Assessment of early harvest in the prevention of aflatoxins in peanuts during drought stress conditions

The present study aimed to evaluate the effectiveness of early harvest in preventing aflatoxins in peanuts under drought-stress conditions. A field experiment was conducted on the 2018-2019 and 2019-2020 growing seasons in a greenhouse with an irrigation system to induce three drought stress conditions: no stress, mild, and severe stress. In addition, three harvest dates were proposed: two weeks earlier, one week earlier, and ideal harvest time. The mean peanut yield was 2634 kg/ha, considering the two growing seasons, and the drought stress conditions and harvest dates did not influence significantly. The shelling percentage was significantly higher in samples harvested at ideal harvest (77.7 %) than two weeks earlier (76.2 %) and was not influenced by drought stress conditions. Although a low mean percentage of grains with insect damage was identified, this percentage was statistically higher under severe stress (0.4 %) compared to no-stress conditions (0.2 %). The soil contamination ranged from 2.52 × 103 to 1.64 × 104 CFU/g of Aspergillus section Flavi, and the drought stress resulted in significantly higher concentrations in mild and severe stressed samples. A. section Flavi was found to infect all the peanut kernel samples. The drought stress resulted in higher percentages of A. section Flavi infections in samples from mild and severe stress conditions. The harvest date did not influence the soil and peanut kernel occurrence of A. section Flavi. A total of 435 and 796 strains of A. section Flavi were isolated from soil and peanut kernels, respectively. The potential of aflatoxin production by soil isolates was 31, 44, and 25 % for aflatoxin non-producers, aflatoxin B producers, and aflatoxin B and G producers, respectively, while in peanut kernel isolates were 44, 44, and 12 %. Three different A. section Flavi species were identified from peanut kernels: A. flavus, A. parasiticus, and A. pseudocaelatus. The mean aflatoxin concentration in peanut kernels was 42, 316, and 695.5 μg/kg in samples under no stress, mild stress, and severe stress conditions, respectively. Considering the harvest time, the mean aflatoxin concentration was 9.9, 334.3, and 614.2 μg/kg in samples harvested two weeks earlier, one week earlier, and in ideal harvest, respectively. In conclusion, the early harvest proved to be a viable, cost-free alternative for controlling aflatoxin in the peanut pre-harvest, resulting in a safer product and a better quality for sale and economic gain.

Isolated from Lungs of Poultry (Gallus gallus) at the Mycology Laboratory, School of Veterinary Medicine, Universidad Nacional, Heredia, Costa Rica between 2008 and 2021 and Associated Factors

Aspergillosis is a disease caused by some species of the fungus Aspergillus, occurring in both mammals (including humans) and birds, the latter being the most susceptible group. Aspergillus must be considered a public health concern as it affects the poultry industry economically and is an occupational risk to its workers. A retrospective study of fungal isolates from the lungs of chickens (Gallus gallus), analyzed between 2008 and 2021 at the Mycology Laboratory, School of Veterinary Medicine, Universidad Nacional, Heredia, Costa Rica was performed to report the prevalence of Aspergillus spp. in poultry farms in Costa Rica and their associated factors. A total of 1113 cases were received, of which 31% (n = 392; 95% CI: 28.3−33.7) were positive for fungal isolation. Aspergillus was the most frequently detected genus, and the most frequent sections were Fumigati (n = 197/392, 50.3%), Flavi (n = 90/392, 22.9%), and Nigri (n = 50/392, 12.7%). Significant effects (p < 0.05) related to the year, geographical origin, purpose, and age were identified in relation to the Aspergillus infection. The identified factors are explained by climatic variations in the tropics and the particularities of the birds. Future research including molecular characterization and antifungal susceptibility tests in animals, humans, and the environment, are needed to better understand the risks of the diseases caused by those fungi in this country.

Low-cost, specific PCR assays to identify the main aflatoxigenic species of Aspergillus section Flavi

Aflatoxins are fungal metabolites that are present as contaminants in food globally. Most aflatoxigenic species belong to Aspergillus section Flavi, and the main ones are grouped in the A. flavus clade, where many cryptic species that are difficult to discriminate are found. In this study, we investigated inter- and intraspecific diversity of the A. flavus clade to develop low-cost, species-specific PCR assays for identifying aflatoxigenic species. A total of 269 sequences of the second largest subunit of RNA polymerase II (RPB2) locus were retrieved from GenBank, and primer pairs were designed using data mining to identify A. flavus, A. parasiticus, and A. novoparasiticus. Species-specific amplicons of approximately 620, 350, and 860 bp enabled identification of target species as A. flavus, A. parasiticus, and A. novoparasiticus, respectively.

