Phylogenomic Analysis of a 55.1-kb 19-Gene Dataset Resolves a Monophyletic Fusarium that Includes the Fusarium solani Species Complex

Scientific communication is facilitated by a data-driven, scientifically sound taxonomy that considers the end-user's needs and established successful practice. In 2013, the Fusarium community voiced near unanimous support for a concept of Fusarium that represented a clade comprising all agriculturally and clinically important Fusarium species, including the F. solani species complex (FSSC). Subsequently, this concept was challenged in 2015 by one research group who proposed dividing the genus Fusarium into seven genera, including the FSSC described as members of the genus Neocosmospora, with subsequent justification in 2018 based on claims that the 2013 concept of Fusarium is polyphyletic. Here, we test this claim and provide a phylogeny based on exonic nucleotide sequences of 19 orthologous protein-coding genes that strongly support the monophyly of Fusarium including the FSSC. We reassert the practical and scientific argument in support of a genus Fusarium that includes the FSSC and several other basal lineages, consistent with the longstanding use of this name among plant pathologists, medical mycologists, quarantine officials, regulatory agencies, students, and researchers with a stake in its taxonomy. In recognition of this monophyly, 40 species described as genus Neocosmospora were recombined in genus Fusarium, and nine others were renamed Fusarium. Here the global Fusarium community voices strong support for the inclusion of the FSSC in Fusarium, as it remains the best scientific, nomenclatural, and practical taxonomic option available.

Evaluation of behaviour of Lachancea thermotolerans biocontrol agents on grape fermentations

Previous researches have showed that Lachancea thermotolerans strains RCKT4 and RCKT5 inhibited the growth of Aspergillus. However, currently, there are no data on their nutritional preferences, as a possible substrate competitor against Saccharomyces cerevisiae, and their effects on fermentation. In this work, we observed that the biocontrol yeasts and S. cerevisiae BSc203, based on the utilization of 16 carbonate sources, revealed significant differences in the nutritional profile (biocontrol yeasts NS:0·25, BSc203 NS:0·56). Lachancea thermotolerans strains did not occupy the same niche as that of BSc203 (NOI:0·44). The biocontrol agents and BSc203 presented similar competitive attitude in terms of the sugar, ethanol and sulphite tolerances. During fermentation, the biocontrol yeasts were found to tolerate up to 12% v/v ethanol, 250 mg ml^-1 of total SO₂ and 30° Brix sugar. In mixed cultures, L. thermotolerans strains did not negatively affect the growth of BSc203 and the wine quality, except when RCKT4 was initially inoculated at a high proportion in the mixed culture 1MSK4 (1%BSc203/99%RCKT4), resulting in a lower production of CO₂ and ethanol, in comparison with pure BSc203. RCKT5, at a high proportion, in 1MSK5 (1%BSc203/99%RCKT5) presented promising oenological properties. This fermentation showed lower acetic acid contents and higher total acidity than pure BSc203.

SIGNIFICANCE AND IMPACT OF THE STUDY

Generally it is not evaluated if the biofungicide yeasts sprayed on vegetables alter the quality of the fermented products. This work focused on the importance of assessing the possible effects of yeast-based fungicides used in vineyards on grape fermentation, especially on Saccharomyces cerevisiae growth. In this context, the competition between biofungicide yeasts and S. cerevisiae under winemaking conditions is investigated.

The Mycotox Charter: Increasing Awareness of, and Concerted Action for, Minimizing Mycotoxin Exposure Worldwide

Mycotoxins are major food contaminants affecting global food security, especially in low and middle-income countries. The European Union (EU) funded project, MycoKey, focuses on “Integrated and innovative key actions for mycotoxin management in the food and feed chains” and the right to safe food through mycotoxin management strategies and regulation, which are fundamental to minimizing the unequal access to safe and sufficient food worldwide. As part of the MycoKey project, a Mycotoxin Charter (charter.mycokey.eu) was launched to share the need for global harmonization of mycotoxin legislation and policies and to minimize human and animal exposure worldwide, with particular attention to less developed countries that lack effective legislation. This document is in response to a demand that has built through previous European Framework Projects—MycoGlobe and MycoRed—in the previous decade to control and reduce mycotoxin contamination worldwide. All suppliers, participants and beneficiaries of the food supply chain, for example, farmers, consumers, stakeholders, researchers, members of civil society and government and so forth, are invited to sign this charter and to support this initiative.

