Mycotoxin production by Alternaria strains isolated from Argentinean wheat

Review: Strategies and technologies in preventing regulated and emerging mycotoxin co-contamination in forage for safeguarding ruminant health

Ruminants are often considered less susceptible to mycotoxins than monogastrics, owing to rumen microflora converting mycotoxins to less toxic compounds or several compounds present in the rumen-reticulum compartment, being able to bind the mycotoxin "mother" molecule that make them unavailable for absorption process in the gastro-intestinal tract of host animals. However, if ruminants consume feed contaminated by mycotoxins for long periods, their growth, development, and fertility can be compromised. Among regulated mycotoxins, the most studied and known for their effects are aflatoxins (AFs) AFB1, AFB2, AFG1 and AFG2, as well as the AFM1 for its high importance in dairy sector, deoxynivalenol (DON) and its metabolites 3/15 acetyl-DON and 3-glucoside DON, T-2 and HT-2 toxins, zearalenone, fumonisins, in particular that belong to the B class, and ochratoxin A. Furthermore, because of the emergence of multiple emerging mycotoxins that are detectable in feed utilised in ruminant diets, such as ensiled forage, there is now a growing focus on investigating these compounds by the scientific community to deepen their toxicity for animal health. Despite the enhancement of research, it is remarkable that there is a paucity of in vivo trials, as well as limited studies on nutrient digestibility and the impact of these molecules on rumen and intestinal functions or milk yield and quality. In this review, recent findings regarding the occurrence of regulated and emerging mycotoxins in forage and their possible adverse effects on dairy cattle are described, with special emphasis on animal performance and on rumen functionality.

Characterization and toxicological potential of Alternaria alternata associated with post-harvest fruit rot of Prunus avium in China

Post-harvest fruit rot caused by Alternaria species is one of the most important threats to the fruit industry. Post-harvest rot on sweet cherry (Prunus avium) fruit was observed in the fruit markets of the Haidian district of Beijing, China. The fungal isolates obtained from the infected sweet cherry fruits matched the descriptions of Alternaria alternata based on the morphology and multi-gene (ITS, endo-PG, and Alta1) sequence analysis. Pathogenicity tests indicated that ACT-3 was the most virulent isolate, exhibiting typical post-harvest fruit rot symptoms. Physiological studies revealed that the optimal conditions for the growth of ACT-3 were temperature of 28°C, water activity of 0.999, and pH of 8 with 87, 85, and 86 mm radial growth of ACT-3 on a potato dextrose agar (PDA) medium, respectively, at 12 days post-inoculation (dpi). Moreover, the fungus showed the highest growth on a Martin agar medium (MAM) modified (85 mm) and a PDA medium (84 mm) at 12 dpi. The proliferation of the fungus was visualized inside the fruit tissues by confocal and scanning electron microscope (SEM), revealing the invasion and destruction of fruit tissues. Alternaria mycotoxins, tenuazonic acid (TeA), and alternariol (AOH) were detected in five representative isolates by HPLC analysis. The highest concentrations of TeA (313 μg/mL) and AOH (8.9 μg/mL) were observed in ACT-6 and ACT-3 isolates, respectively. This study is the first to present a detailed report on the characteristics and proliferation of A. alternata associated with sweet cherry fruit rot and the detection of toxic metabolites.

Different diagnostic approaches for the characterization of the fungal community and Fusarium species complex composition of Italian durum wheat grain and correlation with secondary metabolite accumulation

BACKGROUND

The evolution of the fungal communities associated with durum wheat was assessed using different diagnostic approaches. Durum wheat grain samples were collected in three different Italian cultivation macro-areas (north, center and south). Fungal isolation was realized by potato dextrose agar (PDA) and by deep-freezing blotter (DFB). Identification of Fusarium isolates obtained from PDA was achieved by partial tef1α sequencing (PDA + tef1α), while those obtained from DFB were identified from their morphological characteristics (DFB + mc). The fungal biomass of eight Fusarium species was quantified in grains by quantitative polymerase chain reaction (qPCR). Fungal secondary metabolites were analyzed in grains by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Correlations between Fusarium detection techniques (PDA + tef1α; DFB + mc and qPCR) and mycotoxins in grains were assessed.

RESULTS

Alternaria and Fusarium showed the highest incidence among the fungal genera developed from grains. Within the Fusarium community, PDA + tef1α highlighted that F. avenaceum and F. graminearum were the most represented members, while, DFB + mc detected a high presence of F. proliferatum. Alternaria and Fusarium mycotoxins, principally enniatins, were particularly present in the grain harvested in central Italy. Deoxynivalenol was mainly detected in northern-central Italy.

CONCLUSIONS

The adoption of the different diagnostic techniques of Fusarium detection highlighted that, for some species, qPCR was the best method of predicting their mycotoxin contamination in grains. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Interacting Abiotic Factors Affect Growth and Mycotoxin Production Profiles of Alternaria Section Alternaria Strains on Chickpea-Based Media

Chickpea is susceptible to fungal infection and mycotoxin contamination. Argentina exports most of its chickpea production; thus, its quality is of concern. The Alternaria fungal genus was found to be prevalent in chickpea samples from Argentina. The species within this genus are able to produce mycotoxins, such as alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TA). In this context, we evaluated the effect of water activity (0.99, 0.98, 0.96, 0.95, 0.94, 0.92, and 0.90 a_W), temperature (4, 15, 25, and 30 °C), incubation time (7, 14, 21, and 28 days), and their interactions on mycelial growth and AOH, AME, and TA production on chickpea-based medium by two A. alternata strains and one A. arborescens strain isolated from chickpea in Argentina. Maximum growth rates were obtained at the highest a_W (0.99) and 25 °C, with growth decreasing as the a_W of the medium and the temperature were reduced. A. arborescens grew significantly faster than A. alternata. Mycotoxin production was affected by both variables (a_W and temperature), and the pattern obtained was dependent on the strains/species evaluated. In general, both A. alternata strains produced maximum amounts of AOH and AME at 30 °C and 0.99-0.98 a_W, while for TA production, both strains behaved completely differently (maximum levels at 25 °C and 0.96 a_W for one strain and 30 °C and 0.98 a_W for the other). A. arborescens produced maximum amounts of the three toxins at 25 °C and 0.98 a_W. Temperature and a_W conditions for mycotoxin production were slightly narrower than those for growth. Temperature and a_W conditions assayed are those found during chickpea grain development in the field, and also could be present during storage. This study provides useful data on the conditions representing a risk for contamination of chickpea by Alternaria toxins.

