Aflatoxin-producing Aspergillus Research Articles

Microbiome Evolution of Brewer’s Spent Grain and Spent Coffee Ground Solid Sidestreams Under Industrial Storage Conditions

Brewer’s spent grain (BSG) and spent coffee ground (SCG) are solid sidestreams from beverage production increasingly being upcycled into food, feed and other value-added products. These solid sidestreams are prone to microbial spoilage, negatively impacting their upcycling potential. Three samples each of BSG and SCG were obtained from generators and recycling facilities in Singapore, and their chemical, elemental, and microbial composition was characterized. The spoilage mechanisms were investigated during storage under anaerobic and aerobic conditions. Bacterial loads of sidestreams were low from craft brewery and café sources (<1 and 3.53 ± 0.03 log10 CFU/g) and high from recycling facilities (>6 log10 CFU/g). The microbiome of BSG from recycling facilities was dominated by Bacilli, and B. coagulans was identified as the most prevalent species. SCG from recycling facilities was dominated by lactic acid bacteria, with L. panis being the most prevalent species. Storage up to 14 days under anaerobic conditions led to further bacterial proliferation mainly by Bacilli, lactic acid bacteria, and acetic acid bacteria, while aerobic storage led to extensive fungal contamination, including potential aflatoxin-producing Aspergillus flavus. The results shed light on the spoilage mechanisms, while highlighting the short shelf-life and food safety risks of BSG and SCG to inform valorization strategies.

Effect of lactic acid bacteria inoculation on the aflatoxin B1 contamination and the diversity of yeast communities in Aspergillus flavus-contaminated experimental corn silage

AbstractThe present work aimed to study the yeast communities of whole crop corn silages (CS) that were previously contaminated with aflatoxin-producing Aspergillus flavus (CSCA). In addition, the effect of lactic acid bacterium (LAB) inoculation on the aflatoxin B1 (AFB1) content, genotoxicity, yeast load, and diversity of yeast communities were also investigated. In A. flavus contaminated silages, after two months, the AFB1 content was 40% lower with LAB inoculation, also a lower level of genotoxicity was determined. The number of yeasts cultured from the initial mixture of chopped whole crop corn was 4.8 × 107 CFU g−1 wet mass, while only 2.4 × 106 CFU g−1 from the CSCA and 7.1 × 105 CFU g−1 from the LAB-inoculated CSCA could be cultured. Based on 144 randomly isolated strains, the yeast community of the initial mixture consisted of 8 species. In contrast, the yeast community of CSCA consisted only of 4 species determined by 132 randomly selected isolates. LAB-inoculated CSCA consisted also of 4 species based on 158 randomly isolated strains. Saccharomyces cerevisiae and Pichia kudriavzevii proved to be predominant in the CSCA, while S. cerevisiae and Meyerozyma guilliermondii were the most abundant in the LAB-inoculated CSCA. The species richness was also confirmed by alpha diversity values (1.827, 1.188, and 1.123 as Shannon's indices for CS, CSCA, and LAB-inoculated CSCA, respectively). In response to LAB inoculation, the species diversity decreased considerably.

Investigating safe storage conditions to mitigate aflatoxin contamination in rice

Mold contamination, especially with aflatoxin-producing Aspergillus species, poses a notable issue for rice, particularly in ready-to-eat (RTE) items, turning them inedible for both humans and animals due to the possible presence of aflatoxins (AFs). Understanding accumulation of the molds and their resulting toxic metabolites is critical in designing quality control strategies in the production of RTE rice-based products such as germinated instant rice, extruded rice cakes and crispies, rice-derived malted beer and flour. There is no clear understanding of the growth of A. flavus and AF accumulation on various fractions of hybrid rice cultivars utilized in the manufacture of the RTE rice-derived food products. In the present work, different experiments were conducted to identify the extent to which temperature (20°C, 25°C, and 30°C), relative humidity (RH) (75%, 85%, and 95%), storage period, storage moisture content (MC), and initial spore concentration impacted the growth of AF-producing A. flavus NRRL 3357. The study also examined how these factors affected ergosterol content and aflatoxin B1 (AFB1) production in different hybrid rice fractions including rough, brown, and milled rice, at different MCs (12%, 15%, and 18% w.b.). The samples, both autoclaved and non-autoclaved rice fractions, were inoculated with different A. flavus spore concentrations (1 × 104 and 1 × 106 spores/mL) and incubated at different temperatures and RHs. A. flavus plate count, ergosterol and AFB1 production were measured over time for up to 60 days. The maximum A. flavus growth was observed in brown rice (autoclaved) at 30°C and 95% RH. Brown rice fraction (non-autoclaved) had the highest AFB1 concentration (9.20 μg/g) which was determined after 15 days of incubation at 30°C and 75% RH. Aflatoxin B1 concentration in brown rice (non-autoclaved) fraction inoculated with the highest concentration of A. flavus and stored at 30°C and 95% RH initially increased after 20 days and then decreased towards the end of the storage period. The findings from this research provide important data related to the growth behavior of A. flavus on various rice fractions. The results contribute to understanding of the safety of RTE foods derived from various fractions of rice that is utilized by the food industry.