Biocontrol of Fusarium graminearum sensu stricto, Reduction of Deoxynivalenol Accumulation and Phytohormone Induction by Two Selected Antagonists

Fusarium head blight (FHB) is a devastating disease that causes extensive yield and quality losses to wheat and other small cereal grains worldwide. Species within the Fusarium graminearum complex are the main pathogens associated with the disease, F. graminearum sensu stricto being the main pathogen in Argentina. Biocontrol can be used as part of an integrated pest management strategy. Phytohormones play a key role in the plant defense system and their production can be induced by antagonistic microorganisms. The aims of this study were to evaluate the effect of the inoculation of Bacillus velezensis RC 218, F. graminearum and their co-inoculation on the production of salicylic acid (SA) and jasmonic acid (JA) in wheat spikes at different periods of time under greenhouse conditions, and to evaluate the effect of B. velezensis RC 218 and Streptomyces albidoflavus RC 87B on FHB disease incidence, severity and deoxynivalenol accumulation on Triticum turgidum L. var. durum under field conditions. Under greenhouse conditions the production of JA was induced after F. graminearum inoculation at 48 and 72 h, but JA levels were reduced in the co-inoculated treatments. No differences in JA or SA levels were observed between the B. velezensis treatment and the water control. In the spikes inoculated with F. graminearum, SA production was induced early (12 h), as it was shown for initial FHB basal resistance, while JA was induced at a later stage (48 h), revealing different defense strategies at different stages of infection by the hemibiotrophic pathogen F. graminearum. Both B. velezensis RC 218 and S. albidoflavus RC 87B effectively reduced FHB incidence (up to 30%), severity (up to 25%) and deoxynivalenol accumulation (up to 51%) on durum wheat under field conditions.

Evaluation of zearalenone, α-zearalenol, β-zearalenol, zearalenone 4-sulfate and β-zearalenol 4-glucoside levels during the ensiling process

Zearalenone-producing Fusarium species can contaminate maize before ensiling and cause reproductive problems in animals. Suspect feeds are only routinely analysed for zearalenone (ZEA), not considering other oestrogenic metabolites or masked derivatives. The aims of the present study were to monitor the levels of ZEA, α-zearalenol (α-ZOL), β-zearalenol (β-ZOL), zearalenone-4-sulfate (ZEA-4S) and β-zearalenol-4-glucoside (β-ZOL-4G) in artificially contaminated maize silage and determine the effect of the ensiling process on these toxins. A laboratory silo model was designed using polystyrene bags filled with previously contaminated chopped whole-plant maize, stored in a dry and cool room and sampled at days 7, 45, 90, 120 and 127. ZEA, α-ZOL, β-ZOL, ZEA-4S and β-ZOL-4G levels were quantified by liquid chromatography – tandem mass spectrometry. Chemical and physical analysis indicated silage maintained good quality in all stages. pH was reduced favourably (P<0.05) from 4.69 to 3.80 during the preservation stage. Dry matter, moisture content and water activity did not vary from day 7 to 127. ZEA, α-ZOL, β-ZOL and ZEA-4S levels also did not change from day 7 to 127, indicating no significant degradation by the ensiling process or silage-native microbiota. This study suggests that ZEA levels remain invariable during the ensiling process, as well as the levels of its derivatives. The presence of highly oestrogenic metabolites, like α-ZOL and the masked ZEA-4S, which are not screened in the routine analyses, increases the overall toxicity of ZEA-contaminated silage.

One fungus, one name: defining the genus Fusarium in a scientifically robust way that preserves longstanding use

In this letter, we advocate recognizing the genus Fusarium as the sole name for a group that includes virtually all Fusarium species of importance in plant pathology, mycotoxicology, medicine, and basic research. This phylogenetically guided circumscription will free scientists from any obligation to use other genus names, including teleomorphs, for species nested within this clade, and preserve the application of the name Fusarium in the way it has been used for almost a century. Due to recent changes in the International Code of Nomenclature for algae, fungi, and plants, this is an urgent matter that requires community attention. The alternative is to break the longstanding concept of Fusarium into nine or more genera, and remove important taxa such as those in the F. solani species complex from the genus, a move we believe is unnecessary. Here we present taxonomic and nomenclatural proposals that will preserve established research connections and facilitate communication within and between research communities, and at the same time support strong scientific principles and good taxonomic practice.

