Diversity and metabolomic characterization of Penicillium expansum isolated from apples grown in Argentina and Spain.

Apples (Malus domestica) are one of the most consumed fruits globally. It is a relevant crop in Argentina and Spain, and one of the main fruits for export and industrialization in these countries. Quality control of apples, fundamentally in the postharvest stage, is critical to prevent fungal diseases. The blue mould, caused by Penicillium expansum, is responsible for great economic losses due to the deterioration of the fruit and mycotoxin production. Many studies have characterized this pathogen; however, little is known about the differences between populations from distant geographical origins. The objective of the present study was to characterize two P. expansum populations, from Argentina and Spain, through morphological, metabolomic and molecular approaches, and to evaluate the existence of differences related to their geographical source. A total of 103 isolates, 53 from Argentina and 50 from Spain were studied. Their morphological features were consistent with the species description. The secondary metabolite profiles revealed low chemical diversity. All 103 isolates shared the production of 13 compounds, namely andrastins, aurantioclavine, chaetoglobosins, communesins, expansolides, roquefortine C and patulin. Penostatins and citrinin were produced by 102 and 101 isolates, respectively. A region of the ß-tubulin gene was selected to analyse the diversity of the P. expansum isolates. No substantial differences were observed between isolates of different geographical origins through morphology, patulin accumulation, secondary metabolite profiles and phylogenetic analysis. However, the analysis of polymorphisms revealed 29 haplotypes with a relative separation between isolates of both populations; 13 haplotypes contained Argentinean isolates, while Spanish isolates were separated into 16 haplotypes. The diversity indices of Shannon (H'=2.075; H'=2.402) and Simpson (SiD = 0.850; SiD = 0.895) for isolates from Argentina and Spain, respectively, indicated that the diversity of P. expansum is greater in Spain than in Argentina. This distribution could be explained both by the existence of haplotype exchange between both countries, with the ancestral haplotypes originating in Spain, and the subsequent adaptation to the environmental conditions or apples varieties grown in each region.

Water activity influence on the simultaneous production of DON, 3-ADON and 15-ADON by a strain of Fusarium graminearum ss of 15-ADON genotype.

The influence of aw on DON and its acetyl derivatives biosynthesis by a strain of Fusarium graminearum s.s. (ITEM 4606) which produces DON, 3-ADON and 15-ADON was evaluated. Trichothecene production was studied on agar wheat 2% at 0.95 and 0.99 aw at different temperatures (10, 15, 20, 25 and 30 °C) and incubation times (7, 14, 21 and 28 days). Statistical analysis (ANOVA) showed that aw, temperature, incubation time and their interactions were significant on the production of DON, 3-ADON and 15-ADON (p < 0.0001). The pattern of toxin production was influenced by aw, showing differences for the three toxins. The maximum accumulation of DON occurred at 30 °C at 0.99 aw (14 d) and at 25 °C at 0.95 aw (7 and 21 d). The highest concentration of 3-ADON at 0.95 aw was observed at 25 °C and 7 days, and it was significantly higher than all the other values registered. At 0.99 aw, the maximum occurred at 30 °C and 21 days, but another significantly high accumulation was observed at 28 days at the same temperature. For 15-ADON, at 0.95 aw, the highest amount of toxin was accumulated at 10 °C, both at 7 and 28 days. At 0.99 aw, a maximum was observed at 10 °C and 7 days, significantly different from the values observed at the other conditions. The toxin accumulated at a higher concentration at 0.95 aw was 15-ADON (173.2 µg/g) and at 0.99 aw, 3-ADON (370.6 µg/g). A marked influence of aw on the maximum toxin accumulation with respect to temperature and time was observed for trichothecene production. This is an important fact to consider when designing predictive models to prevent toxin contamination, both in the field and during storage, especially in intermediate drying stages.

Can discrepancies between Fusarium graminearum trichothecene genotype and chemotype be explained by the influence of temperature in the relative production of 3-ADON and 15-ADON?