Impact of conservation farming practices on Aspergillus population density, peanut aflatoxin level, and exposure risk in Zambia

Aflatoxin contamination in peanuts (Arachis hypogaea L.) by aflatoxin-producing Aspergillus spp. is a serious problem worldwide affecting human health and restricting trade. Recently, conservation agriculture practices such as minimum tillage, crop rotation, soil surface cover, intercropping, and planting in basins alongside trees that enhance soil fertility, have been introduced in Zambia as tools to conserve soil moisture, increase peanut yield, and reduce the risk of aflatoxin contamination. However, a limited understanding exists of the impact of conservation agriculture on Aspergillus population densities in the soil and aflatoxin concentrations in crops grown under conservation agriculture. This study assessed the impact of conservation agriculture on (i) Aspergillus communities profile in soil cropped to peanuts, (ii) peanut aflatoxin contamination levels, and (iii) influences of the practices on liver cancer risks as a result of consuming peanuts grown in basins, peanuts grown in basins in farms having Gliricidia sepium trees (agroforestry), and peanuts grown on ridges (conventional tillage). Densities of Aspergillus spp. in soils ranged from 10 to 7,400 CFU/g (mean = 295 CFU/g). The densities differed among farming techniques (p = 0.0011) with conventional tillage (357 CFU/g) supporting higher densities than agroforestry (296 CFU/g) and peanuts grown in basins (230 CFU/g). Aspergillus communities were dominated by fungi with S morphology (55%; which is composed of several morphologically similar species), followed by A. parasiticus (34%), and the L morphotype of A. flavus (11%). Over 60% of the peanut samples were contaminated but there were no differences among farming techniques. Mean aflatoxin contents in peanuts were 110, 99, and 87, μg/kg for agroforestry, conventional tillage, and peanuts grown in basins, respectively. Probable daily aflatoxin intake ranged from 12.7 to 767.1 ng/kg body weight/d, depending on the age of consumers. The estimated liver cancer risk due to consumption of raw peanuts (0.334 to 20.128 cases/100,000 persons/year) was highest among children below 5 years and least for young adults. The results showed that growing peanuts in basins has the potential to reduce Aspergillus populations in soil. Possibly, planting in basins and agroforestry had minimal effect on water runoff and did not support sufficient moisture retention in the soil to reduce Aspergillus spp. densities and aflatoxin accumulation in the peanuts. Thus, more research is needed to improve the effectiveness of peanut cultivation in basins in shaping the Aspergillus species profiles for ultimately reducing aflatoxin in peanuts to safe levels. Given the high exposure of Zambia’s population, especially children, and that contaminated food is the major source of exposure, it is essential that appropriate technical, policy and institutional measures are promoted for aflatoxin mitigation in Zambia.

Simultaneous detection of mycotoxigenic Aspergillus species of sections Circumdati and Flavi using multiplex digital PCR.

Populations of ochratoxin-producing Aspergillus section Circumdati species and aflatoxin-producing Aspergillus section Flavi species frequently coexist in soil and are the main sources of mycotoxin contamination of tree nuts. Identification of mycotoxigenic Aspergillus species in these sections is difficult using traditional isolation and culture methods. We developed a multiplex digital PCR (dPCR) assay to detect and quantify Aspergillus ochraceus, Aspergillus westerdijkiae, and Aspergillus steynii (section Circumdati), as well as Aspergillus flavus and Aspergillus parasiticus (section Flavi), in environmental samples based on species-specific calmodulin gene sequences. Relative quantification of each species by dPCR of mixed-species templates correlated with corresponding DNA input ratios. Target species could be detected in soil inoculated with conidia from each species. Non-target species of sections Circumdati, Flavi, and Nigri were generally not detectable using this dPCR method. Detected non-target species (Aspergillus fresenii, Aspergillus melleus, Aspergillus sclerotiorum, and Aspergillus subramanianii) were discernible from A. ochraceus in dual-template dPCR reactions based on differential fluorescence intensity.