Effect ofTrichoderma species on growth of Fusariumproliferatiom and production of fumonisins, fusaproliferin and beauvericin

Trichoderma species has been suggested as potential biocontrol agent forFusarium verticillioides on maize. In this cereal,F. verticillioides and F. proliferatum contributed to fumonisin accumulation. In addition,F. proliferatum could produce beauvericin and fusaproliferin.The aim of this work was to evaluate the effect ofTrichoderma spp. on growth and fumonisin B(1) fusaproliferin and beauvericin production byF. proliferatum.Dual cultures of F.proliferatum andT. harzianum ITEM 3636 andT. longibrachiatum ITEM 3635 on maize meal agar at 0.995 aw were done. The effect ofTrichoderma spp. on the lineal growth ofF. proliferatum was determined. The effect ofTrichoderma species on fumonisin B(1), fusaproliferin and beauvericin production byF. proliferatum was determined on co-inoculated maize kernels by HPLC.T. harzianum suppressedF. proliferatum growth once contact between the colonies occurred.T. longibrachiatum showed a less antagonistic effect againstF. proliferatum. A reduction on fumonisin B(1) production of 98% and 88% was observed in the co-incubation ofF. proliferatum withT. harzianum andT. longibrachiatum, respectively. The decrease of FB(1) production was significant even in maize kernels on whichF. proliferatum had been growing 7 days prior to the addition ofTrichoderma spp. The concentration of beauvericin and fusaproliferin produced during 30 days coincubation ofF. proliferatum with bothTrichoderma spp. did not differ to those produced byF. proliferatum alone. These mycotoxins might enter the food chain causing so far unknown consequences to the health of domestic animals and humans. For this reason it is important, when a potential biocontrol agent is under study, to test the effect on the fungal growth and on the putative mycotoxin produced.

Trichothecenes and zearalenone production by Fusarium equiseti and Fusarium semitectum species isolated from Argentinean soybean

Fusarium equiseti and Fusarium semitectum represent the most abundant species in the Fusarium complex isolated from flowers, soybean pods and seeds in Argentina. The aim of the present study was to assess the production of major type A and type B trichothecenes (diacetoxyscirpenol, neosolaniol, T-2 toxin and HT-2 toxin, nivalenol, deoxynivalenol) and zearalenone by 40 F. equiseti and 22 F. semitectum isolates on rice culture. Mycotoxins were determined by HPLC with fluorescence detection after derivatisation with 1-anthronylnitrile for type A trichothecenes (i.e. diacetoxyscirpenol, neosolaniol, T-2 toxin and HT-2 toxin), by HPLC with UV detection for type B trichothecenes (i.e. nivalenol and deoxynivalenol), and by TLC for zearalenone. A total of 22 of 40 F. equiseti isolates produced diacetoxyscirpenol, nivalenol and ZEA alone or in combination, whereas only two of 20 F. semitectum isolates were nivalenol and ZEA producers. Both Fusarium species did not produce any deoxynivalenol, neosolaniol, T-2 toxin and HT-2 toxin. The variable retention in toxigenicity displayed by both fungal species suggests that these species have a saprophytic lifestyle in the soybean agroecosystem in Argentina.

Statistical optimization of simple culture conditions to produce biomass of an ochratoxigenic mould biocontrol yeast strain

AIM

  To maximize biomass production of an ochratoxigenic mould-controlling strain of Lachancea thermotolerans employing response surface methodology (RSM).

METHODS AND RESULTS

  Using Plackett-Burman screening designs (PBSD) and central composite designs (CCD), an optimized culture medium containing (g l(-1) ): fermentable sugars (FS), 139·2, provided by sugar cane molasses (CMz), (NH(4) )(2) HPO(4) (DAP), 9·0, and yeast extract (YE), 2·5, was formulated. Maximal cell concentration obtained after 24 h at 28°C was 24·2 g l(-1) cell dry weight (CDW). The mathematical model obtained was validated in experiments performed in shaken-flask cultures and also in aerated bioreactors. Maximum yield and productivity values achieved were, respectively, of 0·23 g CDW/g FS in a medium containing (g l(-1) ): FS, 87·0; DAP, 7·0; YE, 1·0; and of 0·96 g CDW l(-1) h(-1) in a medium containing (g l(-1) ): FS, 150·8 plus DAP, 6·9.