The Potential of Alternaria Toxins Production by A. alternata in Processing Tomatoes

As a filamentous and spoilage fungus, Alternaria spp. can not only infect processing tomatoes, but also produce a variety of mycotoxins which harm the health of human beings. To explore the production of Alternaria toxins in processing tomatoes during growth and storage, four main Alternaria toxins and four conjugated toxins were detected by ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and ultra-performance liquid chromatography-ion mobility quadrupole time-of-flight mass spectrometry (UPLC-IMS QToF MS) in processing tomatoes on different days after being inoculated with A. alternata. The results show that the content of Alternaria toxins in an in vivo assay is higher than that under field conditions. Tenuazonic acid (TeA) is the predominant toxin detected in the field (205.86~41,389.19 μg/kg) and in vivo (7.64~526,986.37 μg/kg) experiments, and the second-most abundant toxin is alternariol (AOH). In addition, a small quantity of conjugated toxins, AOH-9-glucoside (AOH-9-Glc) and alternariol monomethyl ether-3-glucoside (AME-3-Glc), were screened in the in vivo experiment. This is the first time the potential of Alternaria toxins produced in tomatoes during the harvest period has been studied in order to provide data for the prevention and control of Alternaria toxins.

Key Global Actions for Mycotoxin Management in Wheat and Other Small Grains

Mycotoxins in small grains are a significant and long-standing problem. These contaminants may be produced by members of several fungal genera, including Alternaria, Aspergillus, Fusarium, Claviceps, and Penicillium. Interventions that limit contamination can be made both pre-harvest and post-harvest. Many problems and strategies to control them and the toxins they produce are similar regardless of the location at which they are employed, while others are more common in some areas than in others. Increased knowledge of host-plant resistance, better agronomic methods, improved fungicide management, and better storage strategies all have application on a global basis. We summarize the major pre- and post-harvest control strategies currently in use. In the area of pre-harvest, these include resistant host lines, fungicides and their application guided by epidemiological models, and multiple cultural practices. In the area of post-harvest, drying, storage, cleaning and sorting, and some end-product processes were the most important at the global level. We also employed the Nominal Group discussion technique to identify and prioritize potential steps forward and to reduce problems associated with human and animal consumption of these grains. Identifying existing and potentially novel mechanisms to effectively manage mycotoxin problems in these grains is essential to ensure the safety of humans and domesticated animals that consume these grains.

Alternaria Mycotoxins: An Overview of Toxicity, Metabolism, and Analysis in Food

The genus Alternaria is widely distributed in the environment. Numerous species of the genus Alternaria can produce a variety of toxic secondary metabolites, called Alternaria mycotoxins. In this review, natural occurrence, toxicity, metabolism, and analytical methods are introduced. The contamination of these toxins in foodstuffs is ubiquitous, and most of these metabolites present genotoxic and cytotoxic effects. Moreover, Alternaria toxins are mainly hydroxylated to catechol metabolites and combined with sulfate and glucuronic acid in in vitro arrays. A more detailed summary of the metabolism of Alternaria toxins is presented in this work. To effectively detect and determine the mycotoxins in food, analytical methods with high sensitivity and good accuracy are also reviewed. This review will guide the formulation of maximum residue limit standards in the future, covering both toxicity and metabolic mechanism of Alternaria toxins.

Data-dependent acquisition based high-resolution mass spectrum for trace Alternaria mycotoxin analysis and sulfated metabolites identification

Alternaria mycotoxins are food-related compounds that are mainly produced by Alternaria fungi species. However, it's difficult for Alternaria mycotoxins analysis, especially for conjugated metabolites in food safety surveillance. In this work, a novel data-dependent acquisition (DDA) full mass scan and products scan protocol was proposed for qualitative and quantitative analysis of five target mycotoxins in tomato samples using ultra-high-performance liquid chromatography coupled with quadrupole Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap). In total, 24 sulfated metabolites were detected with post-data analysis techniques, and two sulfated metabolites (AME-sulfated and AOH-sulfated) were identified in Alternaria fungi -inoculated tomatoes. In addition, a custom database was established, and it was successfully applied for Alternaria mycotoxins and sulfated metabolites screening in tomatoes. With the improvement in high-resolution mass spectrometry (HRMS) as well as post-data analysis techniques, DDA based HRMS method could be widely applied for compound analysis, identification, and screening in quantitative field.

The Sorghum Grain Mold Disease Complex: Pathogens, Host Responses, and the Bioactive Metabolites at Play

Grain mold is a major concern in sorghum [Sorghum bicolor (L.) Moench] production systems, threatening grain quality, safety, and nutritional value as both human food and livestock feed. The crop's nutritional value, environmental resilience, and economic promise poise sorghum for increased acreage, especially in light of the growing pressures of climate change on global food systems. In order to fully take advantage of this potential, sorghum improvement efforts and production systems must be proactive in managing the sorghum grain mold disease complex, which not only jeopardizes agricultural productivity and profitability, but is also the culprit of harmful mycotoxins that warrant substantial public health concern. The robust scholarly literature from the 1980s to the early 2000s yielded valuable insights and key comprehensive reviews of the grain mold disease complex. Nevertheless, there remains a substantial gap in understanding the complex multi-organismal dynamics that underpin the plant-pathogen interactions involved - a gap that must be filled in order to deliver improved germplasm that is not only capable of withstanding the pressures of climate change, but also wields robust resistance to disease and mycotoxin accumulation. The present review seeks to provide an updated perspective of the sorghum grain mold disease complex, bolstered by recent advances in the understanding of the genetic and the biochemical interactions among the fungal pathogens, their corresponding mycotoxins, and the sorghum host. Critical components of the sorghum grain mold disease complex are summarized in narrative format to consolidate a collection of important concepts: (1) the current state of sorghum grain mold in research and production systems; (2) overview of the individual pathogens that contribute to the grain mold complex; (3) the mycotoxin-producing potential of these pathogens on sorghum and other substrates; and (4) a systems biology approach to the understanding of host responses.