Mixed Etiology COVID-19 Associated Pulmonary Aspergillosis (CAPA)-A Case Report and Brief Review of the Literature

The SARS-CoV-2 pandemic has proved to be a significant risk addition for invasive infections with Aspergillus. Even though there are plenty of data about the COVID-19-associated pulmonary aspergillosis (CAPA), especially involving Aspergillus fumigatus, recent studies are presenting cases of CAPA involving more than one species of Aspergillus. We report the first case of a SARS-CoV-2 patient associating co-infection with, most likely, Aspergillus section Fumigati and Aspergillus section Flavi from Romania, and we review the existing medical literature in order to shed light upon mixed etiology cases of CAPA. Since mortality remains high in these cases, there is an acute need for more information about the interaction between SARS-CoV-2 and Aspergillus spp., and the therapies for CAPA. The emerging number of cases and the high mortality rate must be considered an incentive for future research.

Differentiation of Aspergillus flavus from Aspergillus oryzae Targeting the cyp51A Gene

Aspergillus flavus is one of the most important agents of invasive and non-invasive aspergillosis, especially in tropical and subtropical regions of the world, including Iran. Aspergillus oryzae is closely related to A. flavus, and it is known for its economic importance in traditional fermentation industries. Reports of infection due to A. oryzae are scarce. Several studies reported that differentiating these two species in clinical laboratories is not possible using MALDI-TOF or by targeting fungal barcode genes, such as Internal Transcribed Spacer (ITS) and β-tubulin (benA). The species-level identification of causative agents and the determination of antifungal susceptibility patterns can play significant roles in the outcome of aspergillosis. Here, we aimed to investigate the discriminatory potential of cyp51A PCR-sequencing versus that of the ITS, benA and calmodulin (CaM) genes for the differentiation of A. flavus from A. oryzae. In a prospective study investigating the molecular epidemiology of A. flavus in Iran between 2008 and 2018, out of 200 clinical isolates of A. flavus, 10 isolates showed >99% similarity to both A. flavus and A. oryzae. Overall, the ITS, β-tubulin and CaM genes did not fulfil the criteria for differentiating these 10 isolates. However, the cyp51A gene showed promising results, which warrants further studies using a larger set of isolates from more diverse epidemiological regions of the world.

Mass Spectrometry-Based Network Analysis Reveals New Insights Into the Chemodiversity of 28 Species in Aspergillus section Flavi

Aspergillus section Flavi includes some of the most famous mycotoxin producing filamentous fungi known to mankind. In recent years a number of new species have been included in section Flavi, however these species have been much less studied from a chemical point of view. In this study, we explored one representative strain of a total of 28 fungal species in section Flavi by systematically evaluating the relationship between taxonomy and secondary metabolites with LC-MS/MS analysis for the first time and dereplication through an in-house database and the Global Natural Product Social Molecular Networking (GNPS) platform. This approach allowed rapid identification of two new cyclopiazonic acid producers (A. alliaceus and A. arachidicola) and two new tenuazonic acid producers (A. arachidicola and A. leporis). Moreover, for the first time we report species from section Flavi to produce fumifungin and sphingofungins B-D. Altogether, this study emphasizes that the chemical diversity of species in genus Aspergillus section Flavi is larger than previously recognized, and especially that understudied species are prolific producers of important mycotoxins such as fumi- and sphingofungins not previously reported from this section. Furthermore, our work demonstrates Global Natural Product Social (GNPS) Molecular Networking as a powerful tool for large-scale chemotaxonomic analysis of closely related species in filamentous fungi.

Aspergillosis in albatrosses

Aspergillosis is a respiratory fungal disease of importance in captive marine birds. The aim of this study was to describe the occurrence of aspergillosis in Thalassarche melanophris during rehabilitation events and to identify the etiological agent. All the albatrosses that were received for rehabilitation and died within a 2-year period were included in the study. The proportionate mortality rate caused by aspergillosis was 21.4% (3/14). One of the etiological agents was Aspergillus flavus/oryzae lineage, and the other was A. fumigatus sensu stricto. Our study suggests that aspergillosis can act as a limiting factor in the rehabilitation of albatrosses.

