Contamination Of Maize Research Articles

Pre-harvest management is a critical practice for minimizing aflatoxin contamination of maize

Maize, the main dietary staple in Kenya, is one of the crops most susceptible to contamination by aflatoxin. To understand sources of aflatoxin contamination for home grown maize, we collected 789 maize samples from smallholder farmers’ fields in Eastern and South Western, two regions in Kenya representing high and low aflatoxin risk areas, respectively, and determined aflatoxin B1 (AFB1) using ELISA with specific polyclonal antibodies. AFB1 was detected in 274 of the 416 samples from Eastern Kenya at levels between 0.01 and 9091.8 μg kg−1 (mean 67.8 μg kg−1). In South Western, AFB1 was detected in 233 of the 373 samples at levels between 0.98 and 722.2 μg kg−1 (mean 22.3 μg kg−1). Of the samples containing AFB1, 153 (55.8%) from Eastern and 102 (43.8%) from South Western exceeded the maximum allowable limit of AFB1 (5 μg kg−1) in maize for human consumption in Kenya. The probable daily intake (PDI) of AFB1 in Eastern Kenya ranged from 0.07 to 60612 ng kg−1 bw day−1 (mean 451.8 ng kg−1 bw day−1), while for South Western, PDI ranged from 6.53 to 4814.7 ng kg−1 bw day−1 (mean 148.4 ng kg−1 bw day−1). The average PDI for both regions exceeded the estimated provisional maximum tolerable daily intake of AFB1, which is a health concern for the population in these regions. These results revealed significant levels of preharvest aflatoxin contamination of maize in both regions. Prevention of preharvest infection of maize by toxigenic A. flavus strains should be a critical focal point to prevent aflatoxin contamination and exposure.

Perennial and seasonal contamination of maize by aflatoxins in eastern Kenya

BackgroundAflatoxin contamination of grain is a major constraint to sustained quality cereal production. The causative fungi, Aspergillus species infect crops in the field and continue to do so post-harvest where they produce toxins in store. The current study aimed at establishing seasonal variation in levels and types of aflatoxins in maize from the Eastern region of Kenya- the hot-spot for aflatoxicosis. Maize kernels were collected from farmers’ households in May and December 2013 -2 months after long rain and short rain season respectively. The total aflatoxins were quantified using Enzyme-Linked Immunosorbent Assay (ELISA), while the toxin composition was determined using Thin-Layer Chromatography (TLC) and confirmed using High-Performance Liquid Chromatography (HPLC).ResultsGenerally, grain harvested after the long rains (May) had significantly (p = 0.019) lower aflatoxin levels and variation (5.68 ± 6.31 ppb, 100% Aflatoxin B1) than that of short rains (10.77 ± 10.14 ppb, 72% AFB1). Additionally, from the long and short rain seasons, the samples exceeding regulatory allowed limit (10 ppb) were 16 and 44% respectively.ConclusionIn Eastern Kenya, consumption of maize harvested in the long rain season presents a recurrent risk of exposure to low levels of AFB1; while consumption of maize harvested after the short rain season presents a risk of seasonal exposure to high levels and mixed type of toxins However, this long term risk of exposure to aflatoxins is poorly documented hence these findings necessitate mitigation measures because AFB1– is a potent class 1 mutagenic toxin likely to cause liver cancer.

Aflatoxins in maize harvested in the Republic of Serbia over the period 2012–2016

ABSTRACTAflatoxins (AFs) are one of the most frequent contaminants in maize. The Republic of Serbia represents a leader in terms of maize production and exports in Europe. In recent years, Serbia faced climate changes. Therefore, the main objective of this study was to examine AF occurrence in 3000 maize samples collected during 2012–2016. In maize samples from 2012, 2013, 2015, and 2016, AFs were detected in 72.3%, 24.7%, 36.7%, and 5.0% of the samples, in concentration ranges of 1.0–111.2, 1.2–65.2, 1.1–76.2, and 1.3–6.9 µg kg−1, respectively. Contrary to this, in maize samples from 2014, no AFs were detected. Analysis of weather conditions indicates that 2012 was characterised by extreme drought conditions, 2013 and 2015 by lack of precipitation and high air temperatures, 2014 as the rainiest year in these years, while 2016 had moderate weather conditions.