CONCLUSIONS

  Optimized culture conditions for maximizing yeast biomass production determined in flask cultures were applicable at a larger scale. The highest yield values were attained in media containing relatively low-CMz concentrations supplemented with DAP and YE. Yeast extract would not be necessary if higher productivity is the aim.

SIGNIFICANCE AND IMPACT OF THE STUDY

  Cells of L. thermotolerans produced aerobically could be sustainably produced in a medium just containing cheap carbon, nitrogen and phosphorus sources. Response surface methodology allowed the fine-tuning of cultural conditions.

Natural deoxynivalenol occurrence and genotype and chemotype determination of a field population of the Fusarium graminearum complex associated with soybean in Argentina

Soybean (Glycine max L.), the main source of protein throughout the world, is used both as a food and a feedstuff. Currently, limited information about the occurrence of Fusarium species and mycotoxins in soybean grain and by-products is available. The aims of the present study were: (1) to identify toxigenic Fusarium species associated with soybean during crop reproductive stages; (2) to determine the occurrence of deoxynivalenol (DON) and nivalenol (NIV) in soybean seeds; (3) to determine the genotype and chemotype of selected Fg complex strains using molecular and chemical analysis, respectively; and (4) to characterize the strains using AFLP(s) markers. One soybean field located at Córdoba Province, Argentina, was monitored and samples of soybean tissue were harvested at three reproductive stages: flowering (R2), full seed (R6) and full maturity (R8). A total of 389 Fusarium strains F. equiseti (40%) was the most frequently species recovered followed by F. semitectum (27%) and F. graminearum (Fg) (11%). From the 40 soybean samples analysed, only two presented detectable DON levels. Based on DON occurrence on soybean seeds at ripening stages, the toxigenic ability of Fg complex strains isolated from soybean seeds, pods and flowers were analysed. The trichothecene genotype was determined by a multiplex PCR using primers based on Tri3, Tri5 and Tri7 toxin genes and then the chemotype was verified by chemical analysis. Most Fg complex strains showed 15-ADON genotype and five strains presented a DON/NIV; these also produced both toxins under in vitro culture. Neither the NIV nor the 3-ADON genotypes were detected among the members of the population evaluated. All the 15-ADON genotype strains were characterized as F. graminearum sensu stricto (lineage 7), while the strains presented a DON/NIV genotype were characterized as F. meridionale (lineage 2). The present study contributes new information on the occurrence of Fusarium species and trichothecenes toxins on soybean at the pre-harvest stages. Also, this is the first report on the chemotype, genotype and lineages among Fg complex isolated from soybean.

Survey of T-2 and HT-2 toxins in soybean and soy meal from Argentina using immunoaffinity clean-up and high performance liquid chromatography

Soybean and soy meal samples collected during the harvest season 2008-2009 in the soybean-growing area of Córdoba Province in Argentina were analysed for T-2 and HT-2 toxins occurrence. These mycotoxins were detected using HPLC analysis with fluorescence detection after derivatisation with 1-anthronylnitrile and immunoaffinity column clean-up. Characteristics of in-house validated method such as accuracy, precision, detection and quantification limits were defined by means of recovery test with spiked soybean and soy meal samples. Mean recoveries for T-2 within the spiking range 125-500 µg/kg, were 90.9 and 81.3% for soybean and soy meal, respectively with a withinlaboratory relative standard deviation <10%. Analysis of samples spiked with HT-2 in the same range gave a mean recovery of 70.2 and 77.5% for soybean and soy meal, respectively, with relative standard deviations <12%. The limit of detection for the method was 25 µg/kg for T-2 and HT-2, based on a signal-to-noise ratio 3:1 and the limit of quantification was established as three times the detection limit. Out of 64 samples, only two soybean samples showed contamination with A-type trichothecenes evaluated. Confirmatory analyses of the contaminated samples were performed by LC-MS/MS. This study demonstrated low incidences and levels of T-2 and HT-2 in soybean harvested among the areas in the Cordoba Province.