Wheat is one of the most important crops in Argentina and worldwide. One of the major diseases affecting the crop is the Fusarium Head Blight (FHB). It is an endemic disease caused mainly by Fusarium graminearum, the most common agent of FHB around the world. The infection is strongly influenced by environmental parameters and occurs mostly when there are favourable conditions of moisture and temperature during wheat anthesis or flowering. This destructive disease affects wheat, barley and other small grains and has the capability of destroying crops, causing great economic losses due to reduced grain quality, and the accumulation of significant levels of mycotoxins such as trichothecenes. The aim of this study was to evaluate the influence of temperature on mycotoxin biosynthesis, on three strains of F. graminearum of 15-ADON genotype and one of 3-ADON genotype, with different capacity of synthesizing DON, 3-ADON and 15-ADON. Trichothecene production of the strains at different temperatures (5, 10, 15, 20, 25, 30 and 35 °C) was evaluated after 7, 14, 21, 28 and 35 d of incubation. The optimum temperature to produce DON and 3-ADON was between 25 and 30 °C, but the maximum production of 15-ADON occurred at a lower temperature (10 °C) for all the strains. Conversely, the minimum production of DON and 3-ADON was recorded between 5 and 10 °C and of 15-ADON between 30 and 35 °C. A possible explanation for the similar accumulation of both acetyl derivatives by strains of different chemotype and genotypes could be that the acetyl derivatives biosynthesis is regulated by temperature.

From field to process: How storage selects toxigenic Alternaria spp. causing mouldy core in Red Delicious apples.

Apple is a major crop in Argentina where 50% of the production is derived to by-products. Industries process either recently harvested apples or fruit stored for up to 9 months. This crop is susceptible to fungal diseases both external and internal, such as mouldy core (MC). The incidence of fungal pathogens changes during storage, as well as the risk associated with their presence since some contaminants belong to mycotoxigenic genera. The objective of this study was to characterize the fungal contaminants of Red Delicious apple fruit in Argentina evaluating their evolvement from field to process, with main interest on MC causal agents and mycotoxigenic species. A total of 240 apples were analysed; 140, recently harvested and intended for fresh consumption (C), and 100 stored for 9 months in a refrigerated chamber (0-3 °C) and destined to industrialization (I). The 86% of fresh consumption apples showed external fungal lesions, and only 14% were undamaged; MC incidence was 34%. High biodiversity was observed; Penicillium was the predominant genus (54%), followed by Alternaria spp. (41%). Only 3% of industrialization fruit were undamaged, 48% had external lesions and 51% MC. However, biodiversity was lower in these apples. Alternaria spp. was recovered from 60% of apples, mainly causing MC, while Penicillium spp. took second place (34%). All the Alternaria isolates belonged to Section Alternaria with A. tenuissima as the predominant species-group. Alternariol was synthesised by 75% of the isolates, while both alternariol monomethyl-ether and tenuazonic acid by 76%. From the 100 I apples, 93 were contaminated with at least one of these mycotoxins. Alternaria was the main causal agent of MC in Argentinean Red Delicious apples, and fruit affected by this disease might be incorporated into the process line, with a consequent risk of mycotoxin contamination in apple by-products.

Effects of Fusarium graminearum and Fusarium poae on disease parameters, grain quality and mycotoxins contamination in bread wheat (Part I).

BACKGROUND: Wheat is the most important winter crop in the world, being affected by the presence of fungal, mainly those belonging to the Fusarium genus. Fusarium head blight (FHB) is a serious disease that causes important economic damage and quantitative/qualitative losses, with Fusarium graminearum and Fusarium poae being two of the most isolated species worldwide. The present study aimed to evaluate the interaction between F. graminearum and F. poae and the effects on disease parameters, grain quality and mycotoxin contamination on five wheat genotypes under field conditions during three growing seasons. RESULTS: Statistical differences between Fusarium treatments were found for disease parameters, grain quality and mycotoxin contamination during the 2014/2015 growing season. High values of incidence (58.00 ± 8.00%), severity (6.28 ± 1.51%) and FHB index (4.72 ± 1.35) were observed for F. graminearum + F. poae treatment. Regarding grain quality, the results showed that the degradation of different protein fractions depends on each Fusarium species: glutenins were degraded preferably by F. graminearum (-70.82%), gliadins were degraded preferably by F. poae (-29.42%), whereas both protein fractions were degraded when both Fusarium species were present (-60.91% and -16.51%, respectively). Significant differences were observed for mycotoxin contamination between genotypes, with Proteo being the most affected (DON = 12.01 ± 3.67 µg g-1 ). In addition, we report that 3-ADON predominated over 15-ADON in the three seasons evaluated. CONCLUSION: Variations in plant-pathogen interaction (Fusarium-wheat pathosystem) should be considered at least in years with favorable climatic conditions for FHB development, as a result of the potential impact of this disease on grain quality and mycotoxin contamination. © 2019 Society of Chemical Industry.

