Ochratoxigenic moulds and effectiveness of grape field antifungals in a climatic change scenario

BACKGROUND: The presence of ochratoxin A (OTA) in grapes and grape derivatives has been reported mainly in the Mediterranean area. Consequently, great efforts are being made to prevent the growth of Aspergillus on grapes. However, the European Commission suggests that climate change may result in increased temperatures and longer drought periods in southern Europe. Therefore the aim of this study was to investigate how ochratoxigenic fungal growth and the efficiency of fungicides used at present might be affected by environmental conditions predicted with climate change. RESULTS: The effectiveness of grape field antifungals (Switch, Flint Max and Equisetum arvense extract) under two alternating temperature, photoperiod and relative humidity (RH) scenarios (current: 20/30 °C, 16 h light/8 h darkness, 80% RH; predicted: 25/37 °C, 16 h light/8 h darkness, 75% RH) on the growth and OTA production of two Aspergillus carbonarius isolates and one Aspergillus ochraceus isolate on grapes was investigated. CONCLUSION: Predicted conditions reduced A. carbonarius and limited A. ochraceus growth. Antifungals reduced fungal infection (by 40‐84%), although no correlation between climatic conditions and effectiveness of the antifungals was found. However, Switch always showed the greatest reduction and E. arvense (0.02 g mL^?1 extract) the least. Higher temperatures affected OTA production by the isolates in different ways. In general, Switch and Flint Max reduced OTA production, while E. arvense stimulated it. Copyright © 2011 Society of Chemical Industry     

Effects of oilseed substrates (ground nyjer and flax seeds) on the growth and Ochratoxin A production by Aspergillus carbonarius

Aspergillus carbonarius is one of the major Ochratoxin A (OTA) producing fungus. Nyjer and flax seeds are important oilseeds that are used for both human and animal consumption, but they are highly susceptible to fungal growth and mycotoxin contamination. The objectives of this study were to determine the growth and OTA production by A. carbonarius on ground nyjer and flax seeds with water activity levels ranging from 0.82 to 0.98 a_w at three incubation temperatures (20, 30, 37°C). It was found that A. carbonarius was not able to grow on the two types of oilseeds with 0.82 or 0.86 a_w. Also, the fungus was not able to grow on flax seeds with high water activity (0.98 a_w). The OTA was only detected on flax seed samples with 0.94 a_w at 20°C. On nyjer seeds, the highest concentration of OTA (271 μg/kg) was detected from samples with 0.98 a_w incubated at 20°C for 5 days, while on flax seeds the highest OTA (146 μg/kg) was found on the seed samples with 0.94 a_w incubated at 20°C for 15 days. Linear regression models also indicated that 0.98 a_w was optimal for both fungal growth and OTA production on nyjer seeds. Overall, ground nyjer seed is better than flax seed to support growth and OTA production by A. carbonarius.     

Ochratoxin A production by Aspergillus carbonarius on some grape varieties grown in Italy

Fungi responsible for the presence of Ochratoxin A (OTA) in grapes have been identified as belonging to the black aspergilli, Aspergillus section Nigri, among which Aspergillus carbonarius is the main producer. Despite the widespread occurrence of OTA in various types of wine, there is no specific information on the ability of black aspergilli to infect berries and to produce OTA in different grape varieties. The aim of this study was to investigate the susceptibility to A carbonarius of twelve grape varieties representative of a wide range of characteristics, including geographical distribution. In all the conditions of berry status (intact and damaged) and temperature (20 and 25 °C) tested, the incidence of colonised berries and their OTA contents were always low in ‘Bianco d'Alessano’, ‘Pampanuto’ and ‘Uva di Troia’. In contrast, ‘Cabernet Sauvignon’, ‘Trebbiano’ and ‘Verdeca’ showed high fungal incidence and OTA content. The information gathered is relevant for defining risk factors for OTA presence in grapes, even if these data need to be confirmed by observations in vineyards. Copyright © 2004 Society of Chemical Industry     

Impact of non-selective fungicides on the growth and production of ochratoxin A by Aspergillus ochraceus and A. carbonarius in barley-based medium

