Local post-harvest practices associated with aflatoxin and fumonisin contamination of maize in three agro ecological zones of Tanzania

A survey was undertaken of a total of 120 farmers, 40 from each of the three studied agro-ecological zones of Tanzania, to determine local post-harvest management practices associated with aflatoxin (AF) and fumonisin (FB) contamination of maize. Data on practices (collected using a structured questionnaire) and maize samples were obtained from each of the 120 farmers. FB and AF contamination in the samples were analysed by HPLC. A total of 45% and 85% of maize samples were positive for AF and FB respectively, with levels ranging from 0.1 to 269 μg kg^?1 for AF and from 49 to 18 273 μg kg^?1 for FBs. Significant differences in contamination level were observed among the three agro-ecological zones. Farmers in the three agro-ecological zones practised similar practices in varying degrees. Drying, sorting and protecting maize against insect infestation are practices that showed significant association with AF or FB contamination of maize. Drying maize on mat/raised platform, sorting (damaged, discoloured and moulded grains) and application of synthetic insecticides during storage are practices that were associated with less contamination of maize with AF and FB. The results can be used to advise on effective post-harvest strategies for prevention of AF and FB contamination of maize in rural Tanzania.     

Kinetics of fumonisin B1 formation in maize ears inoculated with Fusarium verticillioides

The kinetics of fumonisin B₁ (FB₁) biosynthesis have been examined in ears of four botanical varieties Zea mays var. indentata, Zea mays var. indurata, Zea mays var. saccharata and Zea mays var. everta inoculated with F. verticillioides isolates at silking stage. The level of mycotoxin accumulated in kernels was correlated with sample harvest time (r?=?0.73) and ergosterol content (r?=?0.70). FB₁ biosynthesis was influenced by amylose, starch and moisture contents, which undergo dynamic changes during grain formation. A comparative analysis of ear infection rates and efficiency of FB₁ biosynthesis showed that these are separate characters and their expression could be independent.     

Timing clorpirifos + cypermethrin and indoxacarb applications to control European corn borer damage and fumonisin contamination in maize kernels

BACKGROUND: European corn borer (ECB) is the main maize pest in central and southern Europe and it promotes the infection of maize with Fusarium verticillioides, which is able to produce fumonisins. Field experiments were performed from 2006 to 2007 in northwestern Italy to determine the effects of the timing of insecticide applications on maize fungal ear rot and fumonisin contamination in natural infection conditions. Four application timings and two insecticides (clorpirifos + cypermethrin and indoxacarb) were compared each year. RESULTS: In both years, the treatments applied at the beginning of a consistent ECB flight activity and at the flight peak showed the best efficacy to control the insect damage on ears. Fungal ear rot and fumonisin contamination were clearly affected by ECB control. The efficacy of the best application timing to control fumonisin occurrence was 73% in 2006 and 84% in 2007. Earlier insecticide applications showed lower fumonisin contamination than treatments applied after the adult flight peak. CONCLUSION: The production of maize and maize‐based foods with a low fumonisin content may be enhanced through correct insecticide application against the second ECB generation. The optimum timing of insecticides is between the beginning of a consistent adult flight activity and the flight peak. Copyright © 2009 Society of Chemical Industry     