Effect of moisture on wheat grains lipid patterns and infection with Fusarium graminearum.

Suitable conditions of temperature and humidity are required to maintain wheat grains quality, but during processing and storage, the grains can be exposed to adverse environmental conditions and presence of infectious fungi. Fusarium graminearum, the main causal agent of Fusarium head blight on wheat, affects crop yields and grain quality by alteration of their biochemical components and mycotoxin contamination, which reduces the possibilities of wheat end use and compromises food safety. Lipid degradation by hydrolytic, oxidative and microbial deterioration is the predominant cause of the loss of sensory acceptability, nutritional value and baking quality. The aim of this research was to determine the influence of adverse environmental conditions -as the increasing moisture - on lipid patterns of whole wheat flours contaminated with F. graminearum in relation to the infection degree. In vitro cultures of F. graminearum were carried out on wheat grains under different degrees of relative humidity (11, 50, 75 and 100%) throughout 45 days of incubation at 28 °C. The fungal biomass measured by q-PCR increased proportionally with the humidity. A decrease in the signals of saturated (palmitic and estearic) and unsaturated (oleic, linoleic and linolenic) fatty acids, analyzed as fatty acid methyl esters (FAMEs) by GC-MS, was observed in relation with the humidity and infection degree. The degradation rate of the lipids was high during the first 15 days of incubation, reaching the fatty acids content, values around 20-40% of those found in the control. From that moment on, the rate of degradation was slower or even null. It was observed that in all treatments, the linolenic acid reached the highest degradation ratio in comparison with the other fatty acids, which may be caused by the action of lipoxygenases. The lipase activity and the content of deoxynivalenol were also determinate on the flours. The lipase activity increased until day 25 of incubation reaching twice the initial value. The deoxynivalenol content also increased along incubation while fatty acids decreased. Our results demonstrated that the magnitude in the signal of fatty acids in whole wheat flours varied in relation to the degree of humidity and fungal infection of the grains from which they were obtained. Otherwise, lipids and their oxidation products are related with the pathogenesis and production of mycotoxins. These observations highlight the importance of an adequate manipulation of wheat grains on the processing chain to prevent quality changes and mycotoxins contamination.

Natural occurrence of mycotoxins and toxigenic capacity of Alternaria strains from mouldy peppers.

Sweet pepper (Capsicum annuum) is an important crop cultivated worldwide, with Argentina being one of the major producers in South America. The fruit is susceptible to several fungal diseases, leading to severe economic losses for producers. In this study, Alternaria was found as the prevalent genus in mouldy peppers (50% fruits infected). Morphological identification revealed that all 64 Alternaria isolates belonged to small-spored species, most of them corresponding to A. tenuissima, A. arborescens and A. alternata species-groups. Their secondary metabolite profile was evaluated in vitro; alternariols were synthesized by most of the isolates (91% for alternariol and 92% for alternariol monomethyl ether). A high number of Alternaria spp. also produced tenuazonic acid (64%), altenuene (84%) and tentoxin (72%). In addition, damaged pepper fruits were analysed for the presence of tenuazonic acid and alternariols. A total 32 out of 48 spoiled pepper fruits were contaminated with at least one of these metabolites. Half of the samples were positive for tenuazonic acid (range 8-11,422µg/kg), while alternariol and its monomethyl ether were less frequently detected (21 and 29%, respectively) and at lower concentrations. This is the first report on the natural occurrence of Alternaria mycotoxins in Argentinean sweet pepper, and highlights a consumer risk when mouldy fruits are used in industrialized products because these compounds are not destroyed by conventional heat treatments.

Characterization of Alternaria strains from Argentinean blueberry, tomato, walnut and wheat.