The aim of this study was to assess the influence of the non-selective fungicides mancozeb, copper oxychloride, and sulfur on the growth and capability for producing ochratoxin A (OTA) of ochratoxigenic isolates of Aspergillus carbonarius and A. ochraceus in barley-based medium. Lag phases and growth rates were determined for each fungicide at different doses, at 15°C and 25°C and at 0.97?a_w . Mancozeb at 40?mg?l^?1 inhibited fungal growth and provided lag phases >24 days at 10–20?mg?l^?1 and 15°C. OTA was observed only at 25°C and doses <10?mg?l^?1. At 15°C, copper oxychloride proved inhibitory at 800?mg?l^?1, while at 25°C growth was not delayed and only high doses decreased OTA levels. Sulfur was inhibitory or provided large lag phases at 5–8?g?l^?1 (at 15°C) while at 25°C growth took place even at 8?g?l^?1, although OTA levels were low or undetectable. The antifungal activity decreased in the order mancozeb?>?copper oxychloride?>?sulfur, and was lower at 25°C than at 15°C. OTA accumulation was affected by the type of fungicide, dose, temperature and time. The efficacy of these fungicides on the growth of A. carbonarius and A. ochraceus and OTA production in barley-based medium is assessed for the first time.     

Capsaicin,an inhibitor of Ochratoxin A production by Aspergillus section Nigri strains in grapes (Vitis vinifera L.)

ABSTRACT

Food decay by spoilage fungi leads to significant economic losses and hazards to consumers’ health due to the potential of mycotoxin occurrence. Ochratoxin A (OTA) is a mycotoxin known as nephrotoxic and carcinogenic to humans. Natural capsaicin was evaluated for its effectiveness against the growth of five Aspergillus section Nigri strains and accumulation of OTA in inoculated black grapes. Results showed that capsaicin was effective in inhibiting fungal growth and OTA production by new four Aspergillus section Nigri strains (ATHUM 6997, 6998, 6999, 7000) and by Aspergillus carbonarius as well. Moreover, capsaicin addition exhibited maximum inhibition of OTA produced by ATHUM 6997, 6998, 6999, and 7000 in black grapes at 28.9%, 8.6%, 68.4%, and 78.1%, respectively. Inhibition percentage of OTA production by A. carbonarius in grapes treated with capsaicin was estimated at 61.5%. These results suggest that capsaicin influences the OTA biosynthesis pathway of all Aspergillus section Nigri strains and therefore could be used as an effective natural preservative against OTA contamination of vineyards. Risk assessment revealed that when grapes are treated with capsaicin, consumers are less exposed to OTA.     

Impact of relative humidity and temperature on visible fungal growth and OTA production of ochratoxigenic Aspergillus ochraceus isolates on grapes

Aspergillus ochraceus is an ochratoxin A (OTA) producer mould found in grapes and this may contribute to OTA contamination in wines and grape juices. The influence of relative humidity (R.H.; 80, 90 and 100%) and temperature (10, 20 and 30 °C) on visible mould growth on grapes and OTA accumulation after 14 days of incubation by this fungal species has been studied using a full factorial design with three replicates.The two abiotic factors and their interaction (R.H.×temperature) affected significantly the A. ochraceus growth in berries, which was maximum at 90–100% R.H. levels. With regard to the optimum temperature level, it occurred at 30 °C at 80 and 90% R.H., whereas no significant differences were detected at 20 and 30 °C when R.H. was 100%.OTA production by A. ochraceus on grapes was not significantly modified by the assayed levels of temperature and R.H, with a mean value of 3.53 ng g⁻¹.Predictive models of percentage of grapes with visible growth of A. ochraceus isolates under different relative humidity and temperature are presented.     

Early detection of Aspergillus carbonarius and A. niger on table grapes: a tool for quality improvement

Aspergillus carbonarius and A. niger aggregate are the main fungal contaminants of table grapes. Besides their ability to cause black rot, they can produce ochratoxin A (OTA), a mycotoxin that has attracted increasing attention worldwide. The objective of this work was to set up a simple and rapid molecular method for the early detection of both fungi in table grapes before fungal development becomes evident. Polymerase chain reaction (PCR)-based assays were developed by designing species-specific primers based on the polyketide synthases (PKS_S) sequences of A. carbonarius and A. niger that have recently been demonstrated to be involved in OTA biosynthesis. Three table grape varieties (Red globe, Crimson seedless, and Italia) were inoculated with A. carbonarius and A. niger aggregate strains producing OTA. The extracted DNA from control (non-inoculated) and inoculated grapes was amplified by PCR using ACPKS2F-ACPKS2R for A. carbonarius and ANPKS5-ANPKS6 for A. niger aggregate. Both primers allowed a clear detection, even in symptomless samples. PCR-based methods are considered to be a good alternative to traditional diagnostic means for the early detection of fungi in complex matrix for their high specificity and sensitivity. The results obtained could be useful for the definition of a ‘quality label’ for tested grapes to improve the safety measures taken to guarantee the production of fresh table grapes.     