Effects of chlorpyrifos on growth and aflatoxin B1 production by Aspergillus section Flavi strains on maize-based medium and maize grains

Chlorpyrifos is one of the most used insecticides in agro-ecosystems and is repeatedly applied due to the increase in pest resistance, which leads to environmental accumulation. The aim of this work was to evaluate the effect of chlorpyrifos on growth and aflatoxin B₁ (AFB₁) production by four Aspergillus section Flavi strains, under different water conditions-a_W (0.93, 0.95 and 0.98)-on maize-based medium (MMEA) and maize grains supplied with 0.06 to 1.4 mmol/L of chlorpyrifos. MMEA plates were incubated at 18, 28, and 37 °C and plates with maize grains at 25 °C during 21 days. Chlorpyrifos stimulated the growth and AFB₁ production of non-target organisms, such as Aspergillus section Flavi strains, both at low (0.06 mmol/L) and at high concentrations (1.4 mmol/L) on MMEA and maize grains. Stimulation occurred over a wide range of temperature and a_w conditions. The toxin concentration produced by the two strains on MMEA at 18 °C increased when the concentration of chlorpyrifos also increased, being most significant at 0.6 mmol/L. In conclusion, the presence of chlorpyrifos should be considered as a factor, together with environmental conditions, for the development of effective production practices of maize grains, in order to avoid fungal growth and AFB₁ production, to prevent both economic losses and risks to human and animal health.

Copper-Chitosan Nanocomposite Hydrogels Against Aflatoxigenic Aspergillus flavus from Dairy Cattle Feed

The integration of copper nanoparticles as antifungal agents in polymeric matrices to produce copper polymer nanocomposites has shown excellent results in preventing the growth of a wide variety of toxigenic fungi. Copper-chitosan nanocomposite-based chitosan hydrogels (Cu-Chit/NCs hydrogel) were prepared using a metal vapor synthesis (MVS) and the resulting samples were described by transmission electron microscopy (TEM), X-ray fluorescence analysis (XRF), and small-angle X-ray scattering (SAXS). Aflatoxin-producing medium and VICAM aflatoxins tests were applied to evaluate their ability to produce aflatoxins through various strains of Aspergillus flavus associated with peanut meal and cotton seeds. Aflatoxin production capacity in four fungal media outlets revealed that 13 tested isolates were capable of producing both aflatoxin B1 and B2. Only 2 A. flavus isolates (Af11 and Af 20) fluoresced under UV light in the A. flavus and parasiticus Agar (AFPA) medium. PCR was completed using two specific primers targeting aflP and aflA genes involved in the synthetic track of aflatoxin. Nevertheless, the existence of aflP and aflA genes indicated some correlation with the development of aflatoxin. A unique DNA fragment of the expected 236 bp and 412 bp bands for aflP and aflA genes in A. flavus isolates, although non-PCR fragments have been observed in many other Aspergillus species. This study shows the antifungal activity of Cu-Chit/NCs hydrogels against aflatoxigenic strains of A. flavus. Our results reveal that the antifungal activity of nanocomposites in vitro can be effective depending on the type of fungal strain and nanocomposite concentration. SDS-PAGE and native proteins explain the apparent response of cellular proteins in the presence of Cu-Chit/NCs hydrogels. A. flavus treated with a high concentration of Cu-Chit/NCs hydrogels that can decrease or produce certain types of proteins. Cu-Chit/NCs hydrogel decreases the effect of G6DP isozyme while not affecting the activity of peroxidase isozymes in tested isolates. Additionally, microscopic measurements of scanning electron microscopy (SEM) showed damage to the fungal cell membranes. Cu-Chit/NCS hydrogel is an innovative nano-biopesticide produced by MVS is employed in food and feed to induce plant defense against toxigenic fungi.

Molecular Analysis of S-morphology Aflatoxin Producers From the United States Reveals Previously Unknown Diversity and Two New Taxa

Aflatoxins are highly toxic carcinogens that detrimentally influence profitability of agriculture and the health of humans and domestic animals. Several phylogenetically distinct fungi within Aspergillus section Flavi have S-morphology (average sclerotial size < 400 μm), and consistently produce high concentrations of aflatoxins in crops. S-morphology fungi have been implicated as important etiologic agents of aflatoxin contamination in the United States (US), but little is known about the diversity of these fungi. The current study characterized S-morphology fungi (n = 494) collected between 2002 and 2017, from soil and maize samples, in US regions where aflatoxin contamination is a perennial problem. Phylogenetic analyses based on sequences of the calmodulin (1.9 kb) and nitrate reductase (2.1 kb) genes resolved S-morphology isolates from the US into four distinct clades: (1) Aspergillus flavus S-morphotype (89.7%); (2) Aspergillus agricola sp. nov. (2.4%); (3) Aspergillus texensis (2.2%); and (4) Aspergillus toxicus sp. nov. (5.7%). All four S-morphology species produced high concentrations of aflatoxins in maize at 25, 30, and 35°C, but only the A. flavus S-morphotype produced unacceptable aflatoxin concentrations at 40°C. Genetic typing of A. flavus S isolates using 17 simple sequence repeat markers revealed high genetic diversity, with 202 haplotypes from 443 isolates. Knowledge of the occurrence of distinct species and haplotypes of S-morphology fungi that are highly aflatoxigenic under a range of environmental conditions may provide insights into the etiology, epidemiology, and management of aflatoxin contamination in North America.