Antifungal and Antiaflatoxigenic Activities of Massoia Essential Oil and C10 Massoia Lactone against Aflatoxin-Producing Aspergillus flavus.

Fungal infection and mycotoxin contamination are major hazards to the safe storage and distribution of foods and feeds consumed by humans and livestock. This study investigated the antifungal and antiaflatoxigenic activities of massoia essential oil (MEO) and its major constituent, C10 massoia lactone (C10), against aflatoxin B (AFB)-producing Aspergillus flavus ATCC 22546. Their antifungal activities were evaluated using a disc diffusion assay, agar dilution method, and a mycelial growth inhibition assay with the AFB analysis using liquid chromatography triple quadrupole mass spectrometry. MEO and C10 exhibited similar antifungal and antiaflatoxigenic activities against A. flavus. C10 was a primary constituent in MEO and represented up to 45.1% of total peak areas analyzed by gas chromatography-mass spectrometry, indicating that C10 is a major compound contributing to the antifungal and antiaflatoxigenic activities of MEO. Interestingly, these two materials increased AFB production in A. flavus by upregulating the expression of most genes related to AFB biosynthesis by 3- to 60-fold. Overall, MEO and C10 could be suitable candidates as natural preservatives to control fungal infection and mycotoxin contamination in foods and feeds as Generally Recognized As Safe (GRAS) in the Flavor and Extract Manufacturers Association of the United States (FEMA), and MEO is a more suitable substance than C10 because of its wider range of uses and higher allowed concentration than C10.

Correlation between Aspergillus flavus fungal biomass and aflatoxin contamination in harvested maize: insights from Kenya and Tanzania

Controlling the occurrence of aflatoxins in foods must be accompanied by managing the fungi responsible for their production. The abundance and diversity of aflatoxin-producing Aspergillus flavus are responsible for the accumulation of these toxins in crops, posing a persistent threat to public health and the economy in tropical developing countries. A study was conducted to investigate the occurrence and level of A. flavus and relate them to aflatoxin levels in maize in Kenya and Tanzania. A total of 786 maize samples were collected during harvesting in selected areas of the two countries for analysis. The fungal abundance in the samples was measured as the amount of fungal DNA relative to maize DNA. This was accomplished by quantifying the fungal DNA using qPCR, targeting the internal transcribed spacer (ITS) gene, while the maize DNA was quantified through the alpha-tubulin gene, the two genes known to be conserved. Aflatoxins were quantified using ultra-high performance liquid chromatography, coupled with ultra-high sensitivity, ultra-fast triple quadrupole tandem-mass spectrophotometer. A. flavus was detected in 88.5% of the 786 tested samples, and the average fungal load for these samples (expressed as the log host/pathogen ratio) was 5.53. Aflatoxin occurrence was positive in 31.9% of the samples, with an average level of 2.3 ± 0.643 ppb. The study established a positive relationship between the occurrence and level of aflatoxin B1 and the presence and biomass of A. flavus, which was statistically proven. These findings emphasize the need to place substantial attention on preharvest control of A. flavus in cereal fields as an effort to control the accumulation of aflatoxin B1 in foods.

Detection and Isolation of Aflatoxin-producing Aspergillus sp. in Chewing and Smokeless Tobacco by Microbial and Molecular Detection Methods and Its Influence on Hepatocellular Carcinomas in Wistar Rats

Detection and Isolation of Aflatoxin-producing Aspergillus sp. in Chewing and Smokeless Tobacco by Microbial and Molecular Detection Methods and Its Influence on Hepatocellular Carcinomas in Wistar Rats

Antifungal activity of potential probiotic Limosilactobacillus fermentum strains and their role against toxigenic aflatoxin-producing aspergilli