Genetic diversity of Aspergillus flavus and occurrence of aflatoxin contamination in stored maize across three agro-ecological zones in Kenya

BackgroundAflatoxin contamination at pre- and post-harvest poses a serious challenge in achieving sustainable development goals on food security and food safety, in particular within the developing world. In Kenya, major outbreaks of aflatoxicoses have been reported and attributed to poor post-harvest storage practices. In this study, we conducted a cross-sectional survey within three Agro-ecological zones in Kenya, to determine occurrence and distribution of total aflatoxin in stored maize and the aflatoxigenicity potential of Aspergillus flavus in stored maize. The counties selected were: Kitui, Nakuru and Trans-Nzoia. Sampling sites were selected based on previous aflatoxicoses outbreaks (Kitui) and major maize production areas (Nakuru and Trans-Nzoia) where little information exists on the occurrence of aflatoxin contamination. One hundred and thirty (130) kernel maize samples were randomly collected. Aspergillus flavus was isolated by direct plating technique. Genetic diversity of the isolates was determined by PCR and single sequence repeats (SSR) microsatellites analysis. Positive strains were induced to produce B1 aflatoxins on yeast extract sucrose agar and quantified using competitive ELISA technique.ResultsTotal aflatoxin contamination of post-harvest stored maize samples between sites was significantly different (p = 0.000, < 0.05), with the highest contamination in Kitale at a mean of (9.68 µg/kg). A. flavus was isolated in 70% (N = 91) of the maize samples collected at post-harvest. A. flavus isolates with the highest aflatoxigenicity potential were from Nakuru County with mean aflatoxin level at 239.7 µg/kg. Genetic distance based on neighbor joining (NJ) clustered the A. flavus isolates into five main clusters including one clade with an admixture. Principal coordinate analysis showed five distinct clusters with both axes explaining 60.17% of the variance.ConclusionThis study showed widespread distribution of aflatoxin contamination and a highly toxigenic A. flavus in stored maize in three major agro-ecological zones in Kenya. These results suggest a potential health risk of aflatoxin outbreaks under favorable conditions within these areas, thus calling for more investigations.

Aflatoxins Contamination in Maize Products from Rural Communities in San Luis Potosi, Mexico.

Background:Aflatoxins are a group of mycotoxins that have been associated with hepatic damage and cancer. Aflatoxins B1 and B2 are secondary metabolites produced by fungi Aspergillus. These toxins can be found in a variety of commodities, especially in maize, and have been studied around the world due to their effects in human health. The Latin American population is especially exposed to aflatoxins given that maize products can be found in traditional diets all over the continent. Interestingly, in Mexico, chronic hepatic diseases and cirrhosis are leading causes of death in adult population.Methods:In order to observe the effect of physical variables like temperature and humidity, this study was conducted collecting samples in four different seasons, in two communities in the State of San Luis Potosi, in Mexico. The content of aflatoxins in tortillas was measured using immunoaffinity columns prior to HPLC-FLD analysis.Findings:Results showed that 18% of samples exceeded the Mexican limits for AFB1; whereas, 26% of the samples exceeded the limits of the European Union for AFB1. The AFB1 was detected in 80% of samples in one site and higher concentrations were found in samples collected during fall and winter seasons.Conclusions:Lack of control in storing practices is the principal cause for the contamination of maize. Considering that maize products are part of the staple diet of Mexican population, our results show that AFB1 detection has to be declared a public health priority. Detection and prevention of aflatoxins through a surveillance program, may avoid chronic health effects.

Pathogenicity and toxigenicity of Fusarium verticillioides isolates collected from maize roots, stems and ears in South Africa