Natural occurrence of Alternaria mycotoxins in wheat and potential of reducing associated risks using magnolol

BACKGROUND

Wheat is one of three major food crops in China. Alternaria species can cause spoilage of wheat with consequent mycotoxin accumulation. Alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TeA) are the most common and frequently studied mycotoxins. There are limited regulations placed on Alternaria mycotoxin concentrations worldwide due to the lack of toxicity data available. More data on the levels of mycotoxin contamination are also needed. It is also important to reduce the risks of Alternaria mycotoxins.

RESULTS

One hundred and thirty-two wheat samples were collected from Hebei Province, China, and analyzed for AOH, AME, and TeA. Tenuazonic acid was found to be the predominant Alternaria mycotoxin, especially in flour samples. Studying Alternaria species that cause black-point disease of wheat indicated that Alternaria alternata and Alternaria tenuissima were the dominant species. Most of the Alternaria strains studied produced more than one mycotoxin and TeA was produced at the highest concentration, which may have resulted in the high level of TeA contamination in the wheat samples. Furthermore, magnolol displayed obvious antifungal and antimycotoxigenic activity against Alternaria. This is the first report on the antimycotoxigenic activity of magnolol against Alternaria species.

CONCLUSION

The Alternaria mycotoxin contamination levels in wheat and wheat products from Hebei Province, China, were correlated with the toxigenic capacity of the Alternaria strains colonizing the wheat. Considering its safety, magnolol could be developed as a natural fungicide in wheat, or as a natural alternative food preservative based on its strong antifungal and antimycotoxigenic activity against Alternaria strains. © 2020 Society of Chemical Industry.

Mycotoxins Biocontrol Methods for Healthier Crops and Stored Products

Contamination of crops with phytopathogenic genera such as Fusarium, Aspergillus, Alternaria, and Penicillium usually results in mycotoxins in the stored crops or the final products (bread, beer, etc.). To reduce the damage and suppress the fungal growth, it is common to add antifungal substances during growth in the field or storage. Many of these antifungal substances are also harmful to human health and the reduction of their concentration would be of immense importance to food safety. Many eminent researchers are seeking a way to reduce the use of synthetic antifungal compounds and to implement more eco-friendly and healthier bioweapons against fungal proliferation and mycotoxin synthesis. This paper aims to address the recent advances in the effectiveness of biological antifungal compounds application against the aforementioned fungal genera and their species to enhance the protection of ecological and environmental systems involved in crop growing (water, soil, air) and to reduce fungicide contamination of food derived from these commodities.

Occurrence of Alternaria and Other Toxins in Cereal Grains Intended for Animal Feeding Collected in Slovenia: A Three-Year Study

In recent years, the less-studied Alternaria mycotoxins have attracted increasing interest due to the lack of survey data and their ability to cause toxic effects in animals and humans. To fill the gap, the aim of this three-year survey was to investigate the presence and co-occurrence of Alternaria and other mycotoxins in a total of 433 cereal grain samples from Slovenian farms and agricultural cooperatives from 2014 to 2016. Using the multi-mycotoxin method, 14 mycotoxins were determined. In 53% of 433 analysed samples, contamination with at least one mycotoxin was found. Deoxynivalenol (DON) and tenuazonic acid (TeA) were present in 32% and 26% of cereal grain samples, respectively, whereas alternariol (AOH), tentoxin (TEN), alternariol monomethyl ether (AME), 3- and 15-acetyldeoxynivalenol (3- and 15-AcDON), and zearalenone (ZEN) were present in fewer than 15% of the samples. Ochratoxin A (OTA) was found in one rye sample, while diacetoxyscirpenol (DAS), HT-2 and T-2 toxin, and fumonisins B1 and B2 (FB1 and FB2) were not detected. The highest maximum and median concentrations of Alternaria toxins were determined in spelt in 2016 (TeA, 2277 µg/kg and 203 µg/kg, respectively), and those of Fusarium toxins in wheat in 2015 (DON, 4082 µg/kg and 387 µg/kg, respectively). The co-occurrence of two or more mycotoxins was found in 43% of the positive samples. The correlations between Alternaria toxins were very weak but statistically significant (r: 0.15-0.17, p: 0.0042-0.0165). A well-known correlation between Fusarium toxins DON and ZEN was weak and highly significant (r = 0.28, p < 0.0001).

Chemotaxonomic Profiling of Canadian Alternaria Populations Using High-Resolution Mass Spectrometry

Alternaria spp. occur as plant pathogens worldwide under field and storage conditions. They lead to food spoilage and also produce several classes of secondary metabolites that contaminate the food production chain. From a food safety perspective, the major challenge of assessing the risk of Alternaria contamination is the lack of a clear consensus on their species-level taxonomy. Furthermore, there are currently no reliable DNA sequencing methods to allow for differentiation of the toxigenic potential of these fungi. Our objective was to determine which species of Alternaria exist in Canada, and to describe the compounds they make. To address these issues, we performed metabolomic profiling using liquid chromatography high-resolution mass spectrometry (LC-HRMS) on 128 Canadian strains of Alternaria to determine their chemotaxonomy. The Alternaria strains were analyzed using principal component analysis (PCA) and unbiased k-means clustering to identify metabolites with significant differences (p < 0.001) between groups. Four populations or 'chemotypes' were identified within the strains studied, and several known secondary metabolites of Alternaria were identified as distinguishing metabolites, including tenuazonic acid, phomapyrones, and altenuene. Though species-level identifications could not be concluded for all groups through metabolomics alone, A. infectoria was able to be identified as a distinct population.