Two major aflatoxin-producing strains are Aspergillus flavus and Aspergillus niger. Probiotic bacteria have been identified as a potential means to fight aspergilli and reduce the availability of aflatoxin (AFs) as well as other food contaminants. In this study, the potential of ABRIIFBI-6 and ABRIIFBI-7 strains to inhibit the growth of aspergilli was investigated. Both strains survived in the simulated gastrointestinal conditions and inhibited the growth of Aspergillus significantly. Auto-aggregation ranged from 67.4 ± 1.9 for ABRIIFBI-6 to 75.8 ± 2.3% for ABRIIFBI-7, and hydrophobicity ranged from 57.3 ± 1.6 to 61.2 ± 1.4% for ABRIIFBI-6 and ranged from 51.2 ± 1.4 to 55.4 ± 1.8% for ABRIIFBI-7. The ranges of coaggregation with Staphylococcus aureus were 51.3 ± 1.7 and 52.4 ± 1.8% for ABRIIFBI-6 and ABRIIFBI-7, respectively, while coaggregation with Bacillus cereus was 57.9 ± 2.1 and 49.3 ± 1.9% for ABRIIFBI-6 and ABRIIFBI-7, respectively. Both strains indicated remarkable sensitivity to clinical antibiotics. According to the analysis of the identified potential probiotics, the findings of this study could significantly contribute to the understanding of the probiotic potential of LAB in dairy products in order to access their probiotic characterization for use as biocontrol of aflatoxin-producing species.

Mycological and Mycotoxicological Analysis of Maize Imported into Senegal.

Most of the maize used in Senegal comes from abroad. However, no contamination data is available to date for maize imported into Senegal. The objective of this study is to determine the food safety level of maize from France, Argentina and the United States. The analysis of aflatoxins in corn samples is carried out on a High-Performance Liquid Chromatograph. PDA culture medium is used for the isolation, purification and identification of potentially mycotoxinogenic molds contaminating imported corn. The results of the analyzes show the presence of aflatoxins in all the samples. In 35% of the samples, the levels of aflatoxin contamination exceed the standards set by the European regulations in force. They also reveal the presence of mycotoxinogenic molds in this corn. These are two aflatoxin-producing Aspergillus (A. flavus and A parasiticus) and Penicillium sp. As a result, and faced with this threatening situation for public health, Senegal must take a major interest in ensuring that imported products comply with international health standards.

The application of novel rotary plasma jets to inhibit the aflatoxin-producing Aspergillus flavus and the spoilage fungus, Aspergillus niger on peanuts

The major safety risk of peanuts is contamination with aflatoxin. Cold atmospheric plasma (CAP) has been demonstrated to inactivate fungi effectively. In this study, a novel CAP device with a rotary jet system was used to inactivate the existing A. flavus and A. niger on peanuts. The initial inoculation levels were 6.39 and 5.83 log CFU/g of A. flavus and A. niger, respectively. After treatments at 180 W for 7.5 min and 200 W for 5 min, A. flavus was not detected. For A. niger, the treatments at 180 W for 10 min and 200 W for 5 min resulted in undetected population. Observation under scanning electron microscope revealed the fungal spores were evidently damaged. The growth of A. flavus and aflatoxin concentrations were significantly lower (p < 0.05) on the group treated with 200 W for 5 min than other treatment groups stored for 29 d. Oil quality indexes of the CAP-treated peanuts were maintained in the range of excellent grades. This study demonstrated CAP effectively inhibited fungal growth and toxin production without adversely affected oil quality.

Draft Genome Sequence of an Aflatoxin-Producing Aspergillus flavus Strain Isolated from Food.

ABSTRACTAspergillus flavus is the main producer of carcinogenic aflatoxins and thus is one of the most important fungal food contaminants. Here, we report that the genome of A. flavus strain MRI19 was sequenced using MiSeq and PacBio platforms and that a hybrid assembly was generated.