Fungal and mycotoxin contamination in Bt maize and non-Bt maize grown in Argentina

A Bt maize hybrid and its non-transgenic counterpart harvested during 2002/2003 and 2003/2004 harvest seasons from different locations within the maize-growing area in Argentina were compared for fungal and mycotoxin contamination. Fusarium species were the most prevalent on both genotypes with an isolation frequency >60% across all locations. The percentage of infection was lower in Bt maize than in non-Bt maize (P<0.05). There were no statistical differences in infection percentage due to genotype, fungicide treatment and their interactions. Fumonisins were detected in all of the samples from all locations and genotypes. Total fumonisin levels (fumonisins B1, B2 and B3) in the Bt and the non-Bt hybrid were significantly different (P<0.001), with lower toxin levels in the Bt maize in all locations but one evaluated during the two harvest season. There was no significant difference in deoxynivalenol levels between Bt and non-Bt maize. Application of the fungicide tebuconazole did not alter either the infection or the toxin levels in the Bt and non-Bt maize hybrid.

Deoxynivalenol and nivalenol analysis in soybean and soy flour

A rapid and accurate method of quantifying deoxynivalenol (DON) and nivalenol (NIV) in soybean and soy flour is described. The samples were extracted with acetonitrile:water (84:16, v/v) and cleaned through a solidphase extraction (SPE) column. The mycotoxins were separated, detected and quantified by reversed-phase high performance liquid chromatography (HPLC) with UV detection (220 nm) using water:methanol (88:12, v/v) as mobile phase. Characteristics of this in-house method such as accuracy, precision and detection and quantification limits were defined by means of a recovery test with spiked soybean and soy flour samples. The detection limit (LOD) was 0.1 µg/g for DON and 0.2 µg/g for NIV, based on a signal-noise ratio 3:1. Quantification limit (LOQ) was established as three times the detection limit.

Genetic diversity in Aspergillus parasiticus population from the peanut agroecosystem in Argentina

AIMS

The aims of this work were to identify potential sources of Aspergillus parasiticus inoculum and to evaluate the sclerotial and toxigenic profiles of this species from the peanut agroecosystem in Argentina. Likewise, the genetic diversity of A. parasiticus population was analysed using vegetative compatibility group (VCG) analysis.

METHODS AND RESULTS

The A. parasiticus strains were isolated from soil, debris and peanut seeds in Córdoba Province, Argentina. A. parasiticus was recovered from the three sources analysed. Only 11 of 185 A. parasiticus isolates (5.9%) did not produce aflatoxins, while 57% produced sclerotia. Twenty-four VCG were identified from 63 isolates. The VCG diversity index for A. parasiticus, expressed as the number of groups divided by the total number of isolates, was 0.31. In general, there were significant differences among VCG in aflatoxin production.

CONCLUSIONS

The presence of aflatoxigenic strains of A. parasiticus in the three substrates suggests that they may be an important source of aflatoxin in Argentina's peanut agroecosystem. The A. parasiticus population shows a low genetic diversity.

SIGNIFICANCE AND IMPACT OF THE STUDY

The present study showed data on inoculum distribution, aflatoxin and sclerotia production and genetic diversity in an A. parasiticus population isolated from the peanut agroecosystem in Argentina.

Temperature and water activity effects on growth and temporal deoxynivalenol production by two Argentinean strains of Fusarium graminearum on irradiated wheat grain

The objective of this study was to determine the effects of water activity (a(W); 0.900-0.995), temperature (5, 15, 25 and 30 degrees C), time of incubation (7-49 days) and their interactions on mycelial growth and deoxynivalenol (DON) production on irradiated wheat grain by two strains of Fusarium graminearum isolated from wheat ears in Argentina. Optimal a(W) levels for growth were in the range 0.950-0.995 with a temperature optima of 25 degrees C. Maximum growth rates were obtained at the highest a(W) (0.995) and 25 degrees C for both strains. No growth was observed at 5 degrees C regardless of the a(W) levels assayed. Both strains were able to growth at the lowest a(W) assayed (0.900), although the temperature ranges allowing growth at this minimal a(W) was 15-25 degrees C. DON was produced the most rapidly (7 days) when incubated at 25 degrees C and 0.995 a(W). All other conditions required 7-14 days before DON was produced on grain. Maximum amounts of DON for both strains were produced at the highest a(W) treatment (0.995) after 6 weeks at 30 degrees C. The range of DON concentrations varied considerably (5 to 140,000 ng g(-1)) depending on a(W) and temperature interaction treatments. Production of DON occurred over a narrower range of a(W) (0.995-0.95) than that for growth (0.995-0.90). DON was more rapidly produced at 25 degrees C but the maximum amount produced was at 30 degrees C. Two-dimensional profiles of a(W) x temperature were developed from these data to identify areas where conditions indicate a significant risk from DON accumulation.