Alternaria species have the ability to produce a variety of secondary metabolite, which plays important roles in food safety. Argentina is the second largest exporter of fresh and processed food products to Europe, however, few studies on Alternaria mycotoxins and other bioactive secondary metabolites have been carried out on Argentinean cereals, fruit and vegetables. Knowing the full chemical potential and the distribution of Alternaria spp. on crops, it is necessary to establish a toxicological risk assessment for food products for human consumption. In the present study, 87 Alternaria strains from different substrates (tomato, wheat, blueberries and walnuts) were characterized according to morphology and metabolite production. Aggressive dereplication (accurate mass, isotopic patterns and lists of all described compounds from Alternaria) was used for high-throughput evaluation of the chemical potential. Four strains belonged to the Alternaria infectoria sp.-grp., 6 to the Alternaria arborescens sp.-grp., 6 showed a sporulation pattern similar to that of "M" according to Simmons, 1 to that of Alternaria vaccinii, and the remaining 70 constituted a diverse group belonging to morphological groups "G" and "H". The cluster analysis yielded 16 almost identical dendrograms and grouped the Alternaria strains into four clusters and 11 singletons and outlier groups. The chemical analysis showed that AOH and AME were the most common metabolites produced, followed by TEN, ALXs and TeA. The A. infectoria sp.-grp. had no metabolites in common with the rest of the strains. Several secondary metabolites isolated from large-spored Alternaria species or other fungal genera were detected, such as dehydrocurvularin, pyrenochaetic acid and alternarienonic acid. The strains isolated from tomato produced lower amounts of metabolites than strains from blueberries, walnut and wheat, although individual strains from tomato produced the highest amount of some metabolites. The A. infectoria sp.-grp. was unique to cereals, whereas strains classified as belonging to the A. arborescens sp.-grp or having sporulation pattern "M" were only isolated from tomatoes. Otherwise, no clear association between substrate and identity could be found. The analyses in the study show that at least 75% of the Argentinean strains are able to produce potential mycotoxins.

Water activity and temperature effects on growth of Alternaria arborescens on tomato medium.

Alternaria arborescens is the causal agent of tomato stem canker, a disease frequently responsible of substantial economic losses. A. arborescens can produce several mycotoxins, such as alternariol, alternariol monomethyl ether and tenuazonic acid and phytotoxins such as the AAL toxins. The objective of this study was to determine the effect of water activity (aw, 0.950, 0.975, 0.995) and temperature (6, 15, 20, 25 and 30°C) on the germination and radial growth rate of A. arborescens on a synthetic tomato medium. Germination followed by growth was observed at all temperatures and aw levels analyzed. The shortest germination time (0.5 days) was observed at 0.995 aw, both at 25°C and at 30°C. The germination time increased with a reduction of aw and temperature. The highest growth rate was registered at 0.995 aw and 30°C (7.21 mm/day) while the lowest occurred at 0.950 aw and 6°C (0.52 mm/day), conditions at which the longest lag phase was observed (8 days). Growth rates increased with aw and temperature. Knowledge of the ecophysiology of the fungus in this substrate is necessary to formulate future strategies to prevent its development and evaluate the consumer health risk posed by potential exposure to the toxins.

Determinación de perfiles de producción de metabolitos secundarios característicos de especies del género Alternaria aisladas de tomate / Determination of the profiles of secondary metabolites characteristic of Alternaria strains isolated from tomato

Antecedentes. Muchas especies de Alternaria han sido estudiadas por su capacidad de producir metabolitos secundarios bioactivos como la tentoxina (TEN), algunos de los cuales tienen propiedades tóxicas. Las principales toxinas de Alternaria contaminantes de alimentos son el ácido tenuazónico, el alternariol (AOH), el alternariol monometil éter (AME), el altenueno y las altertoxinas i , ii y iii . Objetivos. Determinar los perfiles de metabolitos secundarios característicos de cepas de Alternaria aisladas de tomate para su clasificación quimiotaxonómica. Métodos. Los perfiles de metabolitos secundarios se determinaron por HPLC-MS. Resultados. Los aislamientos de Alternaria obtenidos a partir de tomates con «enmohecimiento negro» pertenecen, según sus características morfológicas, a los grupos especie Alternaria alternata, Alternaria tenuissima y Alternaria arborescens, siendo A. tenuissima el más frecuentemente aislado. Se determinaron los perfiles más característicos de metabolitos secundarios de los grupos especie A. alternata (AOH, AME, TEN), A. tenuissima (AOH, AME, TEN, ácido tenuazónico) y A. arborescens (AOH, AME, TEN, ácido tenuazónico), siendo algunas cepas de este último grupo especie capaces de sintetizar toxinas AAL. Conclusiones. Los perfiles de producción de metabolitos secundarios son una herramienta útil para la diferenciación de aislamientos de Alternaria pertenecientes a grupos especie de esporas pequeñas difícilmente identificables por sus características morfológicas (AU)