Relative severity of fumonisin contamination of cereal crops in West Africa

Traditional and improved varieties of maize, pearl millet and sorghum were planted by small-scale farmers under the direction of the International Institute for Tropical Agriculture in two Nigerian agro-ecological zones: the Sudan Savanna and the Northern Guinea Savanna. Samples were collected for the determination of Fusarium infection and fumonisin (B₁, B₂ and B₃) contamination. A previous paper reported Aspergillus infection and aflatoxin contamination of these samples. Fusarium infection levels, measured by per cent kernels infected, were modest with mean levels for the above cereals of 16% ± 11% (SD), 12% ± 7% and 13% ± 16%, respectively. However, the Fusarium species recovered from maize were predominantly the fumonisin producers F. verticillioides and F. proliferatum, together making an infection rate of 15% ± 10%, whereas these species were present to a limited extent only in the other two cereals, 1% ± 1% for pearl millet and 2% ± 6% for sorghum. Fumonisin contamination was variable but reflected the diversity of Fusarium producers in these three cereals. Mean levels were 228 ± 579 µg kg^–1 (range < 5–2860 µg kg^–1) for maize, 18 ± 7 µg kg^–1 (range = 6–29 µg kg^–1) for pearl millet and 131 ± 270 µg kg^–1 (range < 5–1340 µg kg^–1) for sorghum. Together with previous results on aflatoxin, this study confirmed the co-occurrence of aflatoxins and fumonisins in maize as well as in the traditional African cereals, millet and sorghum (89% co-occurrence across all three cereals). The low fumonisin levels may be ascribed to the use of good agricultural practices. Of the Fusarium species present, those in maize consisted mainly of fumonisin producers, the opposite of what was observed in pearl millet and sorghum. It is concluded that replacement of maize by pearl millet and sorghum could improve food safety with regards to aflatoxin B and fumonisin B exposure.     

Fumonisin contamination of maize hybrids visibly damaged by Sesamia

Sesamia nonagrioides Lefebvre (Lepidoptera: Noctuidae) is the main insect pest of maize cultivated in Mediterranean areas, causing an increase in broken plants, a reduction in yield and a decline in grain quality. An investigation of Sesamia attacks and fumonisin accumulation on 25 maize hybrids sown as a second crop after wheat has been performed under field conditions in Central Italy in 2000. The hybrids tested in this study showed different degrees of insect damage, ranging from 12 to 57% of damaged ears per hybrid. Over 50% of the tested hybrids showed strong insect damage, with more than 30% of harvested ears visibly damaged by Sesamia. Fungal contamination by Fusarium verticillioides and F proliferatum, two well‐known producers of fumonisins, was detected in both symptomless and insect‐damaged samples. Fumonisin analysis of healthy‐looking and insect‐damaged ear samples of each hybrid showed 100% incidence of positive samples, with fumonisin contents ranging from 0.01 to 20 mg kg^?1 for healthy‐looking ears and from 27 ± 32 to 287 ± 221 mg kg^?1 for insect‐damaged ears. Extremely high levels of fumonisins were found in ear samples visibly damaged by Sesamia, with individual values of up to 694 mg kg^?1 and average values exceeding 100 mg kg^?1 in more than 50% of the hybrids. A good correlation (r = 0.749) was found between fumonisin contamination and the degree of insect damage by Sesamia of the tested hybrids, calculated on the basis of percentage of ears visibly damaged by insects and with more than 5% kernel loss. This finding leads to the conclusion that insect damage by Sesamia on maize could be used as an early indicator of fumonisin contamination. © 2002 Society of Chemical Industry     

The influence of local factors on the prediction of fumonisin contamination in maize

BACKGROUND: Contamination by mycotoxins is a major concern to the maize industry in north‐east Italy where maize grain is often spoiled by Fusarium spp. In this work, fumonisins, deoxynivalenol and zearalenone were determined and an artificial neural network (ANN) model suitable for predicting mycotoxin contamination of maize at harvest time was developed. RESULTS: The occurrence of deoxynivalenol and zearalenone was very limited, while fumonisins concentration ranged from 163 and to 3663 µg kg^?1 in 2007, and from 333 to 11473 µg kg^?1 in 2008. Statistical data analysis of factors affecting fumonisins concentration revealed that irrigation, chemical treatment against the European corn borer and harvest date significantly affected the level of contamination (P < 0.05), although the relevance of the factors was different in 2007 and 2008. The neural network approach showed a significant correlation between ascertained values and predictions based on agronomic data. CONCLUSION: This is the first time that an artificial neural network has been used to predict fumonisin accumulation in maize: the prediction has been shown to have the potential for the development of a new approach for the rapid cataloging of grain lots. Copyright © 2012 Society of Chemical Industry     