Biocontrol of Bacillus subtilis against Fusarium verticillioides in vitro and at the maize root level

Bacillus species as a group offer several advantages over other bacteria for protection against root pathogens because of their ability to form endospores, and because of the broad-spectrum activity of their antibiotics. The objectives of this work were to determine the ability of strains of Bacillus to inhibit Fusarium verticillioides growth and fumonisin B(1) accumulation in vitro, and to evaluate the ability of the best bacterium for preventing rhizosphere and endorhizosphere colonization by F. verticillioides. Bacterial populations from the maize rhizoplane were obtained, and the capacity of ten Bacillus strains to inhibit fungal growth and fumonisin B(1) accumulation in vitro was assayed. According to these results, B. subtilis CE1 was selected as the best antagonist for testing maize root colonization of F. verticillioides. Bacillus subtilis CE1 at 10(8) and 10(7) CFU ml(-1) inocula was able to reduce rhizoplane and endorhizosphere colonization of F. verticillioides in greenhouse trials. The strain B. subtilis CE1 could be a potential biological control agent against F. verticillioides at the root level.

In vitro control of growth and fumonisin production by Fusarium verticillioides and F. proliferatum using antioxidants under different water availability and temperature regimes

AIMS

To examine the effect of butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), trihydroxybutyrophenone and propylparaben (PP) (at concentrations of 1-20 mmol l(-1)) on growth of and fumonisin production by Argentinian strains of Fusarium verticillioides and F. proliferatum.

METHODS AND RESULTS

Studies on lag phases prior to growth, relative growth rates and fumonisin concentrations were carried out in vitro in relation to water activity (0.995-0.93 a(w)) and temperature (18 and 25 degrees C) on a maize meal agar. Overall, PP was the antioxidant which was most effective at inhibiting strains of both species. The lag phase prior to growth and growth rates were significantly decreased by PP and BHA at 10 and 20 mmol l(-1), regardless of the temperature or aw level tested. Total fumonisin production was higher at 0.98 a(w) and decreased by about 45-50% at 0.995 and 0.95 a(w). Overall, BHT only inhibited fumonisin production at 0.95 aw at 10 and 20 mmol l(-1), while BHA was effective at most a(w) levels tested at 10 and 20 mmol l(-1). Propylparaben completely inhibited fumonisin production by both F. verticillioides and F. proliferatum at > 1 mmol l(-1), regardless of the temperature or a(w) level. Small interstrain differences in the levels of inhibition by the antioxidants were observed for three F. verticillioides and four F. proliferatum strains at 0.995, 0.98 and 0.95 a(w). Propylparaben and BHA completely inhibited the growth of both species at the concentrations evaluated, regardless of the a(w) level.

CONCLUSIONS

Two antioxidants show promise for the control of growth of and fumonisin production by these species over a wide range of environmental conditions.

SIGNIFICANCE AND IMPACT OF THE STUDY

Potential exists for using such food-grade preservatives for prevention of mycotoxigenic fungi and their toxins entering the food chain.

In vitro and in vivo studies to assess the effectiveness of cholestyramine as a binding agent for fumonisins

Several adsorbent materials were tested at I mg/ml for their in vitro capacity to adsorb fumonisin B1(FB1) from aqueous solutions. Cholestyramine showed the best adsorption capacity (85% from a solution containing 200 microg/ml FB1) followed by activated carbon (62% FB1). Bentonite adsorbed only 12% of the toxin from a solution containing 13 microg/ml FB1, while celite was not effective even at the lowest tested FB1 concentration (3.2 microg/ml). Cholestyramine was tested in vivo to evaluate its capacity to reduce the bioavailability of fumonisins (FBs) in rats fed diet contaminated with toxigenic Fusarium verticillioides culture material. Rats were exposed for one week to FBs-free diet, FBs-contaminated diet containing 6 or 20 microg/g FB1 + FB2 and the same FBs-contaminated diet added of 20 mg/g cholestyramine. The increase of sphinganine/sphingosine (SA/SO) ratio in urine and kidney of treated rats was used as specific and sensitive biomarker of fumonisin exposure. The addition of cholestyramine to the FBs-contaminated diets consistently reduced the effect of FBs by reducing significantly (P < 0.05) both urinary and renal SA/SO ratios.