Interaction of Aspergillus flavus and A. parasiticus with Salmonella spp. isolated from peanuts

Although Aspergillus flavus and Aspergillus parasiticus are the main microorganisms of concern in peanuts, due to aflatoxin contamination, several Salmonella outbreaks from this product have been reported over the last ten decades. Thus, it is important to understand the relationship between microorganisms to predict, manage and estimate the diversity in the peanut supply chain. The purpose of this study was to evaluate aflatoxin production during the co-cultivation of Aspergillus section Flavi and Salmonella both isolated from peanuts. Three strains of A. section Flavi: A. flavus producing aflatoxin B, A. flavus non-producing aflatoxin and A. parasiticus producing aflatoxin B and G were co-cultivated with seven serotypes of Salmonella of which six were isolated from the peanut supply chain (S. Muenster, S. Miami, S. Glostrup, S. Javiana, S. Oranienburg and S. Yoruba) and one was S. Typhimurium ATCC 14028. First of all, each Salmonella strain was inoculated by pour plate (ca. 5 log cfu/mL) in PDA (potato dextrose agar). Then, each pre-cultured fungus was inoculated in the center of the petri dish. The plates were incubated at 30 °C and the fungal colony diameter was measured once a day for 7 days. As a control each Aspergillus strain was cultivated in the absence of Salmonella culture. All three strains of Aspergillus with absence of Salmonella (control) reached the maximum colony diameter and their growth rate was influenced when co-cultivated (p < 0.05) with all Salmonella serotypes tested. The maximum inhibition in the colony diameter was 20% for A. flavus aflatoxin B producer and A. parasiticus, and 18% for A. flavus non- aflatoxin producer when cultivated with Salmonella. However, no significant difference (p < 0.05) in reduction of colony diameter was observed among the Salmonella serotypes. Aflatoxin production was determined previously, by using the agar plug technique on thin layer chromatography (TLC). The production of aflatoxin G by A. parasiticus in co-cultivation with Salmonella was not observed. On the other hand, A. flavus preserved their characteristics of aflatoxin B production. The quantification of aflatoxin reduction by Salmonella interaction was evaluated using HPLC method. There was a maximum reduction of aflatoxin production of 88.7% and 72.9% in A. flavus and A. parasiticus, respectively, when cultivated with Salmonella. These results indicate that some serotypes of Salmonella may interfere with aflatoxin production and fungal growth of A. flavus and A. parasiticus in the peanut supply chain.

Toxigenicity and phylogeny of Aspergillus section Flavi in poultry feed in Iran

Background and Purpose

This study was conducted to evaluate the presence of aflatoxigenic strains and level of aflatoxin in poultry feed. Aflatoxigenic strains were investigated in corn and soybean meal as the ingredients of poultry feed, as well as in two types of commercial feed, namely pellet and mash. The gene sequencing was performed to identify the species of Aspergillus section Flavi.

Materials and Methods

All samples were randomly collected from feed storage silos located in Iran in 2018. The samples were cultured on specialized media for 2 weeks at 28ºC. Identification of Aspergillus section Flavi isolates was based on macro- and microscopic morphological criteria and molecular analysis. The thin-layer chromatography (TLC) was applied to confirm the aflatoxigenic isolates. In addition, the level of aflatoxin B₁ (AFB₁) produced by these isolates was determined by high-performance liquid chromatography. The strains were subjected to sequence analysis, and Bt2 PCR products were purified by the QIAquick PCR purification kit. At the final stage, the phylogenetic tree was built.

Results

Among 54 isolates identified as Aspergillus section Flavi, 20 (37%) isolates were found to produce aflatoxin at a range of 11.28±1.18 to 2239.92±92.26 µg/g fungal dry weight. The aflatoxigenic isolates had the frequencies of 45%, 40%, 10%, and 5% in the corn, pellet, soybean meal, and mash samples, respectively. Furthermore, the mean concentrations of AFB₁ were significantly higher in the corn samples (707.04±39.05) than that of other poultry feed samples (P<0.05). A total of 34 (63%) isolates were detected as non-aflatoxigenic on the yeast extract-sucrose broth in TLC analysis. The toxigenic isolates produced the highest (2232.62±55.49) and lowest (11.28±1.18) levels of AFB₁ in the corn samples, compared to other feedstuffs. Furthermore, the mean level of AFB₁ in mash product was 554.09±10.36 µg/g, compared to a mean level of 229.22±11.09 µg/g in pellets. The isolates were randomly selected, sequenced, and then analyzed. Subsequently, the phylogenetic tree of Aspergillus section Flavi was plotted.