Comparative study of toxigenic potential of Aspergillus flavus and Aspergillus niger isolated from Barley as affected by temperature,water activity and carbon source

The objective of the present work was to evaluate the ability of two mycotoxigenic species Aspergillus flavus and Aspergillus niger, isolated from barley, to produce aflatoxin B1 (AFB1) and ochratoxin A (OTA), respectively, as affected by nutritional and environmental factors. Six carbon sources (D-fructose, D-glucose, D-galactose, lactose, sucrose and starch) and different water activities (0.90, 0.95 and 0.98), temperature (20 and 28 °C) and incubation time (5 and 10 days) were tested. The results showed that optimal conditions for growth on Barley Meal Extract Agar (BMEA) medium were 28 °C and 0.95 a_w for A. niger strain and 28 °C and 0.98 a_w for A. flavus strain. Optimal conditions for OTA and AFB1 production were largely different for the two tested strains. A. niger had an optimal OTA production at 0.98 a_w and 20 °C after 10 days of incubation while A. flavus had an optimal AFB1 production at 0.95–0.98 a_w and 28 °C after 5 days of incubation. These results indicates that A. flavus has a higher optimum temperature for mycotoxin synthesis than A. niger and takes greater advantage of drier conditions for maximum AFB1 production. In the current study, both OTA and AFB1 production of A. niger and A. flavus were highly influenced by carbon sources. The sugar that provided the highest toxin levels in the cultures of the two species was sucrose with the lowest levels given by starch. OTA production by A. niger was also highly induced by fructose as carbon sources, while, AFB1 production by A. flavus was favored by glucose. Globally, our results showed, significantly different optimal conditions for production of AFB1 and OTA, respectively, by A. flavus and A. niger.     

Kinetics of Ochratoxin A Production and Accumulation by Aspergillus carbonarius on Synthetic Grape Medium at Different Temperature Levels

ABSTRACT:  The effects of incubation time (up to 10 d) and temperature (7, 15, 20, 25, 30, 35, and 42 °C) on mean ochratoxin A (OTA)-producing capacity and OTA accumulation by 4 Aspergillus carbonarius strains isolated from Spanish and Tunisian grapes were studied on grape-like medium. The limits of growth and OTA production have been identified. OTA production was significantly higher at 20 °C, followed by 25, 15, 30, 35 °C. No growth was observed at 7 °C and 42 °C after 10 d of incubation and, consequently, no OTA was detected at these temperature levels. In general, maximum mean OTA-producing capacity was found earlier with increasing incubation temperatures. However, at 35 °C, OTA was rarely detected although growth was maximum at this temperature. OTA accumulation was maximum after 10 d of incubation for all the temperatures except at 30 °C, were the maximum was detected at earlier incubation time (6 to 8 d) and then remained stable. Colony diameters and OTA accumulation along time were modeled by the Gompertz sigmoidal model and an estimation of maximum OTA accumulation rate and the delay until OTA production could be established. At high temperatures OTA accumulation starts earlier but increases slowly and becomes constant in a few days.     

Effects of different drying treatments on fungal population and ochratoxin A occurrence in sultana type grapes

This study aimed to determine the changes in mould and ochratoxin A (OTA) occurrence in sultanas under three different conventional drying conditions. Five different vineyards were chosen, and the three different treatments were applied to these grapes while drying. At the end of the drying process, total mould and black aspergilli (BA) populations in the samples varied from 2.45 to 5.61 log colony-forming units (CFU) g^–1 and from 0 to 4.92 log CFU g^–1, respectively. Significant increases (p < 0.05) occurred in mould loads depending on the extending drying period. However, independent of vineyard location, all the samples treated with cold dipping solution showed the lowest fungal loads. These results indicate that dipping solution treatment was the most effective drying method to minimise fungal infection of grapes. The expected results could not be achieved by drying grapes artificially contaminated with ochratoxigenic Aspergillus carbonarius spores. Seventy-one of 96 isolates (73.95%) obtained during drying were Aspergillus spp., and the remaining (n = 25, 26.05%) belonged to other genera, such as Penicillium, Trichoderma and Cladosporium. Grape juice-based agar medium was used to determine the realistic OTA production capacities of the isolated mould strains. The highest OTA production capacities were 809.70 ± 9.19, 87.58 ± 16.89 and 45.44 ± 18.78 ng g^–1 in 50% grape juice agar (GJ50), all five of which were from A. niger isolates. OTA was not present in any sample during the drying period; however, OTA was detected in two samples at 0.32 ± 0.15 and 0.52 ± 0.36 µg kg^–1 after the end of the drying process. The limit of detection (LOD) and limit of quantitation (LOQ) of the method used for detecting OTA in samples were 0.1 and 0.3 µg kg^–1, respectively.     