Molecular Identification and Mycotoxin Production by Alternaria Species Occurring on Durum Wheat, Showing Black Point Symptoms

Black point is a fungal disease of wheat, mainly associated with mycotoxigenic Alternaria species. Affected wheat kernels are characterized by dark brown discolouration of the embryo region and reduction of grain quality. Potential risk is the possible accumulation of Alternaria mycotoxins, alternariol (AOH), alternariol-monomethyl ether (AME), tenuazonic acid (TA), and altenuene (ALT), provided by haemato-toxic, genotoxic, and mutagenic activities. One hundred and twenty durum wheat samples belonging to 30 different genotypes grown in Bologna and Modena areas, in Italy, showing black point symptoms, were analyzed for Alternaria species and their mycotoxin contamination. Alternariol was selected as an indicator of the capability of the Alternaria species to produce mycotoxin in vivo in field conditions. The data showed that Alternaria species occurred in 118 out of 120 wheat kernels samples, with the incidence of infected kernels ranging between 1% and 26%. Moreover, AOH was detected by using a HPLC with a diode array detector (LC-DAD) in 98 out of 120 samples with values ranging between 24 and 262 µg Kg⁻¹. Ninety-two Alternaria representative strains, previously identified morphologically, were identified at species/section level using gene sequencing, and therefore were analyzed for their mycotoxin profiles. Eighty-four strains, phylogenetically grouped in the Alternaria section, produced AOH, AME, and TA with values up to 8064, 14,341, and 3683 µg g⁻¹, respectively, analyzed by using a LC-DAD. On the other hand, eight Alternaria strains, included in Infectoriae Section, showed a very low or no capability to produce mycotoxins.

Natural occurrence of Alternaria mycotoxins in malting barley grains in the main producing region of Argentina

BACKGROUND

Barley (Hordeum vulgare L.) is one of the most important cereals worldwide, and its quality is affected by fungal contamination such as species of the genus Alternaria. No information is available about the occurrence of Alternaria mycotoxins in Argentinean barley grains, which is of concern, because they can be transferred into malt and beer. The aim of this study was to analyze the occurrence of alternariol (AOH), alternariol monomethyl ether (AME) and tenuazonic acid (TeA) in malting barley grains from the main producing region of Argentina during the 2014 and 2015 growing seasons.

RESULTS

The most frequent mycotoxin was AOH (64%), which was detected at higher levels (712 μg kg^-1 ) compared with other studies, followed by TeA (37%, 1522 μg kg^-1 ), while AME was present in five samples in the 2015 growing season only, with a mean of 4876 μg kg^-1 . A similar frequency of mycotoxin occurrence was observed in both years (80.8 vs 85.3%), but more diverse contamination was found in 2015, which was characterized by lower accumulated precipitation. Nevertheless, AOH was more frequently found in 2014 than in 2015 (80.8 and 47.1% respectively). A negative correlation between AOH concentration and temperature was observed. The susceptibility of different barley varieties to mycotoxin accumulation varied with the mycotoxin, geographical location and meteorological conditions.

CONCLUSION

The results obtained in the present work represent a tool for risk assessment of exposition to these mycotoxins and could be used by food safety authorities to determine the need for their regulation. Furthermore, the establishment of a hazard analysis and critical control point (HACCP) system to minimize fungal and mycotoxin contamination in barley from farm to processing could be apply to ensure food safety. © 2019 Society of Chemical Industry.

Benzyl isothiocyanate fumigation inhibits growth, membrane integrity and mycotoxin production inAlternaria alternata

The antifungal activity of benzyl isothiocyanate (BITC) against pear pathotype-Alternaria alternata, the causal agent of pear black spot, and its possible mechanisms were studied. The results indicated that both the spore germination and mycelial growth of A. alternata were significantly inhibited by BITC in a dose-dependent manner. BITC concentrations at 1.25 mM completely suppressed mycelial growth of A. alternata and prevented ≥50% of black spot development in wounded pears inoculated with A. alternata. Microscopic analyses and propidium iodide (PI) staining showed that spore morphology in A. alternata treated with BITC at 0.625 mM was severely damaged. Relative electrical conductivity and lysis ability assays further showed that BITC treatment destroyed the integrity of the plasma membrane. Additionally, mycotoxin production was inhibited by 0.312 mM BITC, and the inhibitory rates of alternariol monomethyl ether (AME), alternariol (AOH), altenuene (ALT) and tentoxin (TEN) were 89.36%, 84.57%, 91.41% and 67.78%, respectively. The above results suggest that BITC exerts antifungal activity through membrane-targeted mechanisms.

The antifungal activity of benzyl isothiocyanate (BITC) against pear pathotype-Alternaria alternata, the causal agent of pear black spot, and its possible mechanisms were studied.