Molecular Detection of Aflatoxin Producing Aspergillus Species Isolates in Some Chicken Meat Cuts In Gharbiya Governorate, Egypt

Contamination with fungi and their toxins is considered one of the most dangerous hidden pollutants that threaten the health of the consumer. The presence of mycotoxins in various foods has been recorded, despite their apparent safety for human consumption. Therefore, the current study was conducted to evaluate the prevalence of Aspergillus species by culture method; and aflatoxin producing genes molecularly in total of 75 random samples of chicken cuts represented by wing, breast and thigh (25 of each) that were collected from various groceries and poultries shops located at Gharbiya governorate, Egypt. Results of culture and isolation techniques revealed detection of Aspergillus sp. in 36, 48 and 44% of the examined wing, breast and thigh samples, respectively. Moreover, microbiological identification of the isolated strains showed presence of A. niger, A. flavus, A. fumigatus, A. terreus and A. parasiticus in 16, 13.3, 10.6, 1.3 and 1.3% of the total population of the examined samples. Molecular detection of some aflatoxin production regulating genes (OmtA, Nor1 and Ver1) in ten Aspergillus sp. isolates revealed their detection in 8/10 (80%), 8/10 (80%) and 7/10 (70%) represented by positive bands at molecular weight of 1024, 400 and 537 bp, respectively. Referring to the recorded results, chicken cuts may possess a great silent hazard to the human-being under improper good manufacturing practices and inadequate hygienic conditions during handling and storage.

Molecular Detection of Aflatoxin Producing Aspergillus species Isolates in some Chicken Meat Cuts in Gharbiya Governorate, Egypt

Contamination with fungi and their toxins is considered one of the most dangerous hidden pollutants that threaten the health of the consumer. The presence of mycotoxins in various foods has been recorded, despite their apparent safety for human consumption. The current study was conducted to evaluate the prevalence of Aspergillus species and aflatoxin producing genes using culture and molecular methods, respectively. A total of 75 samples of chicken cuts, represented by wing, breast, and thigh (25 of each), were randomly collected from various grocery and poultry shops located at Gharbiya governorate, Egypt. Results of culture and isolation techniques revealed the detection of Aspergillus sp. in 36, 48 and 44% of the examined wing, breast and thigh samples, respectively. Moreover, microbiological identification of the isolated strains showed presence of A. niger, A. flavus, A. fumigatus, A. terreus and A. parasiticus in 16, 13.3, 10.6, 1.3 and 1.3% of the total population of the examined samples. Molecular detection of some aflatoxin production regulating genes (OmtA, Nor1 and Ver1) in ten aspergillus sp. isolates revealed their detection in 8/10 (80%), 8/10 (80%) and 7/10 (70%) represented by positive bands at molecular weight of 1024, 400 and 537 bp, respectively. Referring to the recorded results, chicken cuts may possess a great silent hazard to human being under improper good manufacturing practices and inadequate hygienic conditions during handling and storage.

Enzymatic degradation is an effective means to reduce aflatoxin contamination in maize

BackgroundAflatoxins are carcinogenic compounds produced by certain species of Aspergillus fungi. The consumption of crops contaminated with this toxin cause serious detrimental health effects, including death, in both livestock and humans. As a consequence, both the detection and quantification of this toxin in food/feed items is tightly regulated with crops exceeding the allowed limits eliminated from food chains. Globally, this toxin causes massive agricultural and economic losses each year.ResultsIn this paper we investigate the feasibility of using an aflatoxin-degrading enzyme strategy to reduce/eliminate aflatoxin loads in developing maize kernels. We used an endoplasmic reticulum (ER) targeted sub-cellular compartmentalization stabilizing strategy to accumulate an aflatoxin-degrading enzyme isolated from the edible Honey mushroom Armillariella tabescens and expressed it in embryo tissue in developing maize kernels. Three transgenic maize lines that were determined to be expressing the aflatoxin-degrading enzyme both at the RNA and protein level, were challenged with the aflatoxin-producing strain Aspergillus flavus AF13 and shown to accumulate non-detectable levels of aflatoxin at 14-days post-infection and significantly reduced levels of aflatoxin at 30-days post-infection compared to nontransgenic control Aspergillus-challenged samples.ConclusionsThe expression of an aflatoxin-degrading enzyme in developing maize kernels was shown to be an effective means to control aflatoxin in maize in pre-harvest conditions. This aflatoxin-degradation strategy could play a significant role in the enhancement of both US and global food security and sustainability.

Quantification of the Aflatoxin Biocontrol Strain Aspergillus flavus AF36 in Soil and in Nuts and Leaves of Pistachio by Real-Time PCR.