Fusarium verticillioides is most frequently associated with maize in South Africa. It colonises maize roots, stems and ears endophytically and causes diseases such as Fusarium ear rot (FER) and stalk rot. Fusarium verticillioides can produce fumonisins, which are toxic secondary metabolites harmful to humans and animals. It is, however, unknown whether endophytic and pathogenic isolates from distinct maize tissues differ in their ability to cause disease and produce fumonisins. In this study, Fusarium spp. were collected from maize roots, stems and kernels for phylogenetic analysis and the F. verticillioides isolates were subjected to pathogenic and toxigenic comparison. The translation elongation 1-α (TEF1) gene of the isolates was sequenced, and a phylogenetic tree constructed with maximum likelihood (ML) and Bayesian interference (BI) inferred. Fumonisin production of F. verticillioides isolates was determined in vitro and in planta by using high performance liquid chromatography, and virulence of the isolates was determined by silk channel inoculation of maize ears under field conditions. F. verticillioides was the species with the highest number of isolates followed by F. temperatum and then F. subglutinans. Phylogenetic analyses clustered the different Fusarium spp. according to species. Fumonisin production by F. verticillioides isolates varied from 0 to 21.3 mg/kg in vitro, and 0–16.2 mg/kg in planta. All the F. verticillioides isolates produced FER symptoms, including isolates from roots and stems. Fusarium verticillioides isolates in South Africa thus presented a species highly diverse in toxigenicity, but not in virulence. This finding has implications for managing mycotoxins in maize, as visible symptoms might be misleading to the actual toxin level present, for example low level of disease severity might represent high fumonisin levels and vice versa. The high numbers of F. temperatum, also a mycotoxin producer highlights the concern that kernels could be contaminated with more than one mycotoxin. Integrated disease management of not only F. verticillioides but all Fusarium spp. should thus focus strongly on reducing fungal contamination of maize and the detoxification of grain with focus on using regionally adapted maize varieties.

Delaying harvest for naturally drying maize grain increases the risk of kernel rot and fumonisin contamination

Artificial drying, although costly, ensures a safe storage and preserves post-harvest grain quality. Alternatively, a more cost-effective measure is to delay harvest to promote natural drying, but this management may increase the risk of mycotoxigenic ear rot fungi contamination. The objective was to evaluate the effect of increasing maize harvest delay on fungal disease and fumonisin levels. Three maize hybrids (BRS1035, Attack and DKB390 YG) were sown in the field to study the effect of five harvest delays (15, 30, 45, 60 and 75 days) after the optimum date (18% grain moisture). There was a significant trend of increasing the incidence of kernel rot and total fumonisins in the grains when delaying harvest, but fungal incidence and mycotoxin contamination varied with the hybrid. The main fungi detected in the grain samples were Fusarium verticillioides and Stenocarpella maydis. The hybrid DKB390 YG showed significantly lower incidence of F. verticillioides contamination and lower fumonisin accumulation in the grains than the other hybrids. The hybrid Attack was the least susceptible to kernel rot incidence. Our data shows that delaying harvest for minimizing drying costs may increase the risk of mycotoxin contamination in maize in the tropics of Brazil.

Early sowing and harvesting as effective measures to reduce stalk borer injury, Fusarium verticillioides incidence and associated fumonisin production in maize

Maize cultivation in Tanzania is hampered by the presence of maize stalk borer (Busseola fusca) and Fusarium verticillioides, causing ear, kernel and stalk damage. Furthermore, accumulation of fumonisin mycotoxins deteriorates grain quality. Optimized agronomic practices remain the primary line of defense against pests and diseases. Therefore, the aim of this study was to gain insight into the effects of hybrid, sowing and harvest date on injuries due to maize stalk borer, Fusarium verticillioides symptoms and fumonisin contamination in maize grown in Tanzania. The analyses of the data collected during two growing seasons (2013 and 2014) showed early sowing and early harvesting as important measures for minimizing these problems. Although the impact of hybrid was not always significant, the early maturing hybrid STUKA M1 was consistently less susceptible compared to the hybrid STAHA. Correlation analysis revealed that stalk borer injuries, Fusarium symptoms and fumonisin levels were positively associated. The associations between yield and stalk borer injuries, Fusarium symptoms and fumonisin levels were negative, indicating that besides the mycotoxin issues, the insect and fungal pathogen also contribute to yield losses.

Application of Fungicides and Microalgal Phenolic Extracts for the Direct Control of Fumonisin Contamination in Maize.

Fungicides and, for the first time, microalgal phenolic extracts (MPE) from Spirulina sp. and Nannochloropsis sp. were applied on maize culture media under field conditions to evaluate their ability to minimize Fusarium species development and fumonisin production. An in vitro assay against F. verticillioides was carried out using maize grains as the culture medium. An open-field experiment was carried out in Northwest Italy under natural infection conditions. The compared treatments were factorial combinations of two insecticide treatments (an untreated control and pyrethroid, used against European Corn Borer), four antifungal treatments (an untreated control, MPE from Spirulina sp., MPE from Nannochloropsis sp., and a synthetic fungicide), and two timings of the application of the antifungal compounds (at maize flowering and at the milk stage). The MPE compounds were capable of inhibiting fumonisin production in vitro more efficiently than tebuconazole. Insecticide application reduced the infection by Fusarium species and subsequent fumonisin contamination. However, fumonisins in maize fields were not significantly controlled by either fungicide or MPE application.