Variation of Fungal Metabolites in Sorghum Malts Used to Prepare Namibian Traditional Fermented Beverages Omalodu and Otombo

Sorghum malts, which are important ingredients in traditional fermented beverages, are commonly infected by mycotoxigenic fungi and mycotoxins may transfer into the beverages, risking consumers’ health. Liquid chromatography–tandem mass spectrometry was used to determine variation of fungal metabolites in 81 sorghum malts processed for brewing of Namibian beverages, otombo (n = 45) and omalodu (n = 36). Co-occurrence of European Union (EU)-regulated mycotoxins, such as patulin, aflatoxins (B₁, B₂, and G₂), and fumonisins (B₁, B₂, and B₃) was detected in both malts with a prevalence range of 2–84%. Aflatoxin B₁ was quantified in omalodu (44%) and otombo malts (14%), with 20% of omalodu malts and 40% of otombo malts having levels above the EU allowable limit. Fumonisin B₁ was quantified in both omalodu (84%) and otombo (42%) malts. Emerging mycotoxins, aflatoxin precursors, and ergot alkaloids were quantified in both malts. Notably, 102 metabolites were quantified in both malts, with 96% in omalodu malts and 93% in otombo malts. An average of 48 metabolites were quantified in otombo malts while an average of 67 metabolites were quantified in omalodu malts. The study accentuates the need to monitor mycotoxins in sorghum malts intended for brewing and to determine their fate in the beverages.

Effect of Wheat Milling Process on the Distribution of Alternaria Toxins

Alternaria toxins are mycotoxins produced by various Alternaria species which, besides the Fusarium species, represent the principal contaminants of wheat worldwide. As currently, only limited information on the behaviour of Alternaria toxins during processing of cereals is available, the objective of this study was to investigate the effect of the dry milling process of wheat on Alternaria toxins distribution. Alternariol (AOH), alternariol monomethyl ether (AME) and tenuazonic acid (TeA) content were analysed by high performance liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) in all milling fractions of untreated (control), fungicide-treated, Alternaria tenuissima inoculated and commercial wheat sample. After dry milling process, in last break and milling flows and by-products, increased concentration of examined Alternaria toxins was detected. TeA was quantified in almost all milling fractions in all tested wheat samples, while AOH and AME were detectable mostly in last break and milling flows and by-products. In respect to the contamination with Alternaria toxins, white flour can be considered as relatively safe product. Since Alternaria toxins are concentrated mainly in the peripheral parts of the kernel, a special attention should be given to their content in low-grade flours and milling by-products.

Alternaria mycotoxins in grains from Albania: alternariol, alternariol monomethyl ether, tenuazonic acid and tentoxin

The presence of four Alternaria toxins in maize and wheat harvested in 2014 and 2015 in Albania was investigated. In total, 45 samples of maize and 71 samples of wheat were collected from the country’s main producing regions. The presence of alternariol (AOH), alternariol monomethyl ether (AME), tenuazonic acid (TeA) and tentoxin (TTX) was studied by an LC-MS/MS method. The incidence of Alternaria toxins in maize was 45.2% in the year 2014 and 7.1% in 2015, and the contamination rate in wheat was 82.9% in 2014 and 86.1% in 2015. Considering maize and wheat samples together, 65.2 and 64.0% of samples were contaminated by Alternaria toxins in the harvesting years 2014 and 2015, respectively. The occurrence rate was much higher in wheat than in maize, but the concentrations were higher in maize. The highest concentration of total Alternaria toxins in maize was 1,283 μg/kg (mean 243.0 μg/kg, median 110.2 μg/kg), while the maximum concentration in wheat was 175.7 μg/kg (mean 29.9 μg/kg, median 16.5 μg/kg). TeA was the major Alternaria mycotoxin detected. It was found in 70 out of 116 samples (60.3%). Chronic exposure of the adult population in Albania to Alternaria toxins through cereal consumption was assessed by the estimated daily intake (EDI) taking into account daily consumption of wheat and maize of 380 and 4.9 g, respectively. The main contribution to chronic dietary exposure was by TeA originating from wheat, with EDIs of 88.6-94.1 ng/kg body weight (bw) per day in 2014 and 152.7-155.5 ng/kg bw per day in 2015. TTX EDIs were 7.8- 34.0 and 10.6-38.7 ng/kg bw per day in 2014 and 2015, respectively. The contribution of AOH and AME originating from wheat was 0-31.7 ng/kg bw per day. The contribution of Alternaria toxins through maize consumption was significantly lower.

Alternaria species associated to wheat black point identified through a multilocus sequence approach

Black point is one of the most important wheat disease and its incidence is increasing worldwide due to climate change too. Among the fungal genera that can cause black point, Alternaria is one of the predominant genus, often associated with mycotoxin contamination. The correct identification is the baseline for prevention and control of the disease. Taxonomy of the genus Alternaria is not completely clear yet, since its species can be differentiated for few morphological traits and, in some cases, also molecular phylogeny is not very effective in establishing species boundaries. In this study, one-hundred sixty-four strains, isolated from wheat kernels affected by black point sampled worldwide, were analyzed in order to assess their identity. Sequences of elongation factor, β-tubulin, glyceraldehyde-3-phosphate dehydrogenase and allergen alt-a1 genes were used to identify the variability of this population and their phylogenetic relationships. Isolates were grouped in two main clades: the Alternaria section, including A. alternata, A. tenuissima and A. arborescens species, and the Infectoriae section, that includes the two species A. infectoria and A. triticina. Comparison of isolates according with their area of isolation did not show a correlation between phylogeny and geographic origin. Indeed, the isolates grouped on the base of only their phylogenetic relationship. Due to the data arisen by our study, we strongly recommend a multilocus sequence approach to define Alternaria species, based on common genes and procedures to be unanimously shared by scientific community dealing with Alternaria genus. Moreover, we suggest that A. alternata, A. tenuissima, A. turkisafria and A. limoniasperae species would be merged in the defined species A. alternata. Finally we recommend to consider a taxonomic re-evaluation of the Infectoriae section that, for the morphology, sexuality, genetic and mycotoxin profile of the species included, could be defined as different fungal genus from Alternaria.