Effect of water activity, temperature and incubation time on growth and ochratoxin A production by Aspergillus niger and Aspergillus carbonarius on maize kernels

The aim of this study was to determine the effects of water activity (a_w) (0.92-0.98), temperature (5-45 °C) and incubation time (5-60 days) on growth and ochratoxin A (OTA) production by Aspergillus niger and Aspergillus carbonarius on maize kernels using a simple method. Colony diameters of both strains at 0.92 a_w were significantly lower than those at 0.96 and 0.98 a_w levels. The optimum growth temperature range for A. niger was 25-40 °C and for A. carbonarius 20-35 °C. A. niger produced OTA from 15 to 40 °C, and the highest OTA level was recorded at 15 °C. The concentration of OTA produced at 0.92 a_w was significantly lower than those at 0.96 and 0.98 a_w. A. carbonarius produced OTA from 15 to 35 °C and the maximum concentration was achieved at 15 °C, although not differing statistically from the concentration detected at 20 °C. At 0.98 a_w the OTA concentration was significantly higher than at 0.96 and 0.92 a_w. Our results show that maize supports both growth and OTA production by A. niger and A. carbonarius. The studied strains were able to produce OTA in maize kernels from the fifth day of incubation over a wide range of temperatures and water availabilities. Although the limit of quantification of our method was higher than that required for the analysis of OTA in food commodities, it has proved to be a useful and rapid way to detect OTA production by fungi inoculated onto natural substrates, in a similar way as for pure culture. Both species could be a source of OTA in this cereal in temperate and tropical zones of the world.     

Characterization of nonochratoxigenic strains of Aspergillus carbonarius from grapes

Aspergillus carbonarius is the main responsible source of ochratoxin A (OTA) in food commodities such as wine, grapes or dried vine fruits from main viticultural regions worldwide. Besides, OTA production is a very consistent property of this species and for this reason atoxigenic isolates of A. carbonarius are very rarely found in natural environments. In the present study, for the first time, three nonochratoxigenic wild strains of A. carbonarius have been discovered, unambiguously identified, characterized in deep and compared to ochratoxigenic strains of the same species. In addition, polyketide synthase (pks) genes suggested to be involved in OTA biosynthesis were also screened in these strains. The identification of the strains was confirmed by ITS-5.8S rRNA, β-tubulin and calmodulin gene sequencing. The three atoxigenic strains did not produce OTA in a conducive culture medium at any of the temperatures and times of incubation tested. Five ketosynthase domains from pks genes previously described in A. carbonarius were detected both in ochratoxigenic and in nonochratoxigenic strains. Atoxigenic strains of A. carbonarius could be useful as biotechnological agents to be used in food industry and as biological agents for control of OTA production in vineyards and other crops.     

Influence of water activity and temperature on conidial germination and mycelial growth of ochratoxigenic isolates of Aspergillus ochraceus on grape juice synthetic medium. Predictive models

The first stages in the development of Aspergillus ochraceus, an ochratoxin A‐producing fungus that infects grapes and may grow on them, have been studied on a synthetic nutrient medium similar to grape in composition. Spore germination and mycelial growth have been tested over a water activity (a_w) and temperature range which could approximate to the real conditions of fungal development on grapes. Optimal germination and growth were observed at 30 °C for all three isolates tested. Maximal germination rates were detected at 0.96–0.99 a_w at 20 °C, while at 10 and 30 °C the germination rates were significantly higher at 0.99 a_w. Although this abiotic factor (a_w) had no significant influence on mycelial growth, growth rates obtained at 0.98 a_w were slight higher than those at other a_w levels. Predictive models for the lag phase before spore germination as a function of water activity and temperature have been obtained by polynomial multiple linear regression, and the resulting response surface models have been plotted. Copyright © 2005 Society of Chemical Industry     

OPTIMIZATION OF NUTRIENTS AND CULTIVATION CONDITIONS IN GLUCOAMYLASE PRODUCTION

Initial adjustment of pH of growth medium in the range of 3.0–5.0 was found to be necessary for optimal production of glucoamylase by a newly isolated strain of Aspergillus niger. Optimum temperature of incubation under stationary conditions was found to be 26–28° C, although incubation at higher temperatures viz. 30 and 37° C led to faster fungal growth rate and increased biomass. In complex medium, the optimum glucose and peptone concentrations were 2 and 3% respectively, and the presence of trace elements was found to be essential for maximal enzyme yield.     