Impact of mechanical shelling and dehulling on Fusarium infection and fumonisin contamination in maize

Mechanical shelling and dehulling methods were tested to evaluate their impact on Fusarium infection and fumonisin contamination in maize. All shelling methods which were tested were found to damage the grains. The IITA® sheller caused the highest level (up to 3.5%) of damage. Fusarium populations were higher on damaged grains, the highest being recorded from grains damaged by the IITA® sheller (2533.3 cfu g^-1). Fumonisin levels were higher in damaged grains, the highest being in maize shelled with the IITA® sheller (2.2 mg kg^-1). Fumonisin levels were positively and significantly correlated with the percentage of damage caused by the shelling methods, and with the number of Fusarium colonies in maize. Mechanical dehulling methods significantly reduced fumonisin levels in maize, resulting in a mean reduction of 62% for Mini-PRL, 65% for Engelberg, and 57% for the attrition disc mill. It is important for farmers to choose appropriate shelling methods to reduce mycotoxin contamination. Dehulling should be widely promoted for the reduction of mycotoxins in maize.     

Mycotoxin contamination of maize hybrids after infection with Fusarium proliferatum

The ear rot severity of nine maize hybrids and the accumulation of fumonisin B₁(FB₁), fumonisin B₂(FB₂), beauvericin (BEA) and fusaproliferin (FP) after artificial inoculation in the field with a toxigenic strain of Fusarium proliferatum have been investigated. Different degrees of ear rot were observed in different hybrids. Inoculated ears contained 11–38% of Fusarium-damaged kernels (FDK). Mycotoxin analyses showed a pronounced contamination of FDK with concentrations ranging from 116 to 343 mg kg⁻¹ for FB₁, from 8 to 29 mg kg⁻¹ for FB₂, from 1 to 14 mg kg⁻¹ for BEA and from 2 to 10 mg kg⁻¹ for FP. Lower levels of contamination were found in healthy-looking kernels (up to 26, 2, 0.2 and 0.3 mg kg⁻¹ for FB₁, FB₂, BEA and FP respectively). A good correlation was observed between mycotoxin contamination and the Fusarium ear rot index, calculated on the basis of average ear infection with a scale ranging from 0 to 500 to represent healthy cobs and totally rotted cobs respectively. © 1999 Society of Chemical Industry     

Impact of environment and interactions of Fusarium verticillioides and Fusarium proliferatum with Aspergillus parasiticus on fumonisin B1 and aflatoxins on maize grain

Fusarium verticillioides and F proliferatum isolates were inoculated in mixed cultures with Aspergillus parasiticus on irradiated maize grain at two different inoculum concentrations (2 × 10⁵ and 2 × 10² conidia g^?1 dry maize). The treatments were 0.93–0.98 water activity (a_w) and 15 and 25 °C for 28 days. A complex relationship was found between a_w, temperature, inoculum concentration and the interactions which took place between fumonisin and aflatoxin producers. In general, A parasiticus reduced F verticillioides and F proliferatum populations (by 6–36%) but did not affect fumonisin B₁ production by these species. In contrast, while the Fusarium species were not able to decrease A parasiticus populations, they significantly reduced aflatoxin B₁ accumulation (by 30–93%). © 2001 Society of Chemical Industry     

Determination of the mycotoxin fumonisin B1 in maize by reversed-phase thin-layer chromatography: a collaborative study