Dissection of mechanisms of resistance toAspergillus flavus and aflatoxin using tropical maize germplasm

Aspergillus flavus induced ear rots and subsequent contamination of maize (Zea mays L.) by aflatoxin is a serious food safety issue, especially in developing countries where the crop is mostly cultivated by smallholder famers for own consumption and income generation. A better understanding of the mechanisms of resistance could help breeders to develop resistant maize varieties. In this study, a set of six tropical maize inbred lines previously identified as resistant or susceptible under natural field conditions were evaluated for response toA. flavus colonisation and aflatoxin contamination. Fungal biomass was significantly higher (P&lt;0.05) in susceptible than resistant maize inbred lines, and this was highly correlated (P=0.001) to aflatoxin levels. Maize inbred lines MRI, MR2 and MR3 had low fungal biomass and low aflatoxin levels, suggesting that resistance in these lines was mediated through restricted fungal colonisation and establishment. Among the three putatively resistant inbred lines mentioned above, MR2 had a relatively high colonisation compared to the other two lines, revealing thatA. flavus could establish and colonise kernels that were injured during inoculation, but did not contain high levels of aflatoxin. This could signify the presence of host genes that interfere with the aflatoxin biosynthetic pathway.

Rice Phyllosphere Bacillus Species and Their Secreted Metabolites Suppress Aspergillus flavus Growth and Aflatoxin Production In Vitro and In Maize Seeds.

The emergence of super-toxigenic strains by recombination is a risk from an intensive use of intraspecific aflatoxin (AF) biocontrol agents (BCAs). Periodical alternation with interspecific-BCAs will be safer since they preclude recombination. We are developing an AF-biocontrol system using rice-associated Bacilli reported previously (RABs). More than 50% of RABs inhibited the growth of multiple A. flavus strains, with RAB4R being the most inhibitory and RAB1 among the least. The fungistatic activity of RAB4R is associated with the lysis of A. flavus hyphal tips. In field trails with the top five fungistatic RABs, RAB4R consistently inhibited AF contamination of maize by Tox4, a highly toxigenic A. flavus strain from Louisiana corn fields. RAB1 did not suppress A. flavus growth, but strongly inhibited AF production. Total and HPLC-fractionated lipopeptides (LPs) isolated from culture filtrates of RAB1 and RAB4R also inhibited AF accumulation. LPs were stable in vitro with little loss of activity even after autoclaving, indicating their potential field efficacy as a tank-mix application. A. flavus colonization and AF were suppressed in RAB1- or RAB4R-coated maize seeds. Since RAB4R provided both fungistatic and strong anti-mycotoxigenic activities in the laboratory and field, it can be a potent alternative to atoxigenic A. flavus strains. On the other hand, RAB1 may serve as an environmentally safe helper BCA with atoxigenic A. flavus strains, due its lack of strong fungistatic and hemolytic activities.

Gene expression analysis to predict aflatoxins B1 and G1 contamination in some plant origin foods

Maize, peanuts and wheat are exposed to colonisation by Aspergillus flavus and Aspergillus parasiticus, which are mould species able to produce aflatoxins B1 (AFB1) and G1 (AFG1). New tools based on molecular data can be used to obtain critical information to prevent AFs accumulation in these crops. The objective of this study was to analyse the time course of the relative expression of the aflR, aflS and aflP genes by reverse transcription real-time PCR (RT-qPCR) in relation to AFs production by A. flavus and A. parasiticus on maize, peanuts and wheat under controlled conditions during nine days of incubation. Different gene expression profiles for the three target genes were observed in maize, peanut and wheat. In general, AFB1 amounts produced by both species were increased over incubation time, although A. parasiticus produced higher AFB1 quantities than A. flavus in peanuts and wheat. Regarding AFG1 production, quantities were higher at the end of the incubation time but lower than AFB1 amounts. High relationships were found between gene expression by day 4 and AFs production by days 7 and 9. Thus, gene expression data allow predicting early AFs contamination of maize and wheat. In the case of peanuts further studies are needed.

Occurrence of filamentous fungi in maize destined for human consumption in South Africa.

