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Detection of Aflatoxigenic and Atoxigenic Mexican Aspergillus Strains by the Dichlorvos–Ammonia (DV–AM) Method

Masayo Kushiro Alexander Loladze (2018)

The dichlorvos–ammonia (DV–AM) method is a sensitive method for distinguishing aflatoxigenic fungi by detecting red (positive) colonies. In this study, the DV–AM method was applied for the isolation of aflatoxigenic and atoxigenic fungi from soil samples from a maize field in Mexico. In the first screening, we obtained two isolates from two soil subsamples of 20 independent samples and, in the second screening, we obtained two isolates from one subsample of these. Morphological and phylogenic analyses of the two isolates (MEX-A19-13, MEX-A19-2nd-5) indicated that they were Aspergillus flavus located in the A. flavus clade. Chemical analyses demonstrated that one isolate could produce B-type aflatoxins, while the other produced no aflatoxins. These results demonstrate that the DV–AM method is useful for the isolation of both aflatoxigenic and atoxigenic Aspergilli.


Dichlorvos Aspergillus flavus Aflatoxins Aflatoxin B1 Aflatoxin B2 Fungal Strain MAIZE ALATOXINS CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA

Variation in occurrence and aflatoxigenicity of Aspergillus flavus from two climatically varied regions in Kenya

amos Alakonya (2020)

Aflatoxins are carcinogenic chemical metabolites produced by Aspergillus spp. of the section Flavi. In Kenya, Aspergillus flavus is the most prevalent and has been associated with several acute and chronic aflatoxin outbreaks in the past. In this study, we evaluated the occurrence of A. flavus in soils from two agro-ecological regions with contrasting climatic conditions, aflatoxin contamination histories and cropping systems. Aspergillus spp. were first isolated from soils before the identification and determination of their aflatoxigenicity. Further, we determined the occurrence of Pseudomonas and Bacillus spp. in soils from the two regions. These bacterial species have long been associated with biological control of several plant pathogens including Aspergillus spp. Our results show that A. flavus occurred widely and produced comparatively higher total aflatoxin levels in all (100%) study sites from the eastern to the western regions of Kenya. For the western region, A. flavus was detected in 4 locations (66.7%) that were previously under maize cultivation with the isolates showing low aflatoxigenicity. A. flavus was not isolated from soils under sugarcane cultivation. Distribution of the two bacterial species varied across the regions but we detected a weak relationship between occurrence of bacterial species and A. flavus. We discuss these findings in the context of the influence of climate, microbial profiles, cropping systems and applicability in the deployment of biological control remedies against aflatoxin contamination.



Provitamin A carotenoids in grain reduce aflatoxin contamination of maize while combating vitamin A deficiency

natalia palacios rojas Jose Crossa (2019)

Aflatoxin contamination of maize grain and products causes serious health problems for consumers worldwide, and especially in low- and middle-income countries where monitoring and safety standards are inconsistently implemented. Vitamin A deficiency (VAD) also compromises the health of millions of maize consumers in several regions of the world including large parts of sub-Saharan Africa. We investigated whether provitamin A (proVA) enriched maize can simultaneously contribute to alleviate both of these health concerns. We studied aflatoxin accumulation in grain of 120 maize hybrids formed by crossing 3 Aspergillus flavus resistant and three susceptible lines with 20 orange maize lines with low to high carotenoids concentrations. The hybrids were grown in replicated, artificially-inoculated field trials at five environments. Grain of hybrids with larger concentrations of beta-carotene (BC), beta-cryptoxanthin (BCX) and total proVA had significantly less aflatoxin contamination than hybrids with lower carotenoids concentrations. Aflatoxin contamination had negative genetic correlation with BCX (-0.28, p < 0.01), BC (-0.18, p < 0.05), and proVA (-0.23, p < 0.05). The relative ease of breeding for increased proVA carotenoid concentrations as compared to breeding for aflatoxin resistance in maize suggests using the former as a component of strategies to combat aflatoxin contamination problems for maize. Our findings indicate that proVA enriched maize can be particularly beneficial where the health burdens of exposure to aflatoxin and prevalence of VAD converge with high rates of maize consumption.



Detección de hongos e identificación de micotoxinas en granos de maíz almacenados.


Tesis (Maestría en Ciencias, especialista en Producción Agroalimentaria en el Trópico).- Colegio de Postgraduados, 2019.

Los hongos del género Aspergillus producen metabolitos secundarios tóxicos llamados aflatoxinas (AF) que invaden y afectan los granos como el maíz. Estas sustancias producen efectos negativos en humanos y animales, afectando el metabolismo de carbohidratos, lípidos y proteínas. Se procedió a realizar un muestreo en ocho establecimientos que comercializan granos de maíz, localizados en Cárdenas, Tabasco. Mediante la técnica de microcultivo se aislaron y caracterizaron morfológicamente cepas de hongos del género Aspergillus spp. y Cunninghamella spp., además, mediante Cromatografía Líquida de Alta Resolución (HPLC) acoplada a un detector de UV-VIS, se determinó la presencia de cuatro tipos de AF (AFB1, AFB2, AFG1 y AFG2), los cuales presentaron concentraciones que oscilaban entre 55.22 y 1256.35 µg kg-1. Las muestras analizadas superaron el nivel máximo permisible de 20 µg kg-1 para aflatoxinas, establecido por las Normas Oficiales Mexicanas. _______________ DETECTION OF FUNGI AND IDENTIFICATION OF MYCOTOXINS IN STORED MAIZE GRAINS. ABSTRACT: Fungi of the genus Aspergillus invade and affect grains such as corn, and produce toxic secondary metabolites called aflatoxins (AF), which produce negative effects in humans and animals, affecting the metabolism of carbohydrates, lipids and proteins. Based on this, we proceeded to carry out a sampling in eight establishments that sell corn grain, wich are located in Cárdenas, Tabasco. Using the microculture technique, fungal strains of the genus Aspergillus spp., and Cunninghamella spp., were morphologically isolated and characterized; Furthermore, by means of high performance liquid chromatography (HPLC) coupled to a detector UV-VIS, the presence of four types of AF (AFB1, AFB2, AFG1 and AFG2) was determined, with presented concentrations ranging between 55.22 and 1256.35 μg kg-1. The samples analyzed exceed the maximum permissible level of AF, which should not exceed 20 μg kg-1, established by the Official Mexican Standards.

Master thesis

Aspergillus Aflatoxinas HPLC Límite máximo permisible Aflatoxins Maximum permissible levels Producción Agroalimentaria en el Trópico Maestría CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA CIENCIAS AGRARIAS AGRONOMÍA SEMILLAS