Conclusion

The process of converting raw ingredients to compound poultry feed is more hazardous when there is not enough time and temperature provided to eliminate aflatoxigenic isolates. Therefore, Aspergillus section Flavi in poultry feed can pose a threat to the poultry industry and poultry products, thereby affecting the health status of humans. Unprocessed/processed materials, such as corns and pelleted feed, need further monitoring, especially when conditions are not optimal for destroying the fungus.

Aspergillus section Flavi and Aflatoxins: Occurrence, Detection, and Identification in Raw Peanuts and Peanut-Based Products Along the Supply Chain

Aflatoxin contamination in foods is a global concern as they are carcinogenic, teratogenic and mutagenic compounds. The aflatoxin-producing fungi, mainly from the Aspergillus section Flavi, are ubiquitous in nature and readily contaminate various food commodities, thereby affecting human's health. The incidence of aflatoxigenic Aspergillus spp. and aflatoxins in various types of food, especially raw peanuts and peanut-based products along the supply chain has been a concern particularly in countries having tropical and sub-tropical climate, including Malaysia. These climatic conditions naturally support the growth of Aspergillus section Flavi, especially A. flavus, particularly when raw peanuts and peanut-based products are stored under inappropriate conditions. Peanut supply chain generally consists of several major stakeholders which include the producers, collectors, exporters, importers, manufacturers, retailers and finally, the consumers. A thorough examination of the processes along the supply chain reveals that Aspergillus section Flavi and aflatoxins could occur at any step along the chain, from farm to table. Thus, this review aims to give an overview on the prevalence of Aspergillus section Flavi and the occurrence of aflatoxins in raw peanuts and peanut-based products, the impact of aflatoxins on global trade, and aflatoxin management in peanuts with a special focus on peanut supply chain in Malaysia. Furthermore, aflatoxin detection and quantification methods as well as the identification of Aspergillus section Flavi are also reviewed herein. This review could help to shed light to the researchers, peanut stakeholders and consumers on the risk of aflatoxin contamination in peanuts along the supply chain.

Aflatoxin-producing fungi associated with pre-harvest maize contamination in Uganda

Maize is an important staple crop for the majority of the population in Uganda. However, in tropical and subtropical climates, maize is frequently contaminated with aflatoxins, a group of cancer-causing and immuno-suppressive mycotoxins produced by Aspergillus section Flavi fungi. In Uganda, there is limited knowledge about the causal agents of aflatoxin contamination. The current study determined both the aflatoxin levels in pre-harvest maize across Uganda and the structures of communities of aflatoxin-producing fungi associated with the maize. A total of 256 pre-harvest maize samples were collected from 23 major maize-growing districts in eight agro-ecological zones (AEZ). Maize aflatoxin content ranged from 0 to 3760 ng/g although only around 5% for Ugandan thresholds. For EU it is about 16% of the samples contained aflatoxin concentrations above tolerance thresholds. A total of 3105 Aspergillus section Flavi isolates were recovered and these were dominated by the A. flavus L morphotype (89.4%). Densities of aflatoxin-producing fungi were negatively correlated with elevation. Farming systems and climatic conditions of the AEZ are thought to have influenced communities' structure composition. Fungi from different AEZ varied significantly in aflatoxin-producing abilities and several atoxigenic genotypes were identified. The extremely high aflatoxin concentrations detected in some of the studied regions indicate that management strategies should be urgently designed for use at the pre-harvest stage. Atoxigenic genotypes detected across Uganda could serve as aflatoxin biocontrol agents to reduce crop contamination from fields conditions and throughout the maize value chain.

