Biology Vol. 2 ( 2021-8-26)
    Details
    In: Frontiers in Fungal Biology, Frontiers Media SA, Vol. 2 ( 2021-8-26)
    Abstract: Fungal species within Aspergillus section Flavi contaminate food and feed with aflatoxins. These toxic fungal metabolites compromise human and animal health and disrupt trade. Genotypically and phenotypically diverse species co-infect crops, but temporal and spatial variation in frequencies of different lineages suggests that environmental factors such as temperature may influence structure of aflatoxin-producing fungal communities. Furthermore, though most species within Aspergillus section Flavi produce sclerotia, divergent sclerotial morphologies (small or S-type sclerotia vs. large or L-type sclerotia) and differences in types and quantities of aflatoxins produced suggest lineages are adapted to different life strategies. Temperature is a key parameter influencing pre- and post-harvest aflatoxin contamination of crops. We tested the hypothesis that species of aflatoxin-producing fungi that differ in sclerotial morphology will vary in competitive ability and that outcomes of competition and aflatoxin production will be modulated by temperature. Paired competition experiments between highly aflatoxigenic S-type species ( A. aflatoxiformans and Lethal Aflatoxicosis Fungus) and L-type species ( A. flavus L morphotype and A. parasiticus ) were conducted on maize kernels at 25 and 30°C. Proportions of each isolate growing within and sporulating on kernels were measured using quantitative pyrosequencing. At 30°C, S-type fungi were more effective at host colonization compared to L-type isolates. Total aflatoxins and the proportion of B vs. G aflatoxins were greater at 30°C compared to 25°C. Sporulation by L-type isolates was reduced during competition with S-type fungi at 30°C, while relative quantities of conidia produced by S-type species either increased or did not change during competition. Results indicate that both species interactions and temperature can shape population structure of Aspergillus section Flavi , with warmer temperatures favoring growth and dispersal of highly toxigenic species with S-type sclerotia.
    Type of Medium: Online Resource
    ISSN: 2673-6128
    URL: Article
    DOI: 10.3389/ffunb.2021.720276
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2021
    detail.hit.zdb_id: 3059082-6
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  • 5
    Online Resource
    Online Resource
    Genetic Diversity of Aspergillus flavus Associated with Chili in Nigeria and Identification of Haplotypes with Potential in Aflatoxin Mitigation
    Scientific Societies ; 2022
    In:  Plant Disease Vol. 106, No. 7 ( 2022-07-01), p. 1818-1825
    Details
    In: Plant Disease, Scientific Societies, Vol. 106, No. 7 ( 2022-07-01), p. 1818-1825
    Abstract: Dried red chili (Capsicum spp.), a widely produced and consumed spice in Nigeria, is often contaminated by aflatoxins. Aflatoxins are potent mycotoxins of severe health and economic concern worldwide. Aspergillus flavus often contaminates crops with aflatoxins in warm regions; however, not all isolates are aflatoxin producers. Nonaflatoxigenic isolates have potential as biocontrol agents for aflatoxin mitigation. The current study examined the genetic diversity of A. flavus (n = 325) associated with chilies in Nigeria and identified 123 nonaflatoxigenic isolates. The Nigerian A. flavus isolates from chili were diverse at 17 microsatellite loci, with 5 to 36 alleles per locus, and included 152 haplotypes. The isolates that are active ingredients in Aflasafe, registered for aflatoxin biocontrol on maize and groundnuts in Nigeria, did not share haplotypes with the chili isolates. Of the 152 haplotypes, 65% produced aflatoxins in autoclaved maize, some of which (17%) produced 〉 100,000 µg/kg of aflatoxins. Aflatoxins were not detected in 35% of the haplotypes. Cluster amplification pattern assay detected large deletions in the aflatoxin biosynthetic clusters of some (32%) of the nonaflatoxigenic haplotypes. Coinfection of chili with nonaflatoxigenic isolates from chilies (n = 7) and A. aflatoxiformans resulted in a significantly greater average reduction in total aflatoxins compared with that achieved by Aflasafe active ingredient isolates (P 〈 0.01). These nonaflatoxigenic isolates are a genetic resource for the development of biological control products for aflatoxin mitigation in chilies in Nigeria and should be evaluated under field conditions.
    Type of Medium: Online Resource
    ISSN: 0191-2917 , 1943-7692
    URL: Article
    DOI: 10.1094/PDIS-07-21-1464-RE
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2022
    detail.hit.zdb_id: 2042679-3
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