Experimental subchronic mycotoxicoses in mice: individual and combined effects of dietary exposure to fumonisins and aflatoxin B1

We have used a murine model of subchronic mycotoxicoses produced by ingestion of mycotoxins. The five groups of animals studied were fed for 30, 60 and 90 days, respectively, with commercial diet (CD), experimental control diet (ECD), experimental with fumonisin B1 diet (EFD) and experimental with mixtures of mycotoxins diet (EMD). The animals fed EFD and EMD showed a significant increase in feed consumption/day with respect to the animals fed ECD (P < 0.005 for both groups). The biochemical measurements showed significant differences at 90 days in those animals fed EAD exhibiting a marked decrease in the values of alkaline phosphatase (ALP) and cholesterol (P < 0.05), along with a significant increase in calcium (P < 0.01). Differences in the decrease of the parameters studied were observed in mice fed EFD for triglycerides, cholesterol and calcium (P < 0.05 for all of them). The activity of aspartate transaminase (AST) increased significantly in animals fed EMD (P < 0.01). The tissue specimens at 60 days showed lesions in the livers of the animals fed EAD and EFD. At 90 days, and in those fed EAD, EFD and EMD, the lesions were intensified in the liver at 60 days in 80, 90 and 100% of the animals, respectively.

Occurrence of Aspergillus section flavi and aflatoxin B1 in corn genotypes and corn meal in Argentina

A study has been carried out in Argentina on samples of corn genotypes from a breeding station as well as in commercially available corn meal. All samples were analyzed for fungal infection and aflatoxin B1. Mycological analysis of corn genotypes showed the presence of three principal genera of filamentous fungi Fusarium (100%), Penicillium (67%) and Aspergillus (60%). In the genus Fusarium three species were identified, F. moniliforme (42%), F. nygamai (56%) and F. proliferatum (1.8%). Eight species of Penicillium were identified, the predominant species isolated were P. minioluteum, P. funiculosum and P. variabile. In the genus ranked third in isolation frequency, two species were identified, A. flavus and A. parasiticus, the percentage of infection was 78% and 21%, respectively. Only one corn genotype was contaminated with aflatoxin B1 at a level of 5 ppb. The corn meal samples showed great differences in fungal contamination, the values ranging from 1 x 10(1) to 7 x 10(5) cfu g-1. Fusarium (68%), Aspergillus (35%) and Penicillium (21%) were the most frequent genera isolated. Among the genus, Aspergillus, A. parasiticus (38%) was the most frequent species isolated. All the samples of corn meal were negative to aflatoxin B1. These results indicate a low degree of human exposure to aflatoxins in Argentina through the ingestion of maize or corn meal.

Effects of food preservatives on Alternaria alternata growth and tenuazonic acid production

The effects of different organic acids on Alternaria alternata growth and tenuazonic acid production (TeA) were evaluated. Both TeA pure toxin solution and TeA production in solid medium were considered. Sodium benzoate, potassium sorbate and sodium propionate, all preservatives commonly used by food industry in Argentina, were tested. TeA was stable as pure toxin solution when was treated with the salts of organic acids used. A differential effect was observed when the preservatives were evaluated in relation to A. alternata growth and TeA production in solid medium. Levels above 10 mg/kg of sodium benzoate and potassium sorbate produced a total inhibition of fungal development and toxin biosynthesis. Sodium propionate produced a 59% decrease in A. alternata growth and total inhibition of TeA production only at the highest concentration of preservatives used.

Microbial interaction ofAspergillus parasiticus andBacillus subtilis withalternaria alternata. production of alternariol, alternariol monomethylether and tenuazonic acid on sunflower seeds

Production of alternariol, alternariol mono-methylether and tenuazonic acid byAlternaría alternata was studied in competition withAspergillus parasiticus andBacillus subtilis on irradiated sunflower seeds at 0.90 aw.In cultures co-inoculated withAlternaría alternata andAspergillus parasiticus alternariol production decreased by 64%. Similar results were observed in cultures co-inoculated withAlternaría alternata andBacillus subtilis.