The species Aspergillus flavus and A. parasiticus are commonly found in the soils of nut-growing areas in California. Several isolates can produce aflatoxins that occasionally contaminate nut kernels, conditioning their sale. Strain AF36 of A. flavus, which does not produce aflatoxins, is registered as a biocontrol agent for use in almond, pistachio, and fig crops in California. After application in orchards, AF36 displaces aflatoxin-producing Aspergillus spp. and thus reduces aflatoxin contamination. Vegetative compatibility assays (VCAs) have traditionally been used to track AF36 in soils and crops where it has been applied. However, VCAs are labor intensive and time consuming. Here, we developed a quantitative real-time PCR (qPCR) protocol to quantify proportions of AF36 accurately and efficiently in different substrates. Specific primers to target AF36 and toxigenic strains of A. flavus and A. parasiticus were designed based on the sequence of aflC, a gene essential for aflatoxin biosynthesis. Standard curves were generated to calculate proportions of AF36 based on threshold cycle values. Verification assays using pure DNA and conidial suspension mixtures demonstrated a significant relationship by regression analysis between known and qPCR-measured AF36 proportions in DNA (R2 = 0.974; P < 0.001) and conidia mixtures (R2 = 0.950; P < 0.001). Tests conducted by qPCR in pistachio leaves, nuts, and soil samples demonstrated the usefulness of the qPCR method to precisely quantify proportions of AF36 in diverse substrates, ensuring important time and cost savings. The outputs of this study will serve to design better aflatoxin management strategies for pistachio and other crops.

Effects of temperature and relative humidity on Aflatoxin B1 reduction in corn grains and antagonistic activities against Aflatoxin-producing Aspergillus flavus by a volatile organic compound-producing yeast, Kwoniella heveanensis DMKU-CE82

As shown in our previous study, Kwoniella heveanensis DMKU-CE82, a volatile organic compound (VOC)-producing yeast, demonstrated promising antagonistic activity against aflatoxin-producing strain of Aspergillus flavus. This yeast’s volatile organic compounds (VOCs) could reduce Aflatoxin B1 (AFB1) in corn grains. In the current study, we evaluated the effect of temperatures and relative humidity on AFB1 reduction during grain storage when co-incubated with this VOC-producing yeast. The VOCs produced by K. heveanensis DMKU-CE82 could promote reduction of AFB1 to less than 20 part per billion (ppb) in the fungal contaminated corn grains under most storage conditions at 35 °C. The major VOCs produced by 2-, 4-, and 6-day-old yeast cultures were closely matched to 3-methyl-1-butanol, 2-methyl-1-butanol, hydrazine-1-1-dimethyl, and butanoic acid-3-methyl. In addition, this yeast strain had the ability to produce β-1,3-glucanase, amylase, cellulase, chitinase, siderophores, and biofilms. Scanning electron microscopy also confirmed the antagonistic activity of K. heveanensis DMKU-CE82 as it caused structural damage to conidia and inhibited the development of mycelia and conidiophores in both direct fungal–yeast interaction and the VOC method in corn grains. These results demonstrated that this yeast strain could be a promising biocontrol agent against aflatoxin-producing fungi in agricultural products.

A Comparison of Four Molecular Methods for Detection of Aflatoxin-Producing Aspergillus in Peanut and Dried Shrimp Samples Collected from Local Markets around Pathum Thani Province, Thailand.

Aspergillus flavus is an aflatoxin-producing fungus which is poisonous to humans and animals when consumed. Detecting the fungus can help to prevent this danger. The four molecular methods, namely, conventional isothermal amplification (LAMP), PCR, quantitative LAMP (qLAMP), and qPCR, were compared to determine their efficiency for A. flavus detection. Thirty samples of peanut and dried shrimp were collected from 15 markets around Pathum Thani Province in Thailand. The samples were artificially infected with 108 conidia/ml of A. flavus for 1 hr and enriched for one day to represent real contamination. The results show that the sensitivity detection for A. flavus in PCR, LAMP, qPCR, and qLAMP was 50 ng, 5 ng, 5 pg, and 5 pg, respectively. Aspergillus in 30 peanut and dried shrimp from the market was detected by all four methods. The detection rate was about 20%, 60%, 100%, and 100% with PCR, LAMP, qPCR, and qLAMP, respectively. The molecular detection technique, especially LAMP, qPCR, and qLAMP, can detect this pathogenic fungi very rapidly with high sensitivity and reliability in comparison to conventional PCR.