Phylogeny and Mycotoxin Characterization of Alternaria Species Isolated from Wheat Grown in Tuscany, Italy

Wheat, the main source of carbohydrates worldwide, can be attacked by a wide number of phytopathogenic fungi, included Alternaria species. Alternaria species commonly occur on wheat worldwide and produce several mycotoxins such as tenuazonic acid (TA), alternariol (AOH), alternariol-monomethyl ether (AME), and altenuene (ALT), provided of haemato-toxic, genotoxic, and mutagenic activities. The contamination by Alternaria species of wheat kernels, collected in Tuscany, Italy, from 2013 to 2016, was evaluated. Alternaria contamination was detected in 93 out of 100 field samples, with values ranging between 1 and 73% (mean of 18%). Selected strains were genetically characterized by multi-locus gene sequencing approach through combined sequences of allergen alt1a, glyceraldeyde-3-phosphate dehydrogenase, and translation elongation factor 1α genes. Two well defined groups were generated; namely sections Alternaria and Infectoriae. Representative strains were analyzed for mycotoxin production. A different mycotoxin profile between the sections was shown. Of the 54 strains analyzed for mycotoxins, all strains included in Section Alternaria produced AOH and AME, 40 strains (99%) produced TA, and 26 strains (63%) produced ALT. On the other hand, only a very low capability to produce both AOH and AME was recorded among the Section Infectoriae strains. These data show that a potential mycotoxin risk related to the consumption of Alternaria contaminated wheat is high.

Mycotoxigenic fungi contaminating wheat; toxicity of different Alternaria compacta strains

We studied mycotoxigenic fungi contaminating stored wheat grain, measured the toxins they secreted, and assessed their harmfulness. We focused on one common genus Alternaria, and chose 19 isolates representing A. compacta to study how different strains differed in their mycotoxin secretion and toxicity. Toxicity was assessed in a bioassay with a model bacteria Bacillus subtilis. All 19 A. compacta strains secreted toxins. Both the mycotoxin pattern and the fungal toxicity differed between the A. compacta stains. It seemed that some other toxins than alternariols or altenue acted as the main virulence factors of A. compacta against B. subtilis. We suggest that the most commonly studied mycotoxins do not necessarily indicate the toxicity of the fungi. The high variation in the amounts and toxins that different Alternaria species and strains secrete pose a challenge to the food supply chain.

Alternaria toxins in Argentinean wheat, bran, and flour

Alternaria species have been reported to infect a wide variety of vegetables, fruits, and cereal crops. Wheat is one of the most consumed cereal worldwide. A sensitive HPLC-DAD methodology was applied to quantify alternariol (AOH), alternariol methyl ether (AME) and tenuazonic acid (TeA) in 65 samples of whole wheat, bran, and flour. The extraction methodology allowed extracting the three toxins simultaneously. Limits of detection in wheat were 3.4, 4.5, and 0.5 µg kg^-1 for AOH, AME and TeA, respectively. For bran, these data were 3.1, 4.5, and 12 µg kg^-1 and for flour 50, 70, and 14 µg kg^-1, respectively. The studied recoveries were higher than 70% and RSD was below 10%. Wheat and bran samples showed low AOH and AME contamination compared to TeA. The averages levels found for TeA in wheat, bran and flour were 19,190, 16,760, and 7360 µg kg^-1, respectively.

Simple Approach for the Rapid Detection of Alternariol in Pear Fruit by Surface-Enhanced Raman Scattering with Pyridine-Modified Silver Nanoparticles

A simple method based on surface-enhanced Raman scattering (SERS) was developed for the rapid determination of alternariol (AOH) in pear fruits using an easily prepared silver-nanoparticle (AgNP) substrate. The AgNP substrate was modified by pyridine to circumvent the weak affinity of the AOH molecules to the silver surface and to improve the sensitivity of detection. Quantitative analysis was performed in AOH solutions at concentrations ranging from 3.16 to 316.0 μg/L, and the limit of detection was 1.30 μg/L. The novel method was also applied to the detection of AOH residues in pear fruits purchased from the market and in pear fruits that were artificially inoculated with Alternaria alternata. AOH was not found in any of the fresh fruit, whereas it resided in the rotten and inoculated fruits. Finally, the SERS method was cross validated against HPLC. It was revealed that the SERS method has great potential utility in the rapid detection of AOH in pear fruits and other agricultural products.

Mycotoxin production of Alternaria strains isolated from Korean barley grains determined by LC-MS/MS

Twenty-four Alternaria strains were isolated from barley grain samples. These strains were screened for the production of mycotoxins on rice medium using thin layer chromatography. All 24 strains produced at least one of the five mycotoxins (ALT, AOH, ATX-I, AME, and TeA). Three representative strains, namely EML-BLDF1-4, EML-BLDF1-14, and EML-BLDF1-18, were further analyzed using a new LC-MS/MS-based mycotoxin quantification method. This method was used to detect and quantify Alternaria mycotoxins. We used positive ion electrospray mass spectrometry with multiple reaction mode (MRM) for the simultaneous quantification of various Alternaria mycotoxins produced by these strains. Five Alternaria toxins (ALT, ATX-I, AOH, AME, and TeA) were detected and quantified. Sample preparation included methanol extraction, concentration, and injection into LC-MS/MS. Limit of detection ranged from 0.13 to 4μg/mL and limit of quantification ranged from 0.25 to 8μg/mL.

Alternaria alternata (Fr.) Keissl with mutation G143A in the Cyt b gene is the source of a difficult-to-control allergen

The saprotrophic fungus Alternaria alternata is widespread in the agro-environment and produces more than ten allergenic proteins, mostly protein Alt a 1. The frequency of the Alt a 1 gene was analyzed in a group of A. alternata isolates from winter wheat kernels obtained in Poland, and the effectiveness of various fungicides targeting the pathogen was evaluated. The Alt a 1 gene was identified in four of the seven tested isolates. A. alternata colonized 35.67% kernels on average, but its frequency increased in stored grain where the presence of epiphytes was noted on 23.09 to 51.38% kernels, and endophytes-in 26.21 to 42.01% of kernels. The efficacy of field-applied fungicides did not exceed 50%, despite the fact that A. alternata is highly sensitive to propiconazole, fenpropimorph, and tebuconazole under in vitro conditions. The analyzed isolates were characterized by limited sensitivity to azoxystrobin (EC₅₀ ranged from 0.505 to 1.350 μg cm^-3) due to a mutation at codon 143 of the CYT b gene, responsible for resistance to quinone outside inhibitor fungicides, which was noted in all isolates. The spread of A. alternata can be effectively controlled with suitable fungicides and by monitoring the prevalence of pathogenic isolates in the environment.