Is intraspecific variability of growth and mycotoxin production dependent on environmental conditions? A study with Aspergillus carbonarius isolates

The aim of this study was to assess the impact of suboptimal environmental conditions on the intraspecific variability of A. carbonarius growth and OTA production using thirty isolates of A. carbonarius.Three a_w/temperature conditions were tested, one optimal (0.98a_w/25 °C) and two suboptimal: 0.90a_w/25 °C and 0.98a_w/37 °C as suboptimal water activity and temperature, respectively, which might take place through over ripening and dehydration of grapes. For each condition, 12 Petri dishes were inoculated, and colony growth and OTA production were measured over time.ANOVA revealed significant differences among μ and λ within the 30 assayed isolates. Coefficients of variation (CV%) revealed a wider dispersion of growth rates at 0.90a_w/25 °C compared to 0.98a_w/25 °C, and a more than 4-fold higher CV at 0.98a_w/37 °C compared to 0.98a_w/25 °C. However, dispersion of lag phases was similar at 0.98a_w/25 °C and 0.90a_w/25 °C and wider at 0.98a_w/37 °C.There were significant differences (p < 0.05) among OTA levels (ng/mm²) for the different conditions, values being lower under marginal conditions, and particularly at 0.98a_w/37 °C. Coefficients of variation (CV%) revealed a wider dispersion of OTA production at 0.90a_w/25 °C compared to 0.98a_w/25 °C, while CV at 0.98a_w/37 °C was similar to that at 0.98a_w/25 °C.In order to address the strain variability in growth initiation and prove the well-established notion of reducing OTA in foods by preventing fungal growth, a greater number of strains should be included when developing models for conditions that are suboptimal both for a_w for OTA production and temperature levels for growth.     

Bacterial Histamine Production as a Function of Temperature and Time of Incubation

Optimal temperature, lower temperature limit, extent, and rate of histamine production in a tuna fish infusion broth (TFIB) varied for the strains of Proteus morganii, Klebsiella pneumoniae, Hafnia alvei, Citrobacter freundii, and Escherichia coli studied. P. morganii and K. pneumoniae produced large quantities of histamine in a relatively short incubation period (<24 hr) at 15°C, 30°C, and 37°C; production was fastest at 37°C. H. alvei, C. freundii, and E. coli produced toxicologically significant levels of histamine (>2500 nmoles/ml) only at 30°C and 37°C on prolonged incubation (≥48 hr). At 72 hr of incubation, optimal temperature for histamine production was 37°C for E. coli and C freundii; 30°C for P. morganii strain 110SC2, K. pneumoniae, and H. alvei; and 15°C for P. morganii strain JM. The lower temperature limits for production of toxicologically significant levels of histamine in TFIB were 7°C for K. pneumoniae; 15°C for both P. morganii strains; and 30°C for H. alvei, C. freundii, and E. coli.     

Occurrence of ochratoxin A and toxigenic potential of fungal isolates from Spanish grapes

This paper reports the results from an extensive survey of filamentous fungi isolated from wine‐producing grapes and their capacity to produce ochratoxin A (OTA) on Czapek Yeast Autolysate agar (CYA), in order to assess their potential for producing this toxin in grapes. Grapes were sampled from four Spanish wine‐producing regions during 2001. The fungal infection in berries increased with time, reaching 100% at harvest. A total of 386 isolates of Aspergillus section Nigri and 10 of Aspergillus section Circumdati were isolated and tested for their ability to produce OTA in CYA. 21 strains produced OTA (18 Aspergillus section Nigri and 3 Aspergillus section Circumdati). Aspergillus section Circumdati isolates produced higher amounts of OTA than Aspergillus section Nigri ones, with means of 10.76 µg g^?1 CYA and 1.42 µg g^?1 CYA, respectively. Despite this, black aspergilli are believed to be highly responsible for the OTA levels found in musts and wines, as it is more widespread in grapes. Musts (n = 40) produced from the grapes collected were analysed. 15% were found to contain OTA, concentrations ranging from 0.091 to 0.813 ng ml^?1 (detection limit: 0.07 ng ml^?1), but no correlation was found with the ochratoxigenic moulds isolated from grapes. Copyright © 2004 Society of Chemical Industry     