One‐hundred maize samples were analyzed for fungal contamination using conventional and molecular methods. The percentage incidence of different genera isolated revealed the predominance of Fusarium (82%), Penicillium (63%), and Aspergillus species (33%) compared to other genera. Fusarium occurred in 90% and 74% of small scale and commercial samples, respectively, while Penicillium occurred in small scale and commercial samples at an incidence rate of 64% and 62%, respectively. However, among the species, Fusarium verticilloides have the highest incidence of 70% and 76% in commercial and small‐scale maize, respectively, while Penicillium digitatum has 56% total incidence. Aspergillus fumigatus (27%) were also the most dominant of these genera. Fungal genera isolated included Alternaria and Cladosporium although occurring at a lower incidence level of 30%, 32% and 16%, 20%, respectively, in small‐scale and commercial samples. The results emphasize that farmers and consumers should be alerted to the danger of fungal contamination in maize.

The Aspergillus flavus Spermidine Synthase (spds) Gene, Is Required for Normal Development, Aflatoxin Production, and Pathogenesis During Infection of Maize Kernels.

Aspergillus flavus is a soil-borne saprophyte and an opportunistic pathogen of both humans and plants. This fungus not only causes disease in important food and feed crops such as maize, peanut, cottonseed, and tree nuts but also produces the toxic and carcinogenic secondary metabolites (SMs) known as aflatoxins. Polyamines (PAs) are ubiquitous polycations that influence normal growth, development, and stress responses in living organisms and have been shown to play a significant role in fungal pathogenesis. Biosynthesis of spermidine (Spd) is critical for cell growth as it is required for hypusination-mediated activation of eukaryotic translation initiation factor 5A (eIF5A), and other biochemical functions. The tri-amine Spd is synthesized from the diamine putrescine (Put) by the enzyme spermidine synthase (Spds). Inactivation of spds resulted in a total loss of growth and sporulation in vitro which could be partially restored by addition of exogenous Spd. Complementation of the Δspds mutant with a wild type (WT) A. flavus spds gene restored the WT phenotype. In WT A. flavus, exogenous supply of Spd (in vitro) significantly increased the production of sclerotia and SMs. Infection of maize kernels with the Δspds mutant resulted in a significant reduction in fungal growth, sporulation, and aflatoxin production compared to controls. Quantitative PCR of Δspds mutant infected seeds showed down-regulation of aflatoxin biosynthetic genes in the mutant compared to WT A. flavus infected seeds. Expression analyses of PA metabolism/transport genes during A. flavus-maize interaction showed significant increase in the expression of arginine decarboxylase (Adc) and S-adenosylmethionine decarboxylase (Samdc) genes in the maize host and PA uptake transporters in the fungus. The results presented here demonstrate that Spd biosynthesis is critical for normal development and pathogenesis of A. flavus and pre-treatment of a Δspds mutant with Spd or Spd uptake from the host plant, are insufficient to restore WT levels of pathogenesis and aflatoxin production during seed infection. The data presented here suggest that future studies targeting spermidine biosynthesis in A. flavus, using RNA interference-based host-induced gene silencing approaches, may be an effective strategy to reduce aflatoxin contamination in maize and possibly in other susceptible crops.

Control of Aspergillus flavus growth and aflatoxin production in transgenic maize kernels expressing a tachyplesin-derived synthetic peptide, AGM182

Aspergillus flavus is an opportunistic, saprophytic fungus that infects maize and other fatty acid-rich food and feed crops and produces toxic and carcinogenic secondary metabolites known as aflatoxins. Contamination of maize with aflatoxin poses a serious threat to human health in addition to reducing the crop value leading to a substantial economic loss. Here we report designing a tachyplesin1-derived synthetic peptide AGM182 and testing its antifungal activity both in vitro and in planta. In vitro studies showed a five-fold increase in antifungal activity of AGM182 (vs. tachyplesin1) against A. flavus. Transgenic maize plants expressing AGM182 under maize Ubiquitin-1 promoter were produced through Agrobacterium-mediated transformation. PCR products confirmed integration of the AGM182 gene, while RT-PCR of maize RNA confirmed the presence of AGM182 transcripts. Maize kernel screening assay using a highly aflatoxigenic A. flavus strain (AF70) showed up to 72% reduction in fungal growth in the transgenic AGM182 seeds compared to isogenic negative control seeds. Reduced fungal growth in the AGM182 transgenic seeds resulted in a significant reduction in aflatoxin levels (76–98%). The results presented here show the power of computational and synthetic biology to rationally design and synthesize an antimicrobial peptide against A. flavus that is effective in reducing fungal growth and aflatoxin contamination in an economically important food and feed crop such as maize.