Isolation, characterization and toxicological potential of Alternaria-mycotoxins (TeA, AOH and AME) in different Alternaria species from various regions of India

Alternaria species produce various sorts of toxic metabolites during their active growth and causes severe diseases in many plants by limiting their productivity. These toxic metabolites incorporate various mycotoxins comprising of dibenzo-α-pyrone and some tetramic acid derivatives. In this study, we have screened out total 48 isolates of Alternaria from different plants belonging to different locations in India, on the basis of their pathogenic nature. Pathogenicity testing of these 48 strains on susceptible tomato variety (CO-3) showed 27.08% of the strains were highly pathogenic, 35.41% moderately pathogenic and 37.5% were less pathogenic. Phylogenetic analysis showed the presence of at least eight evolutionary cluster of the pathogen. Toxins (TeA, AOH and AME) were isolated, purified on the basis of column chromatography and TLC, and further confirmed by the HPLC-UV chromatograms using standards. The final detection of toxins was done by the LC-MS/MS analysis by their mass/charge ratio. The present study develops an approach to classify the toxicogenic effect of each of the individual mycotoxins on tomato plant and focuses their differential susceptibility to develop disease symptoms. This study represents the report of the natural occurrence and distribution of Alternaria toxins in various plants from India.

Alternaria Toxins: Potential Virulence Factors and Genes Related to Pathogenesis

Alternaria is an important fungus to study due to their different life style from saprophytes to endophytes and a very successful fungal pathogen that causes diseases to a number of economically important crops. Alternaria species have been well-characterized for the production of different host-specific toxins (HSTs) and non-host specific toxins (nHSTs) which depend upon their physiological and morphological stages. The pathogenicity of Alternaria species depends on host susceptibility or resistance as well as quantitative production of HSTs and nHSTs. These toxins are chemically low molecular weight secondary metabolites (SMs). The effects of toxins are mainly on different parts of cells like mitochondria, chloroplast, plasma membrane, Golgi complex, nucleus, etc. Alternaria species produce several nHSTs such as brefeldin A, tenuazonic acid, tentoxin, and zinniol. HSTs that act in very low concentrations affect only certain plant varieties or genotype and play a role in determining the host range of specificity of plant pathogens. The commonly known HSTs are AAL-, AK-, AM-, AF-, ACR-, and ACT-toxins which are named by their host specificity and these toxins are classified into different family groups. The HSTs are differentiated on the basis of bio-statistical and other molecular analyses. All these toxins have different mode of action, biochemical reactions and signaling mechanisms to cause diseases. Different species of Alternaria produced toxins which reveal its biochemical and genetic effects on itself as well as on its host cells tissues. The genes responsible for the production of HSTs are found on the conditionally dispensable chromosomes (CDCs) which have been well characterized. Different bio-statistical methods like basic local alignment search tool (BLAST) data analysis used for the annotation of gene prediction, pathogenicity-related genes may provide surprising knowledge in present and future.

Characterization of small-spored Alternaria from Argentinean crops through a polyphasic approach

Small-spored Alternaria have been isolated from a wide variety of food crops, causing both economic losses and human health risk due to the metabolites produced. Their taxonomy has been discussed widely, but no scientific consensus has been established in this field to date. Argentina is a major exporter of agricultural products, so it is essential to thoroughly understand the physiological behaviour of this pathogen in a food safety context. Thus, the objective of this work was to characterize small-spored Alternaria spp. obtained from tomato fruits, pepper fruits, wheat grains and blueberries from Argentina by a polyphasic approach involving metabolomic and phylogenetic analyses based on molecular and morphological characters. Morphological analysis divided the population studied into three groups; A. arborescens sp.-grp., A. tenuissima sp.-grp., and A. alternata sp.-grp. However, when these characters were simultaneously analysed with molecular data, no clearly separated groups were obtained. Haplotype network and phylogenetic analysis (both Bayesian and maximum parsimony) of a conserved region yielded the same result, suggesting that all isolates belong to the same species. Furthermore, no correlation could be established between morphological species-groups and a metabolite or group of metabolites synthesized. Thus, the whole set of analyses carried out in the present work supports the hypothesis that these small-spored Alternaria isolates from food belong to the same species. Identification at species level through classical morphology or modern molecular techniques does not seem to be a useful tool to predict toxicological risk in food matrices. The detection of any small-spored Alternaria from Section Alternaria (D.P. Lawr., Gannibal, Peever & B.M. Pryor 2013) in food implies a potential toxicological risk.

Alternaria Species and Their Associated Mycotoxins

The genus Alternaria includes more than 250 species. The traditional methods for identification of Alternaria species are based on morphological characteristics of the reproductive structures and sporulation patterns under controlled culture conditions. Cladistics analyses of "housekeeping genes" commonly used for other genera, failed to discriminate among the small-spored Alternaria species. The development of molecular methods achieving a better agreement with morphological differences is still needed. The production of secondary metabolites has also been used as a means of classification and identification. Alternaria spp. can produce a wide variety of toxic metabolites. These metabolites belong principally to three different structural groups: (1) the dibenzopyrone derivatives, alternariol (AOH), alternariol monomethyl ether (AME), and altenuene (ALT); (2) the perylene derivative altertoxins (ATX-I, ATX-II, and ATX II); and (3) the tetramic acid derivative, tenuazonic acid (TeA). TeA, AOH, AME, ALT, and ATX-I are the main. Certain species in the genus Alternaria produce host-specific toxins (HSTs) that contribute to their pathogenicity and virulence. Alternaria species are plant pathogens that cause spoilage of agricultural commodities with consequent mycotoxin accumulation and economic losses. Vegetable foods infected by Alternaria rot could introduce high amounts of these toxins to the human diet. More investigations on the toxic potential of these toxins and their hazard for human consumption are needed to make a reliable risk assessment of dietary exposure.