Background. Many Alternaria species have been studied for their ability to produce bioactive secondary metabolites, such as tentoxin (TEN), some of which have toxic properties. The main food contaminant toxins are tenuazonic acid, alternariol (AOH), alternariol monomethyl ether (AME), altenuene, and altertoxins i, ii and iii. Aims. To determine the profiles of secondary metabolites characteristic of Alternaria strains isolated from tomato for their chemotaxonomic classification. Methods. The profiles of secondary metabolites were determined by HPLC MS. Results. The Alternaria isolates obtained from spoiled tomatoes belong, according to their morphological characteristics, to the species groups Alternaria alternata, Alternaria tenuissima and Alternaria arborescens, with A. tenuissima being the most frequent. The most frequent profiles of secondary metabolites belonging to the species groups A. alternata (AOH, AME, TEN), A. tenuissima (AOH, AME, TEN, tenuazonic acid) and A. arborescens (AOH, AME, TEN, tenuazonic acid) were determined, with some isolates of the latter being able to synthesize AAL toxins. Conclusions. Secondary metabolite profiles are a useful tool for the differentiation of small spored Alternaria isolates not easily identifiable by their morphological characteristics (AU)

[Determination of the profiles of secondary metabolites characteristic of Alternaria strains isolated from tomato]. / Determinación de perfiles de producción de metabolitos secundarios característicos de especies del género Alternaria aisladas de tomate.

BACKGROUND: Many Alternaria species have been studied for their ability to produce bioactive secondary metabolites, such as tentoxin (TEN), some of which have toxic properties. The main food contaminant toxins are tenuazonic acid, alternariol (AOH), alternariol monomethyl ether (AME), altenuene, and altertoxins i, ii and iii. AIMS: To determine the profiles of secondary metabolites characteristic of Alternaria strains isolated from tomato for their chemotaxonomic classification. METHODS: The profiles of secondary metabolites were determined by HPLC MS. RESULTS: The Alternaria isolates obtained from spoiled tomatoes belong, according to their morphological characteristics, to the species groups Alternaria alternata, Alternaria tenuissima and Alternaria arborescens, with A. tenuissima being the most frequent. The most frequent profiles of secondary metabolites belonging to the species groups A. alternata (AOH, AME, TEN), A. tenuissima (AOH, AME, TEN, tenuazonic acid) and A. arborescens (AOH, AME, TEN, tenuazonic acid) were determined, with some isolates of the latter being able to synthesize AAL toxins. CONCLUSIONS: Secondary metabolite profiles are a useful tool for the differentiation of small spored Alternaria isolates not easily identifiable by their morphological characteristics.

Application of plant derived compounds to control fungal spoilage and mycotoxin production in foods.

Food decay by spoilage fungi causes considerable economic losses and constitutes a health risk for consumers due to the potential for fungi to produce mycotoxins. The indiscriminate use of synthetic antifungals has led to the development of resistant strains which has necessitated utilization of higher concentrations, with the consequent increase in toxic residues in food products. Numerous studies have demonstrated that plant extracts contain diverse bioactive components that can control mould growth. The metabolites produced by plants are a promising alternative because plants generate a wide variety of compounds, either as part of their development or in response to stress or pathogen attack. The aim of this article is to summarize the results from the literature on in vitro and in vivo experiments regarding the effects of plant-derived products for controlling fungal growth. Data from research work on the mode of action of these metabolites inside the fungal cell and the influence of abiotic external factors such as pH and temperature are also covered in the present review. Furthermore, an analysis on how the stress factor derived from the presence of plant extracts and essential oils affects secondary metabolism of the fungus, specifically mycotoxin synthesis, is developed. Finally, the effectiveness of using plant-derived compounds in combination with other natural antimicrobials and its application in food using novel technologies is discussed.

Fungal diversity and natural occurrence of fusaproliferin, beauvericin, deoxynivalenol and nivalenol in wheat cultivated in Santa Fe Province, Argentina.