Prevalence of Aflatoxin Contamination in Maize and Groundnut in Ghana: Population Structure, Distribution, and Toxigenicity of the Causal Agents.

Aflatoxin contamination in maize and groundnut is perennial in Ghana with substantial health and economic burden on the population. The present study examined for the first time the prevalence of aflatoxin contamination in maize and groundnut in major producing regions across three agroecological zones (AEZs) in Ghana. Furthermore, the distribution and aflatoxin-producing potential of Aspergillus species associated with both crops were studied. Out of 509 samples (326 of maize and 183 of groundnut), 35% had detectable levels of aflatoxins. Over 15% of maize and 11% of groundnut samples exceeded the aflatoxin threshold limits set by the Ghana Standards Authority of 15 and 20 ppb, respectively. Mycoflora analyses revealed various species and morphotypes within the Aspergillus section Flavi. A total of 5,083 isolates were recovered from both crops. The L morphotype of Aspergillus flavus dominated communities with 93.3% of the population, followed by Aspergillus spp. with S morphotype (6%), A. tamarii (0.4%), and A. parasiticus (0.3%). Within the L morphotype, the proportion of toxigenic members was significantly (P < 0.05) higher than that of atoxigenic members across AEZs. Observed and potential aflatoxin concentrations indicate that on-field aflatoxin management strategies need to be implemented throughout Ghana. The recovered atoxigenic L morphotype fungi are genetic resources that can be employed as biocontrol agents to limit aflatoxin contamination of maize and groundnut in Ghana.

Biological Control Products for Aflatoxin Prevention in Italy: Commercial Field Evaluation of Atoxigenic Aspergillus flavus Active Ingredients.

Since 2003, non-compliant aflatoxin concentrations have been detected in maize produced in Italy. The most successful worldwide experiments in aflatoxin prevention resulted from distribution of atoxigenic strains of Aspergillus flavus to displace aflatoxin-producers during crop development. The displacement results in lower aflatoxin concentrations in harvested grain. The current study evaluated in field performances of two atoxigenic strains of A. flavus endemic to Italy in artificially inoculated maize ears and in naturally contaminated maize. Co-inoculation of atoxigenic strains with aflatoxin producers resulted in highly significant reductions in aflatoxin concentrations (>90%) in both years only with atoxigenic strain A2085. The average percent reduction in aflatoxin B1 concentration in naturally contaminated maize fields was 92.3%, without significant differences in fumonisins between treated and control maize. The vegetative compatibility group of A2085 was the most frequently recovered A. flavus in both treated and control plots (average 61.9% and 53.5% of the A. flavus, respectively). A2085 was therefore selected as an active ingredient for biocontrol products and deposited under provisions of the Budapest Treaty in the Belgian Co-Ordinated Collections of Micro-Organisms (BCCM/MUCL) collection (accession MUCL54911). Further work on development of A2085 as a tool for preventing aflatoxin contamination in maize produced in Italy is ongoing with the commercial product named AF-X1™.

Field Assessment of Agronomic Performance, Resistance to Aflatoxin, and Fumonisin Accumulation in Selected Maize Inbred Lines in Kenya