A simple and cost-effective method using thin-layer chromatography for the determination of the mycotoxin fumonisin B₁ in maize is described. The analytical method consisted of the extraction of ground maize by shaking with methanol/water (75:25) for 60 min and clean-up of the resultant extract by means of strong anion exchange solid-phase extraction. The purified residue, formed by evaporation of the elution solvent, was reacted with fluorescamine and the fumonisin B₁-derivative was separated by reversed-phase thin-layer chromatography using a developing solution of methanol/aqueous 4% potassium chloride (70:30). The derivatized FB₁ was readily visualized as a greenish-yellow spot under long wavelength ultraviolet light and quantified by visual comparison with a set of similarly derivatized standards in the range 20-300 ng FB₁ spotted on plate. Based on visual comparison, levels down to 0.5 mg kg^-1 were successfully estimated. The method was collaboratively studied in 14 laboratories using four duplicate maize meal samples (including a blank) and a spiked sample for determination of recovery. No significant difference was observed between mean FB₁ levels by high-performance liquid chromatography or thin-layer chromatography. Based on within-laboratory relative standard deviations of 27.1-41.7% and between-laboratory relative standard deviations of 35.0-63.3%, the method can be considered semiquantitative. The mean recovery achieved by participants at a spiking level of 2.00 mg kg^-1 was 74.5%.     

Associations of planting date,drought stress,and insects with Fusarium ear rot and fumonisin B1 contamination in California maize

Fusarium ear rot, caused by Fusarium verticillioides, is one of the most common diseases of maize, causing yield and quality reductions and contamination of grain by fumonisins and other mycotoxins. Drought stress and various insects have been implicated as factors affecting disease severity. Field studies were conducted to evaluate the interactions and relative influences of drought stress, insect infestation, and planting date upon Fusarium ear rot severity and fumonisin B₁ contamination. Three hybrids varying in partial resistance to Fusarium ear rot were sown on three planting dates and subjected to four irrigation regimes to induce differing levels of drought stress. A foliar-spray insecticide treatment was imposed to induce differing levels of insect injury. Populations of thrips (Frankliniella spp.), damage by corn earworm (Helicoverpa zeae), Fusarium ear rot symptoms, and fumonisin B₁ levels were assessed. There were significant effects of hybrid, planting date, insecticide treatment, and drought stress on Fusarium ear rot symptoms and fumonisin B₁ contamination, and these factors also had significant interacting effects. The most influential factors were hybrid and insecticide treatment, but their effects were influenced by planting date and drought stress. The more resistant hybrids and the insecticide-treated plots consistently had lower Fusarium ear rot severity and fumonisin B₁ contamination. Later planting dates typically had higher thrips populations, more Fusarium ear rot, and higher levels of fumonisin B₁. Insect activity was significantly correlated with disease severity and fumonisin contamination, and the correlations were strongest for thrips. The results of this study confirm the influence of thrips on Fusarium ear rot severity in California, USA, and also establish a strong association between thrips and fumonisin B₁ levels.     

Fumonisin B1, fumonisin B2, zearalenone and ochratoxin A contamination of maize in Croatia

Mycotoxins are products of moulds that frequently contaminate maize. In this study the presence of mycotoxins fumonisin B₁ (FB₁), fumonisin B₂ (FB₂), zearalenone (ZEA) and ochratoxin A (OTA) was determined in 49 maize grain samples collected in autumn 2002. The most frequent finding was that of FB₁(100%), followed by ZEA (84%) and OTA (39%), while FB₂ was found only in three samples. The co-occurrence of two and three mycotoxins was found in 55 and 37% of samples, respectively. The concentrations (mean ± SD) of FB₁, ZEA and OTA in positive samples were 459.8 ± 310.7, 3.84 ± 6.68 and 1.47 ± 0.38 µg kg^-1, respectively, and the concentrations of FB₂ in three positive samples were 68.4, 109.2 and 3084.0 µg kg^-1. Although such low concentrations of mycotoxins are not a significant source of exposure in countries with a European diet, a few samples with extreme values indicate that thorough control is needed.     