The Fusarium diversity and the mycobiota associated with moldy wheat kernels from Santa Fe province, Argentine, was assessed. The wheat cultivated area in Santa Fe province is divided according to agrometeorological conditions into two zones: Zone I (north-central) and Zone II (south). The natural occurrence of Fusarium toxins BEA, FUP, DON and NIV was also determined. Cladosporium was the most abundant of the 19 genera identified, followed by Fusarium, Phoma and Alternaria. Zone II shows a predominance of F. graminearum and F. culmorum. In Zone I, DON was present in 13/32 samples (range 0.43-3.60 mg kg(-1)) and NIV in 6/32 samples (range 0.11-0.40 mg kg(-1)). In zone II, DON was found in 11/21 samples (range 0.57-9.50 mg kg(-1)) and NIV in 4/21 samples (range 0.10-0.60 mg kg(-1)). BEA and FP were not detected in both zones.

Effect of processing for saponin removal on fungal contamination of quinoa seeds (Chenopodium quinoa Willd.).

Incidence of fungal contamination of quinoa seeds from three locations (Salar de Uyuni, Bolivia; Salta and Tucumán provinces, Argentina) was analyzed in samples with and without treatment to remove saponins (wet method). In processed samples, the percentage of infection was reduced. Distribution of the different fungal genera was not homogeneous in the three locations (p<0.05), although Penicillium and Aspergillus were the most prevalent contaminants, regardless the geographic origin of the samples. Other genera, such as Eurotium, Fusarium, Phoma, Ulocladium, Mucor and Rhizopus were less frequently isolated. Absidia, Alternaria, Cladosporium, Dreschlera, Epicoccum and Monascus were sporadically encountered. Significant differences (p<0.05) in the distribution of fungal genera in samples with and without saponins from each location were observed. In all cases, processing caused a decrease of Aspergillus incidence, while increased the proportion of Penicillium, Eurotium, Mucor and Rhizopus indicating that these genera were part of the internal mycota. A. flavus and A. niger were the dominating species of genus Aspergillus. A similar pattern of prevalent Penicillium species was observed in samples with and without saponins, since P. aurantiogriseum, P.chrysogenum, P. citrinum and P. crustosum were always present in high number, although their relative density was variable according to the geographic origin of samples. Mycotoxin-producing ability of most representative species was also determined. Toxigenic strains of A. flavus (aflatoxins and cyclopiazonic acid), A. parasiticus (aflatoxins), P. citrinum (citrinin) and P. griseofulvum (cyclopiazonic acid) were found. None of the A. niger isolates was ochratoxin A producer. The above mentioned mycotoxins were not detected in the samples analyzed.

[Putative mycotoxin-producing fungi isolated from alpataco (Prosopis flexuosa) fruits]. / Hongos toxicogénicos contaminantes de frutos de alpataco.

Fungi contaminant of alpataco (Prosopis flexuosa) fruits from La Pampa province (Argentina) were identified. Alternaria alternata and Sphaeropsis sapinea were the dominant species. Phoma sp., Nigrospora sp., Preussia minima, Cladosporium sp., Pithomyces chartarum, Epicoccum nigrum, Aspergillus niger and Aspergillus speluneus were also isolated but with less frequency. Twelve strains of Alternaria alternata, the toxigenic species with higher incidence, were screened for alternariol (AOH), alternariol monomethyl ether (AME) and tenuazonic acid (TA) production. Since one isolate was able to produce AME, six isolates produced AOH and AME and two isolates produced AOH, AME and TA, these results indicate a potential risk of contamination with Alternaria toxins in this substrate.

Hongos toxicogénicos contaminantes de frutos de alpataco / Putative mycotoxin-producing fungi isolated from “alpataco” (Prosopis flexuosa) fruits

Se estudió la presencia de hongos potencialmente toxicogénicos en frutos dealpataco (Prosopis flexuosa D.C. var. depressa Roig) recolectados en laprovincia de La Pampa, Argentina. Las especies predominantes fueronAlternaria alternata y Sphaeropsis sapinea. En menor proporción se aislaronPhoma sp., Nigrospora sp., Preussia minima, Cladosporium sp., Pithomyceschartarum, Epicoccum nigrum, Aspergillus niger y Aspergillus speluneus.La capacidad para producir micotoxinas se determinó en 12 cepas deAlternaria alternata, única especie potencialmente toxicogénica aislada conrelativa frecuencia. Dos cepas produjeron ácido tenuazónico (AT), alternariol(AOH) y alternariol-metil-éter (AME), seis produjeron AOH y AME, una produjosolamente AME y las tres restantes resultaron no toxicogénicas. Losresultados de este estudio preliminar indican un riesgo potencial decontaminación con toxinas de Alternaria en la harina de alpataco, de crecienteuso en la alimentación humana y animal en ciertas áreas geográficas(AU)