<i>Aspergillus flavus</i> and <i>Fusarium verticilloides</i> cause contamination of maize (<i>Zea mays</i>) and concern to maize farmers because they reduce maize quantity and quality. These fungi produce mycotoxins, some of which are poisonous to both humans and animals. Over 300 mycotoxins are known but in this study aflatoxins and fumonisins produced by <i>A. flavus</i> and <i>F. verticilloides</i>, respectively, are reported due to their health concerns in Africa. Contamination of maize grain by these fungi occurs before harvest and selection of maize parental lines resistant to accumulation of aflatoxin, and fumonisin for breeding purposes is the easiest strategy to reduce consumption of maize grains contaminated by these toxins. In addition to selecting for resistant lines, breeders would prefer inbred lines with top performing agronomic traits. This study aimed at identifying possible source of resistance together with good agronomic traits among 23 maize inbred lines (13 sourced from the MAIZE Competitive Grants Initiative, International Maize and Wheat Improvement Centre and 10 from Agricultural Research Council, South Africa). The lines were planted in two blocks; <i>Aspergillus</i>, and <i>Fusarium</i>, in a randomized complete-block design for two seasons in one location in Kenya. Germination rate, days to silking, and days to anthesis were determined in each line. Inoculation of the maize ears was done at silking with three toxigenic strains of <i>A. flavus</i> for <i>Aspergillus</i> block, and <i>F. verticilloides</i> for <i>Fusarium</i> block. Aflatoxins and fumonisins concentration in the kernels was determined using Enzyme-linked immunosorbent assay (ELISA). A positive significant correlation (r = 0.9458846, P = < 9.845e-12) occurred between days to anthesis and days to silking, aflatoxins and fumonisins (r = 0.43149988, P ≤ 0.05) accumulated in the inbred lines. A negative correlation between germination and accumulated fumonisin levels (r = -0.5156961, P = 0.01178), days to pollen shed and aflatoxin (r = -0.4617732, P = 0.02654) was revealed. Apart from being good germinating lines and drought tolerant, CML 390 and CML 247 accumulated least fumonisin, and aflatoxin levels compared to the other germplasms. These two lines with consistent low aflatoxin, and fumonisin levels may, therefore be useful sources of resistance for maize breeding programs to reduce both aflatoxin and fumonisn contamination in maize. Four aflatoxin resistant lines (CB 222, CML 495 and CML 444) and one (CKL05003) fumonisin resistant line showed good agronomic traits. The lines may be suitable for breeding for resistance to aflatoxins, and fumonisins respectively in maize.

Assessment of aflatoxin B1 in maize and awareness of aflatoxins in Son La, Vietnam

ABSTRACTAflatoxin B1 (AFB1) is a fungal by-product which causes acute and chronic toxicity in humans and many other animals. This research was conducted to evaluate the prevalence of AFB1 contamination in maize and residents’ awareness of aflatoxins in Son La province, Vietnam. Maize samples were randomly collected from Son La province using multi-stage sampling. We used cut-off levels of 5 and 20 μg/kg and calculated the mean, median and range for each district. In addition, a questionnaire collected information from households about their knowledge, attitude and practice related to moldy maize. Out of 378 maize samples from Son La, 204 (54.0%) and 141 (37.3%) were contaminated with AFB1 at more than 5 µg/kg and 20 µg/kg, respectively. Mai Son district had the highest proportion of samples (54.0%) using a cut-off level > 20 µg/kg, and Yen Chau district the lowest (4%). People from the Thai ethnic group were 30.9 times more likely to consume meat from animals fed moldy maize than people from the Kinh ethnic group (p = 0.003). Maize in Son La is contaminated with AFB1 at levels which imply better control of aflatoxins in maize for human consumptions and animal feed is needed.

Fumonisin B1 induces oxidative stress in oesophageal (SNO) cancer cells

Fumonisin B1 (FB1) is a ubiquitous contaminant of maize that is epidemiologically linked to oesophageal cancer (OC) in South Africa. FB1-induced oxidative stress mediates toxicity in animals and human cell lines, but the effects relating to OC are limited. Given the species-specific effects of FB1, this study investigated FB1-mediated toxicity and oxidative stress in spindle-shaped N-cadherin (+) CD45 (−) osteoblastic (SNO) cells. Following exposure to FB1 (0–20 μM) for 48 h, mitochondrial membrane potential and intracellular reactive oxygen species (iROS) were measured (flow cytometry). Malondialdehyde concentration (lipid peroxidation) was determined spectrophotometrically. ATP and reduced glutathione (GSH) concentrations were quantified using luminometry, gene expression of SOD2 by qPCR and protein expression of SOD2, GPx1, Nrf2 and HSP70 by western blotting. Mitochondrial depolarization increased at 10 μM and 20 μM FB1, with a concomitant reduction in ATP, iROS and GSH at both concentrations. Lipid peroxidation increased at 10 μM FB1 exposure. While transcript levels of SOD2 were significantly increased, protein levels decreased. Protein expression of GPx1, Nrf2 and HSP70 increased. In contrast to the 10 μM and 20 μM FB1 treatment, mitochondrial depolarization decreased at 1.25 μM FB1. Intracellular ROS and ATP were decreased and lipid peroxidation increased. Decreased GSH was accompanied by a decrease in GPx1 protein levels, and increased HSP70 and Nrf2. SOD2 expression and protein levels were significantly increased. Overall these results indicate that FB1 caused increased ROS that were counteracted by engaging the antioxidant defense. Furthermore, the peculiar response at 1.25 μM FB1 is noteworthy, as compared to the other two concentrations tested.