Air analysis in the assessment of fumonisin contamination risk in maize

BACKGROUND: In maize‐growing areas where fumonisin contamination is endemic, there is an urgent need for novel methods to assess the quality of grain lots before their delivery to common drying and storage collection centres. Aerobiological samples of fungal spores released during harvest were analysed to establish a relationship between fumonisin contamination and the abundance of pathogen propagules collected in the combine harvester using a cyclone and membrane filters. Filter‐captured propagules were analysed by direct plating, immunoenzymatic assay of specific Fusarium extracellular polysaccharides and real time polymerase chain reaction of the extracted DNA using fum1, a gene involved in the biosynthesis of fumonisin, as a target. RESULTS: The results showed that time of harvest and environmental conditions strongly influenced the efficiency and performance of the collection system. The data obtained were informative in comparing individual samples collected under similar conditions. The immunoenzymatic assay provided the most reliable data, which improved the ability of a neural network to predict the fumonisin content of lots, when added to agronomic, environmental and phytosanitary data. CONCLUSION: This is the first attempt to evaluate the Fusarium propagules dispersed during harvesting as a predictive means to assess maize quality. A method based on cyclone/filter capture and immunological detection has been shown to be feasible and to have the potential for the development of a continuous monitoring system, but the prediction capabilities in the present implementation were limited. Copyright © 2010 Society of Chemical Industry     

Wheat kernel black point and fumonisin contamination by Fusarium proliferatum

Fusarium proliferatum is a major cause of maize ear rot and fumonisin contamination and also can cause wheat kernel black point disease. The primary objective of this study was to determine whether nine F. proliferatum strains from wheat from Nepal can cause black point and fumonisin contamination in wheat kernels. For comparison, the study included three Fusarium strains from US maize. In test 1, all the strains but one produced significant symptoms of kernel black point; two strains decreased kernel yield; and four strains contaminated kernels with fumonisins B₁, B₂ and B₃ as determined by liquid chromatography-mass spectroscopy. Strain Ggm202 from Nepal, which produced the highest levels of fumonisins (mean = 49 µg g^-1) on five wheat cultivars in test 1, was confirmed to produce fumonisins (mean = 38 µg g^-1) on two cultivars in test 2. The data indicate a potential for fumonisin contamination of wheat infected with F. proliferatum.     

Electronic nose predicts high and low fumonisin contamination in maize cultures

The ability of an electronic nose, based on a 6 metal oxide semiconductor chemical sensors array, to diagnose fungal contamination, to detect high fumonisin content and to predict fumonisin concentration was evaluated in vitro. Maize cultures were inoculated with Fusarium verticillioides, F. proliferatum, F. oxysporum, F. semitectum, F. solani and F. subglutinans. Sterilised maize cultures were used as reference. Fungal colonies and fumonisin content of the maize samples were used as covariates for statistical analyses and for electronic nose training. Univariate and multivariate exploratory data analysis showed that the electronic nose discriminated the inoculated maize culture samples according to their fumonisin content. Partial Least Square was also implemented to build a multivariate regression model based on EN signals for quantitative fumonisin prediction. The EN could correctly recognize high and low fumonisin content of maize cultures and provide a fair quantitative estimation. The validity of EN technology to perform a rapid screening of maize cultures in order to identify levels of fumonisin contamination below the acceptability threshold was established.     

Effect of essential oils of cinnamon,clove, lemon grass,oregano and palmarosa on growth of and fumonisin B1 production by Fusarium verticillioides in maize

The ability of cinnamon, clove, lemon grass, oregano and palmarosa essential oils to prevent growth of and fumonisin B₁ (FB₁) production by Fusarium verticillioides at different water activity (0.95 and 0.995 a_w) and temperature (20 and 30 °C) levels in irradiated maize grain was evaluated. All the essential oils inhibited growth of F verticillioides isolates under all conditions tested, but FB₁ production was only inhibited at 30 °C and 0.995 a_w. Moreover, stimulation of toxin production was found under certain environmental conditions. None of the essential oils showed a significantly greater ability to inhibit FB₁ production when compared with the others. At 1000 mg essential oil kg^?1 maize the essential oils showed a greater inhibitory effect on growth of F verticillioides than at 500 mg kg^?1, but there was no difference in FB₁ production between the two levels of essential oil. Copyright © 2004 Society of Chemical Industry     