Biocontrol Strains Differentially Shift the Genetic Structure of Indigenous Soil Populations of Aspergillus flavus

Biocontrol using non-aflatoxigenic strains of Aspergillus flavus has the greatest potential to mitigate aflatoxin contamination in agricultural produce. However, factors that influence the efficacy of biocontrol agents in reducing aflatoxin accumulation under field conditions are not well-understood. Shifts in the genetic structure of indigenous soil populations of A. flavus following application of biocontrol products Afla-Guard and AF36 were investigated to determine how these changes can influence the efficacy of biocontrol strains in reducing aflatoxin contamination. Soil samples were collected from maize fields in Alabama, Georgia, and North Carolina in 2012 and 2013 to determine changes in the population genetic structure of A. flavus in the soil following application of the biocontrol strains. A. flavus L was the most dominant species of Aspergillus section Flavi with a frequency ranging from 61 to 100%, followed by Aspergillus parasiticus that had a frequency of <35%. The frequency of A. flavus L increased, while that of A. parasiticus decreased after application of biocontrol strains. A total of 112 multilocus haplotypes (MLHs) were inferred from 1,282 isolates of A. flavus L using multilocus sequence typing of the trpC, mfs, and AF17 loci. A. flavus individuals belonging to the Afla-Guard MLH in the IB lineage were the most dominant before and after application of biocontrol strains, while individuals of the AF36 MLH in the IC lineage were either recovered in very low frequencies or not recovered at harvest. There were no significant (P > 0.05) differences in the frequency of individuals with MAT1-1 and MAT1-2 for clone-corrected MLH data, an indication of a recombining population resulting from sexual reproduction. Population mean mutation rates were not different across temporal and spatial scales indicating that mutation alone is not a driving force in observed multilocus sequence diversity. Clustering based on principal component analysis identified two distinct evolutionary lineages (IB and IC) across all three states. Additionally, patristic distance analysis revealed phylogenetic incongruency among single locus phylogenies which suggests ongoing genetic exchange and recombination. Levels of aflatoxin accumulation were very low except in North Carolina in 2012, where aflatoxin levels were significantly (P < 0.05) lower in grain from treated compared to untreated plots. Phylogenetic analysis showed that Afla-Guard was more effective than AF36 in shifting the indigenous soil populations of A. flavus toward the non-toxigenic or low aflatoxin producing IB lineage. These results suggest that Afla-Guard, which matches the genetic and ecological structure of indigenous soil populations of A. flavus in Alabama, Georgia, and North Carolina, is likely to be more effective in reducing aflatoxin accumulation and will also persist longer in the soil than AF36 in the southeastern United States.

Occurrence and Identification of Aspergillus Section Flavi in the Context of the Emergence of Aflatoxins in French Maize

Aflatoxins (AFs) are secondary metabolites produced by Aspergillus section Flavi during their development, particularly in maize. It is widely accepted that AFB1 is a major contaminant in regions where hot climate conditions favor the development of aflatoxigenic species. Global warming could lead to the appearance of AFs in maize produced in Europe. This was the case in 2015, in France, when the exceptionally hot and dry climatic conditions were favorable for AF production. Our survey revealed AF contamination of 6% (n = 114) of maize field samples and of 15% (n = 81) of maize silo samples analyzed. To understand the origin of the contamination, we characterized the mycoflora in contaminated samples and in samples produced in the same geographic and climatic conditions but with no AFs. A special focus was placed on Aspergillus section Flavi. A total of 67 strains of Aspergillus section Flavi were isolated from the samples. As expected, the strains were observed in all AF+ samples and, remarkably, also in almost 40% of AF- samples, demonstrating the presence of these potent toxin producers in fields in France. A. flavus was the most frequent species of the section Flavi (69% of the strains). But surprisingly, A. parasiticus was also a frequent contaminant (28% of the strains), mostly isolated from AF+ samples. This finding is in agreement with the presence of AFG in most of those samples.

Aspergillus korhogoensis, a Novel Aflatoxin Producing Species from the Côte d'Ivoire

Several strains of a new aflatoxigenic species of Aspergillus, A. korhogoensis, were isolated in the course of a screening study involving species from section Flavi found contaminating peanuts (Arachis hypogaea) and peanut paste in the Côte d'Ivoire. Based on examination of four isolates, this new species is described using a polyphasic approach. A concatenated alignment comprised of nine genes (ITS, benA, cmdA, mcm7, amdS, rpb1, preB, ppgA, and preA) was subjected to phylogenetic analysis, and resulted in all four strains being inferred as a distinct clade. Characterization of mating type for each strain revealed A. korhogoensis as a heterothallic species, since three isolates exhibited a singular MAT1-1 locus and one isolate exhibited a singular MAT1-2 locus. Morphological and physiological characterizations were also performed based on their growth on various types of media. Their respective extrolite profiles were characterized using LC/HRMS, and showed that this new species is capable of producing B- and G-aflatoxins, aspergillic acid, cyclopiazonic acid, aflavarins, and asparasones, as well as other metabolites. Altogether, our results confirm the monophyly of A. korhogoensis, and strengthen its position in the A. flavus clade, as the sister taxon of A. parvisclerotigenus.