Using Trichoderma Species in Combination with Cattle Dung as Soil Amendment Improves Yield and Reduces Pre-Harvest Aflatoxin Contamination in Groundnut

Aflatoxin contamination in groundnut constitutes a serious risk to human and animal health. The efficacy of combining five Trichoderma species and cattle dung in the management of aflatoxin-producing Aspergillus flavus under laboratory and field conditions was evaluated. Trichoderma asperellum, T. hamatum, T. viride, T. harzianum and T. pseudokoningii were bioassayed against A. flavus in vitro, while they were applied in combination with cattle dung in the field experiment. A randomized complete block design was used for field treatments with four replications. Trichoderma containing 2.3×108 cfu/gr was applied as seed treatment, while soil application was done using 2.5 kg/ha of sorghum grains as carrier and 5 t/ha cattle dung. Aflatoxin concentration was quantified using high-performance thin-layer chromatography. There was no significant difference among the treatments in the laboratory experiment. However, T. harzianum was the most effective with 72.3% mycelial inhibition of A. flavus. Seed treatment with combination of T. harzianum and cattle dung was most effective in reducing A. flavus soil population to 1.1×103 cfu/gr, while the combination of T. hamatum and cattle dung produced the highest pod yield of 2.7 t/ha, which was significantly higher than carbendazim fungicide. Therefore, integrated approach is recommended in managing aflatoxin contamination in pre-harvest groundnut.

Genetic diversity of aflatoxin-producing Aspergillus flavus isolated from selected groundnut growing agro-ecological zones of Uganda

BackgroundGroundnut pre- and post-harvest contamination is commonly caused by fungi from the Genus Aspergillus. Aspergillus flavus is the most important of these fungi. It belongs to section Flavi; a group consisting of aflatoxigenic (A. flavus, A. parasiticus and A. nomius) and non-aflatoxigenic (A. oryzae, A. sojae and A. tamarii) fungi. Aflatoxins are food-borne toxic secondary metabolites of Aspergillus species associated with severe hepatic carcinoma and children stuntedness. Despite the well-known public health significance of aflatoxicosis, there is a paucity of information about the prevalence, genetic diversity and population structure of A. flavus in different groundnut growing agro-ecological zones of Uganda. This cross-sectional study was therefore conducted to fill this knowledge gap.ResultsThe overall pre- and post-harvest groundnut contamination rates with A. flavus were 30.0 and 39.2% respectively. Pre- and post-harvest groundnut contamination rates with A. flavus across AEZs were; 2.5 and 50.0%; (West Nile), 55.0 and 35.0% (Lake Kyoga Basin) and 32.5 and 32.5% (Lake Victoria Basin) respectively. There was no significant difference (χ2 = 2, p = 0.157) in overall pre- and post-harvest groundnut contamination rates with A. flavus and similarly no significant difference (χ2 = 6, p = 0.199) was observed in the pre- and post-harvest contamination of groundnut with A. flavus across the three AEZs. The LKB had the highest incidence of aflatoxin-producing Aspergillus isolates while WN had no single Aspergillus isolate with aflatoxin-producing potential. Aspergillus isolates from the pre-harvest groundnut samples had insignificantly higher incidence of aflatoxin production (χ2 = 2.667, p = 0.264) than those from the post-harvest groundnut samples. Overall, A. flavus isolates exhibited moderate level (92%, p = 0.02) of genetic diversity across the three AEZs and low level (8%, p = 0.05) of genetic diversity within the individual AEZs. There was a weak positive correlation (r = 0.1241, p = 0.045) between genetic distance and geographic distance among A. flavus populations in the LKB, suggesting that genetic differentiation in the LKB population might be associated to geographic distance. A very weak positive correlation existed between genetic variation and geographic location in the entire study area (r = 0.01, p = 0.471), LVB farming system (r = 0.0141, p = 0.412) and WN farming system (r = 0.02, p = 0.478). Hierarchical clustering using the unweighted pair group method with arithmetic means (UPGMA) revealed two main clusters of genetically similar A. flavus isolates.ConclusionsThese findings provide evidence that genetic differentiation in A. flavus populations is independent of geographic distance. This information can be valuable in the development of a suitable biocontrol management strategy of aflatoxin-producing A. flavus.