Mycoflora and fumonisin contamination in Brazilian sorghum from sowing to harvest

BACKGROUND: The aim of this study was to characterise the mycoflora and the presence of fumonisin in sorghum grains, correlating the results with the environment and abiotic factors. RESULTS: Fifty samples (five collections of ten samples each) of sorghum were analysed. All samples were found to be contaminated with fungi, with higher frequencies of Cladosporium spp. (61.8%) and Helminthosporium spp. (33.4%). Fusarium verticillioides was isolated from 15.1% of the samples, with 38% of them being contaminated with fumonisin B₁ (FB₁) at levels ranging from 50 to 368.78 ng g^?1. Regarding abiotic factors, temperature, water activity and rainfall showed a positive correlation with the frequency of F. verticillioides and FB₁ production. There was a significant positive correlation between relative air humidity and FB₁ production. The results obtained from sexual crosses between standard F mating tester strains and the isolated strains confirmed that the strains isolated were F. verticillioides. CONCLUSION: It can be concluded that the decrease in F. verticillioides and fumonisin contamination occurred owing to atypical climatic factors during the period of sorghum cultivation, when there was any occurrence of rain and the level of water activity of grains did not reach 0.58. Copyright © 2010 Society of Chemical Industry     

Review: HPLC determination of fumonisin mycotoxins

An overview of liquid chromatographic methods, mainly employing fluorescence detection together with sample pre-treatment methods, is presented for the determination of the toxic group of fumonisin mycotoxins in various matrices.     

Fatty acid esters of fumonisins: first evidence of their presence in maize

Fumonisin derivatives obtained by esterification of fumonisin B₁ (FB₁) with palmitic, oleic and linoleic fatty acids have been recently described, but never reported in raw maize so far. In this study, the presence of oleoyl-EFB₁ (EFB₁OA) and linoleoyl-EFB₁ (EFB₁LA) in raw maize is reported by means of a suitable LC-ESI-MS/MS method. In addition, the production of EFB₁ derivatives by three Fusarium verticillioides strains is described on malt extract–based media and on corn meal–based growth media. EFB₁OA and EFB₁LA were produced by all considered strains in corn meal medium, with EFB₁LA > EFB₁OA. On the contrary, EFB₁OA and EFB₁LA were never observed in Fusarium cultures grown on a malt extract medium, suggesting that the esterification of FB₁ can occur only in a complex matrix such as maize.     

The effect of delayed harvest on moisture content,insect damage,moulds and aflatoxin contamination of maize in Mayuge district of Uganda

Field drying is a traditional practice carried out by farmers in Uganda and it is one of those practices reported to affect the postharvest quality of maize. A study was therefore conducted to establish the effects of delayed harvest on moisture content, insect damage, moulds and aflatoxin contamination of maize in Mayuge district. Sixteen farmers were selected from Bayitambogwe sub‐county, eight from each of the villages of Bugodi and Musita. Maize was sampled from each farmer's field in 2003B and 2004A seasons at harvest stages of physiological maturity and after delayed harvest for 1, 2, 3 and 4 weeks. Each sample was analysed for mould incidence, moisture content, insect damage and aflatoxin contamination. In each season, mould incidence, insect damage and aflatoxin levels significantly (P < 0.05) increased with delayed time of harvest. Moisture content reduced with delayed harvest time but the maize did not dry to the required safe storage moisture content of ?15%. Seasonal effects were only significant for moisture content: the 2003B crop had consistently lower moisture content than 2004A crop. These results indicate that, for improved harvest quality of maize, farmers should harvest no later than 3 weeks after maize has attained physiological maturity. Copyright © 2005 Society of Chemical Industry