Assessment of growth of Aspergillus spp. from agricultural soils in the presence of glyphosate

Agriculture is one of the bases of the Argentine economy. Glyphosate is undoubtedly one of the most important herbicides used. The increasing consumption and the efficiency of glyphosate-based herbicides have encouraged several studies on their persistence in soils, their effects on soil microbiota and their degradation processes. Fungi have been reported as being the main herbicide-degrading microorganisms as well as the most tolerant to environmental stress conditions. This study evaluated the growth performance of Aspergillus section Flavi and Aspergillus niger aggregate strains on Czapek Dox media supplied with a commercial glyphosate formulation as sole source of carbon (CZC), phosphorus (CZP) or nitrogen (CZN). Six Aspergillus spp. strains were evaluated. Each medium was stab-inoculated with fungal spores from 7-day old cultures. Two measures of colony radii were taken daily. All of the Aspergillus section Flavi strains showed a significant increase (from 24 to 44%) in growth rate on the CZN medium, as compared to controls. The A. niger aggregate strains exhibited the same behavioral pattern under all the conditions tested, except on the CZN medium. Velutinous or slightly floccose colonies with abundant sporulation were observed on CZP. Moreover, the colonies produced sparse sporulation on CZC or CZN media, being their appearances completely different from those on the CZP medium. This study establishes that A. section Flavi and A. niger aggregate strains can grow in vitro in the presence of glyphosate, especially when it is used as a sole source of phosphorus or nitrogen.

Aflatoxin contamination of groundnut and maize in Zambia: observed and potential concentrations

AIMS

The aims of the study were to quantify aflatoxins, the potent carcinogens associated with stunting and immune suppression, in maize and groundnut across Zambia's three agroecologies and to determine the vulnerability to aflatoxin increases after purchase.

METHODS AND RESULTS

Aflatoxin concentrations were determined for 334 maize and groundnut samples from 27 districts using lateral-flow immunochromatography. Seventeen per cent of crops from markets contained aflatoxin concentrations above allowable levels in Zambia (10 μg kg-1 ). Proportions of crops unsafe for human consumption differed significantly (P < 0·001) among agroecologies with more contamination (38%) in the warmest (Agroecology I) and the least (8%) in cool, wet Agroecology III. Aflatoxin in groundnut (39 μg kg-1 ) and maize (16 μg kg-1 ) differed (P = 0·032). Poor storage (31°C, 100% RH, 1 week) increased aflatoxin in safe crops by over 1000-fold in both maize and groundnut. The L morphotype of Aspergillus flavus was negatively correlated with postharvest increases in groundnut.

CONCLUSIONS

Aflatoxins are common in Zambia's food staples with proportions of unsafe crops dependent on agroecology. Fungal community structure influences contamination suggesting Zambia would benefit from biocontrol with atoxigenic A. flavus.

SIGNIFICANCE AND IMPACT OF THE STUDY

Aflatoxin contamination across the three agroecologies of Zambia is detailed and the case for aflatoxin management with atoxigenic biocontrol agents provided. The first method for evaluating the potential for aflatoxin increase after purchase is presented.

Kinetics of aflatoxin degradation during peanut roasting

This study investigated aflatoxin degradation during peanut roasting. First, peanuts contaminated with three initial aflatoxin concentrations (35, 332 and 695μg/kg) were roasted at 180°C for up to 20min. The percentage of aflatoxin degradation after 20min were 55, 64 and 81% for peanuts contaminated with aflatoxin at 35, 332 and 695μg/kg, respectively. This difference was statistically significant (p<0.05), showing that initial concentration influences aflatoxin reduction. Thereafter, peanut samples contaminated with an initial aflatoxin concentration of 85μg/kg were roasted at 160, 180 and 200°C for 5, 10, 15, 20 and 25min, then residual concentrations of aflatoxin were determined. Roasting at 160, 180 and 200°C resulted in an aflatoxin reduction of 61.6, 83.6 and 89.7%, respectively. This study has provided quantitative data reinforcing the fact that roasting alone is not enough to control aflatoxins in peanuts.