Fungi contaminant of “alpataco” (Prosopis flexuosa) fruits from “La Pampaprovince” (Argentina) were identified. Alternaria alternata and Sphaeropsissapinea were the dominant species. Phoma sp., Nigrospora sp., Preussiaminima, Cladosporium sp., Pithomyces chartarum, Epicoccum nigrum,Aspergillus niger and Aspergillus speluneus were also isolated but with lessfrequency. Twelve strains of Alternaria alternata, the toxigenic species withhigher incidence, were screened for alternariol (AOH), alternariol monomethylether (AME) and tenuazonic acid (TA) production. Since one isolate was ableto produce AME, six isolates produced AOH and AME and two isolatesproduced AOH, AME and TA, these results indicate a potential risk ofcontamination with Alternaria toxins in this substrate(AU)

Conditions that regulate the growth of moulds inoculated into bottled mineral water.

The influence of different storage conditions (temperature, illumination, brand of mineral water and storage time) on growth of mould spores was studied. Alternaria alternata, Penicillium citrinum and Cladosporium cladosporioides spores were inoculated in bottles of mineral and mineralised water, packaged in polyethylene terephtalate (PET). The bottles were incubated under different storage conditions. The strains had been isolated from bottled mineral water in a previous study. Storage time was the parameter that had the most important influence in mould growth. The spores grew into visible colonies after 5 month of incubation in bottles just filled, and in a month in bottles that had been stored for 5 month. This could be due to the migration of compounds from PET packaging material into mineral water. This compounds could be used as nutrients (organic matter) for mould growth. The plasticizer additive di-n-butyl phthalate (DBP) concentration in recently bottled mineral water and in 5-month stored bottles was measured. An increase of 20% of DBP concentration was observed. A. alternata and P. citrinum strains were toxicological characterised. Both strains produced mycotoxins in vitro, and P. citrinum produced citrinin in mineral water, posing a potential health risk for consumers.

Variability of aflatoxin and cyclopiazonic acid production by Aspergillus section flavi from different substrates in Argentina.

Aspergillus section flavi strains isolated from peanuts, wheat and soybean grown in Argentina were screened for aflatoxins (type B and G) and cyclopiazonic acid (CPA) production. Aspergillus flavus was the predominant species in all substrates, although there was almost the same proportion of A. flavus and Aspergillus parasiticus in peanuts. Aspergillus nomius was not found. Incidence of aflatoxigenic A. flavus strains was higher in peanuts (69%) than in wheat (13%) or soybeans (5%) while the ratio of CPA producers A. flavus isolated from all substrates was very high (94% in peanuts, 93% in wheat and 73% in soybeans). Isolates of A. flavus able to produce simultaneously aflatoxins type B and CPA were detected in all substrates, suggesting the possibility of co-occurrence of these toxins. Almost all isolates of A. parasiticus resulted aflatoxins (type B and G) producers but did not produce CPA. Five of sixty-seven strains isolated from peanuts showed an unusual pattern of mycotoxin production (aflatoxins type B and G simultaneously with CPA). These strains also produced numerous small sclerotia like S strains of A. flavus detected in cottonseed in Arizona and in soils of Thailand and West Africa. The atypical strains are not widely distributed in Argentina and were found uniquely in peanuts.

Aflatoxin Production in Soybean Varieties Grown in Argentina.

Natural occurrence of aflatoxin contamination on soybeans was investigated. Thirty four samples from the 1986 crop (5.8% positive samples) and 60 samples harvested in 1987 (11.6% positive samples) were analyzed. Aflatoxin levels in positive samples were low, ranging from traces to 36 µg/kg of total aflatoxins. Aflatoxin production by three isolates of Aspergillus flavus / A. parasiticus in 13 soybean varieties has been studied. Soybeans used for cultures were surface disinfected. Levels of aflatoxin formed were dependent both on the toxicogenic potential of the fungal isolate and on the variety of soybeans. Under laboratory conditions variety Prata was the most susceptible and variety SRF the less susceptible to aflatoxin formation.