Spotlight on the Underdogs-An Analysis of Underrepresented Alternaria Mycotoxins Formed Depending on Varying Substrate, Time and Temperature Conditions

Alternaria (A.) is a genus of widespread fungi capable of producing numerous, possibly health-endangering Alternaria toxins (ATs), which are usually not the focus of attention. The formation of ATs depends on the species and complex interactions of various environmental factors and is not fully understood. In this study the influence of temperature (7 °C, 25 °C), substrate (rice, wheat kernels) and incubation time (4, 7, and 14 days) on the production of thirteen ATs and three sulfoconjugated ATs by three different Alternaria isolates from the species groups A. tenuissima and A. infectoria was determined. High-performance liquid chromatography coupled with tandem mass spectrometry was used for quantification. Under nearly all conditions, tenuazonic acid was the most extensively produced toxin. At 25 °C and with increasing incubation time all toxins were formed in high amounts by the two A. tenuissima strains on both substrates with comparable mycotoxin profiles. However, for some of the toxins, stagnation or a decrease in production was observed from day 7 to 14. As opposed to the A. tenuissima strains, the A. infectoria strain only produced low amounts of ATs, but high concentrations of stemphyltoxin III. The results provide an essential insight into the quantitative in vitro AT formation under different environmental conditions, potentially transferable to different field and storage conditions.

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.

Possibility of Alternaria toxins reduction by extrusion processing of whole wheat flour

This study represents the first report about possibility of reduction of Alternaria toxins in wheat using the extrusion process. Effects of extrusion processing parameters - moisture content (w=16, 20, 24g/100g), feeding rate (q=15, 20, 25kg/h), and screw speed (v=300, 390, 480rpm), on reduction rate of tenuazonic acid (TeA), alternariol (AOH) and alternariol monomethyl ether (AME), in whole wheat flour were investigated. Temperature ranged between 111.1 and 160.8°C, while the absolute pressure was from 0.17 to 0.23MPa. The simultaneous influence of w and v was the most important for TeA reduction (p<0.05), while v and q were the most influential for AOH reduction (p<0.01). Level of AME reduction was mostly influenced by w and v (p<0.10). Optimal parameters for reduction of all three Alternaria toxins were as follows: w=24g/100g, q=25kg/h, v=390rpm, with a reduction of 65.6% for TeA, 87.9% for AOH and 94.5% for AME.

Phenotypic and phylogenetic segregation of Alternaria infectoria from small-spored Alternaria species isolated from wheat in Germany and Russia

AIMS

To identify the taxonomic differences between phytopathogenic small-spored Alternaria strains isolated from wheat kernels in Germany and Russia by a polyphasic approach.

METHODS AND RESULTS

Ninety-five Alternaria (A.) strains were characterized by their colony colour, their three-dimensional sporulation patterns, mycotoxin production and phylogenetic relationships based on sequence variation in translation elongation factor 1-α (TEF1-α). The examination of toxin profiles and the phylogenetic features via TEF1-α resulted in two distinct clusters, in each case containing Alternaria infectoria isolates (92 and 96% respectively) in the first and the Alternaria alternata, Alternaria arborescens and Alternaria tenuissima isolates (77 and 79% respectively) in the other combined cluster. The production of Alternariol, Altertoxin and Altenuene has not been reported previously in the A. infectoria species group. The isolates from Germany and Russia differ slightly in species composition and mycotoxin production capacity.

CONCLUSIONS

We identified that the A. infectoria species group can be differentiated from the A. alternata, A. arborescens and A. tenuissima species group by colour, low mycotoxin production and by the sequence variation in TEF1-α gene.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results allow a reliable toxic risk assessment when detecting different Alternaria fungi on cereals.

Mycotoxins as antagonistic or supporting agents in the interaction between phytopathogenic Fusarium and Alternaria fungi

The role of mycotoxins in the microbial competition in an ecosystem or on the same host plant is still unclear. Therefore, a laboratory study was conducted to evaluate the influence of mycotoxins on growth and mycotoxin production of Fusarium and Alternaria fungi. Fusarium culmorum Fc13, Fusarium graminearum Fg23 and two Alternaria tenuissima isolates (At18 and At220) were incubated on wheat kernels supplemented with alternariol (AOH), tetramic acid derivates (TeA), deoxynivalenol (DON) and zearalenone (ZEA) in an in vitro test system. Fungal biomass was quantified by determining ergosterol content. Three Fusarium toxins (DON, nivalenol and ZEA) and three Alternaria toxins (AOH, alternariol methyl ether (AME) and altenuene) were analysed by HPLC-MS/MS. If Alternaria strains grew in wheat kernels spiked with Fusarium mycotoxins, their growth rates were moderately increased, their AOH and AME production was enhanced and they were simultaneously capable of degrading the Fusarium mycotoxins DON and ZEA. In contrast, both Fusarium strains behaved quite differently. The growth rate of Fc13 was not distinctly influenced, while Fg23 increased its growth in wheat kernels spiked with AOH. TeA depressed the ergosterol content in Fc13 as well as in Fg23. The DON production of Fc13 was slightly depressed, whereas the ZEA production was significantly increased. In contrast, Fg23 restricted its ZEA production. Both Fusarium strains were not capable of degrading the Alternaria mycotoxin AOH. Mycotoxins might play an important role in the interfungal competitive processes. They influence growth rates and mycotoxin production of the antagonistic combatants. The observed effects between phytopathogenic Alternaria and Fusarium strains and their mycotoxins aid the understanding of the complexity of microbial competitive behaviour in natural environments.