Inhibition of A. carbonarius growth and reduction of ochratoxin A by bacteria and yeast composites of technological importance in culture media and beverages

Five composites of yeast and six of bacterial isolates from fermented products were studied, in order to assess their ability to inhibit Aspergillus carbonarius growth and reduce OTA concentration in culture media and beverages. The antagonistic effect of the above composites against A. carbonarius growth was studied in synthetic grape medium of pH 3.5 and a_w 0.98, 0.95, 0.92 after incubation at 25 °C. Different combinations of initial inocula of bacteria or yeast composites and fungi were used (10² cfu/mL vs 10⁵ spores/mL; 10⁵ cfu/mL vs 10² spores/mL; and 10⁵ cfu/mL vs 10⁵ spores/mL). Regarding the OTA reduction experiment, 10³ and 10⁷ cfu/mL of the bacteria and yeast composites were inoculated in liquid media of different pH (3.0, 4.0, 5.0, and 6.1 or 6.5) and initial OTA concentration (50 and 100 μg/L) and incubated at 30 °C. Moreover, grape juice, red wine, and beer were supplemented with 100 μg/L of OTA and inoculated with composites of 16 yeasts (16YM) and 29 bacterial (29BM) strains (10⁷ cfu/mL) to estimate the kinetics of OTA reduction at 25 °C for 5 days. Fungal inhibition and OTA reduction were calculated in comparison to control samples. None of the bacterial composites inhibited A. carbonarius growth. The high inoculum of yeast composites (10⁵ cfu/mL) showed more efficient fungal inhibition compared to cell density of 10² cfu/mL. All yeast composites showed higher OTA reduction (up to 65%) compared to bacteria (2-25%), at all studied assays. The maximum OTA reduction was obtained at pH 3.0 by almost all yeast composites. For all studied beverages the decrease in OTA concentration was higher by yeasts (16YM) compared to bacteria (29BM). The highest OTA reduction was observed in grape juice (ca 32%) followed by wine (ca 22%), and beer (ca 12%). The present findings may assist in the control of A. carbonarius growth and OTA production in fermented foodstuffs by the use of proper strains of technological importance.     

Phylogenetic characterization and ochratoxin A--fumonisin profile of black Aspergillus isolated from grapes in Argentina

Aspergillus section Nigri populations isolated from seven growing regions from Argentina were characterized by sequencing in order to identify species responsible for production of ochratoxin A (OTA) and fumonisins (FB_s). Sequences of genes encoding calmodulin, β-tubulin, the second largest subunit of RNA polymerase II and translation elongation factor 1 alpha were analysed. The phylogenetic analysis showed the presence of six lineages: A. carbonarius, A. tubingensis, A. niger, A. japonicus, A. homomorphus and A. foetidus grouped in four major clusters. The molecular tools used allowed the identification for the first time of A. homomorphus from vineyards. OTA production confirmed the importance of A. carbonarius as the main ochratoxigenic species isolated and, to a variable degree, of A. niger and A. tubingensis, which were by far the most commonly occurring species on grapes in Argentina. The only strains able to produce OTA and fumonisins (B₂-B₄) belong to the A. niger cluster.     

Biodiversity of Aspergillus section Nigri populations in Argentinian vineyards and ochratoxin A contamination

Aspergillus section Nigri are described as the main source of ochratoxin A (OTA) contamination in grapes and wine worldwide. The knowledge of the factors affecting grape contamination by species included in this section and OTA production is essential to be able to reduce their presence, not only to improve wine quality, but also to maintain their safety. Therefore, the aims of this study were to determine the incidence of Aspergillus section Nigri species harvested in different grape-growing regions from Argentina, their ability to produce OTA, to correlate with meteorological conditions and geographical coordinates with their prevalence and to evaluate the OTA natural occurrence in grapes and wines. The morphological identification showed that Aspergillus niger aggregate species were the most prevalent ones, followed by Aspergillus carbonarius and Aspergillus uniseriate. These populations were confirmed through using AFLP markers and sequencing and, Aspergillus tubingensis was separated from A. niger aggregate. Climatic factors, altitude, longitude and latitude have influenced on the distribution of species included in the section. A. carbonarius and A. niger were OTA producers but differed in their OTA producing ability. Temperature was the factor which influenced the most over the highest incidence of A. carbonarius in La Rioja and San Juan regions. The trellis system in vineyards and drip irrigation also influenced the species isolation. The OTA levels detected in grapes and wines were low, but grape variety was more important in susceptibility to fungal infection and OTA levels.