Production of alternariol and alternariol mono-methyl ether by isolates of Alternaria spp. from Argentinian maize

Alternaria cultures (87 isolates of Alternaria alternata, four of A. tenuissima, two of A. radicina, and three of Alternaria state of Pleospora infectoria respectively, from maize) were screened to determine their ability to produce alternariol (AOH) and alternariol monomethyl ether (AME) on maize and rice. Only 28 A. alternata stains had toxigenic capacity. When maize was used as substrate 21 of 28 isolates produced AOH and AME, and 23 of 28 strains produced AOH and 22 of 28 produced AME when rice was used. The level of AOH produced by the isolates ranged from 0.3 to 2.1 mg/kg on maize and from 0.4 to 9.9 mg/kg on rice. The AME production by the stains ranged between 0.3 and 3.3 mg/kg both on maize and on rice. These results could indicate a low probability of AOH and AME occurring naturally on maize in Argentina.

Occurrence of deoxynivalenol and Fusarium graminearum in Argentinian wheat

During the 1993 harvest period there was a high incidence of Fusarium head blight in wheat in Argentina. Fusarium species that produce trichothecenes in wheat have been reported in several countries including Argentina. Several studies have shown that F. graminerarum and deoxynivalenol (DON) were the main contaminants detected in wheat and by-products in Argentina. The objective of this study was to evaluate the occurrence of Fusarium spp. and DON contamination in wheat from Córdoba, Argentina during the 1993/94 harvest season. F. graminearum was the main Fusarium species isolated. From 40 samples analysed, 80% showed DON contamination. The levels of DON found ranged between 300 and 4500 micrograms/kg. There was good correlation between F. graminearum and DON contamination. Only five samples showed levels of DON higher than those established in the guidelines in Canada and the USA for food and feedstuffs.

Effect of dichlorvos on growth and mycotoxin production by Alternaria alternata

The effect of dichlorvos (DDPV) on growth and alternariol (AOH), alternariol monomethyl ether (AME) and tenuazonic acid (TA) production was evaluated both in culture media and on sunflower seeds. At the levels evaluated of 1 to 600 mg/kg, the insecticide showed a slight effect on the linear growth rate, which was dose dependent, and caused morphological changes in the mycelia and conidia. The pesticide had a remarkable influence on AOH, AME and TA production.

Aflatoxins in sunflower seeds: influence of Alternaria alternata on aflatoxin production by Aspergillus parasiticus

The aim of the present work was to determine the influence of Alternaria alternata upon aflatoxin production by Aspergillus parasiticus. A mixture of spores of both strains was inoculated in sunflower seeds at 0.90 aw and incubated for 42 days at 28 degrees C +/- 1. The cultures were observed and analyzed every 7 days to determine the infection level of the seeds and the production of aflatoxins. Results showed that when the seeds were inoculated only with Aspergillus parasiticus, 100% were infected from the 7th day. When Aspergillus parasiticus and Alternaria alternata were simultaneously inoculated the infection level of the seeds was 100% for Aspergillus parasiticus following 7 days of inoculation and 0% for Alternaria alternata. After the 14th day of inoculation there was no significant difference in the infection percentage of both strains (approximately 80% of each one). As far as toxin production is concerned a remarkable decrease was observed when seeds were inoculated with both strains simultaneously. In accordance to the results, Alternaria alternata would not compete with Aspergillus parasiticus in colonization of seeds but would either degrade the aflatoxins by Aspergillus parasiticus or compete for aflatoxin biosynthesis precursors. Alternaria alternata could also secrete some substance that specifically inhibits aflatoxin synthesis.

Studies on damage to sunflower seeds: water activity, germination, acidity index and aflatoxin B1 presence

The significance of fungal contamination during the storage of sunflower seeds has been investigated. Samples were taken during 7 months at 45 day-intervals. Water activity, seed germination, presence of aflatoxin B1 and free fatty acids were monitored. It was demonstrated that water activity increased during storage, germinability decreased, the content of free fatty acid increased and so did the content of aflatoxin B1.

Aflatoxins in sunflower seeds: effect of zinc in aflatoxin production by two strains of Aspergillus parasiticus

Growth and aflatoxin production by Aspergillus parasiticus NRRL 2999 and Aspergillus parasiticus RC 12 were studied both in sunflower seed and a synthetic culture medium (with and without zinc enrichment). On a synthetic culture medium the strains behaved in different ways according to the zinc concentration. In sunflower seed medium the influence of zinc was not so evident. Thus the results show that the influence of zinc is not the same for different strains and substrates.