The biodiversity of Aspergillus section Flavi and aflatoxins in the Brazilian peanut production chain

A total of 119 samples of peanut were collected throughout the peanut production chain in São Paulo State, Brazil. The peanut samples were directly plated for determination of percentages of infection and a polyphasic approach was used to identify Aspergillus section Flavi species. Further, the potential for aflatoxin production by the isolates was tested using the agar plug technique and the presence of aflatoxins in peanuts was assessed using an immunoaffinity column followed by quantification using HPLC with reverse phase column and fluorescence detection. The limit of detection and quantification were 0.05 and 0.17μg/kg for total aflatoxins, respectively. Four species of Aspergillus section Flavi were isolated: A. caelatus (11), A. flavus (515), A. parasiticus (17) and A. tamarii (13). All isolates of A. parasiticus were able to produce aflatoxin B and G whereas aflatoxin B was produced by 50% of A. flavus isolates. Aflatoxins were found in 12 samples at concentrations ranging from 0.3 to 100μg/kg. The data reported in this study add information on the occurrence and biodiversity of fungi in peanuts at several stages of the production chain. The occurrence of aflatoxins is also of major relevance for continuous monitoring and assessment of likely exposure of consumers to aflatoxins through consumption of peanuts.

Brazil nuts are subject to infection with B and G aflatoxin-producing fungus, Aspergillus pseudonomius

The exploitation of the Brazil nut is one of the most important activities of the extractive communities of the Amazon rainforest. However, its commercialization can be affected by the presence of aflatoxins produced by fungi, namely Aspergillus section Flavi. In the present study, we investigated a collection of Aspergillus nomius strains isolated from Brazil nuts using different approaches, including morphological characters, RAPD and AFLP profiles, partial β-tubulin and calmodulin nucleotide sequences, aflatoxin patterns, as well as tolerance to low water activity in cultured media. Results showed that most of the isolates do belong to A. nomius species, but a few were re-identified as Aspergillus pseudonomius, a very recently described species. The results of the analyses of molecular variance, as well as the high pairwise FST values between A. nomius and A. pseudonomius suggested the isolation between these two species and the inexistence of gene flow. Fixed interspecific nucleotide polymorphisms at β-tubulin and calmodulin loci are presented. All A. pseudonomius strains analyzed produced aflatoxins AFB1, AFB2, AFG1 and AFG2. This study contains the first-ever report on the occurrence in Brazil nuts of A. pseudonomius. The G-type aflatoxins and the mycotoxin tenuazonic acid are reported here for the first time in A. pseudonomius.

Antifungal impact of volatile fractions of Peumus boldus and Lippia turbinata on Aspergillus section Flavi and residual levels of these oils in irradiated peanut

To investigate the antifungal properties of essential oil (EO) vapors from boldo and poleo on Aspergillus section Flavi and the residual levels of the oils in peanut, irradiated peanuts conditioned at three water activities (0.98, 0.95, 0.93) were treated with 2 and 3 μL/g of boldo and 3 and 5 μL/g of poleo. EO treatments produced the greatest impact on fungal growth parameters, followed by oil concentrations and aW levels. The three main components in peanut exposed to oil vapors were piperitone oxide, α-terpinene and eucalyptol for boldo and β-caryophyllene epoxide, limonene and piperitenone for poleo. Residues of boldo and poleo EO were significantly decreased from 24.7 to 100% and from 26.6 to 99.7% at the end of the incubation period, respectively. The application of nontoxic boldo oil as fumigant in the control of Aspergillus section Flavi may represent a potential alternative antifungal treatment, without significant residues after 35 days.

Two new aflatoxin producing species, and an overview of Aspergillus section Flavi

Aspergillus subgenus Circumdati section Flavi includes species with usually biseriate conidial heads, in shades of yellow-green to brown, and dark sclerotia. Several species assigned to this section are either important mycotoxin producers including aflatoxins, cyclopiazonic acid, ochratoxins and kojic acid, or are used in oriental food fermentation processes and as hosts for heterologous gene expression. A polyphasic approach was applied using morphological characters, extrolite data and partial calmodulin, β-tubulin and ITS sequences to examine the evolutionary relationships within this section. The data indicate that Aspergillus section Flavi involves 22 species, which can be grouped into seven clades. Two new species, A. pseudocaelatus sp. nov. and A. pseudonomius sp. nov. have been discovered, and can be distinguished from other species in this section based on sequence data and extrolite profiles. Aspergillus pseudocaelatus is represented by a single isolate collected from Arachis burkartii leaf in Argentina, is closely related to the non-aflatoxin producing A. caelatus, and produces aflatoxins B & G, cyclopiazonic acid and kojic acid, while A. pseudonomius was isolated from insects and soil in the USA. This species is related to A. nomius, and produces aflatoxin B(1) (but not G-type aflatoxins), chrysogine and kojic acid. In order to prove the aflatoxin producing abilities of the isolates, phylogenetic analysis of three genes taking part in aflatoxin biosynthesis, including the transcriptional regulator aflR, norsolonic acid reductase and O-methyltransferase were also carried out. A detailed overview of the species accepted in Aspergillus section Flavi is presented.