Occurrence of contamination and the reduction and transfer of Alternaria toxins in apples during processing

Alternaria spp. infect and accumulate various toxic secondary metabolites in apples, posing a threat to human and animal health. This study established instrumental analytical methods for six Alternaria toxins, systematically investigated the contamination levels of Alternaria toxins in apples and their reduction and transfer patterns during processing. Apples exhibited heightened disease susceptibility at 25 °C and produced 6 Alternaria toxins in different degrees, while Alternaria toxins were not observed within 4 cm of the symptomatic site. The transfer rate to pomace after juice extraction was higher than that in juice, with transfer rates ranging from 51.9 to 62.75 % for pomace and from 21.44 to 35.79 % for juice. Canning reduced Alternaria toxins in pulp, with the highest reduction rate of 93.3 % for tenuazonic acid. A total of four Alternaria toxins were detected in the testing of market samples of apple products, and none of the assessed total daily exposure doses of toxins ingested by humans through apple products exceeded the daily intake level recommended by the EFSA. The evaluation results indicate that the risk of dietary exposure of humans is relatively low through apple products. These findings provide valuable data and theoretical support for ensuring food safety in apples.

Development of a high-throughput UHPLC-MS/MS method for the analysis of Fusarium and Alternaria toxins in cereals and cereal-based food

A QuEChERS (quick, easy, cheap, effective, rugged, and safe)-based multi-mycotoxin method was developed, analyzing 24 (17 free and 7 modified) Alternaria and Fusarium toxins in cereals via ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). A modified QuEChERS approach was optimized for sample preparation. Quantification was conducted using a combination of stable isotope dilution analysis (SIDA) for nine toxins and matrix-matched calibration for ten toxins. Quantification via a structurally similar internal standard was conducted for four analytes. Alternariol-9-sulfate (AOH-9-S) was measured qualitatively. Limits of detection (LODs) were between 0.004 µg/kg for enniatin A1 (ENN A1) and 3.16 µg/kg for nivalenol (NIV), while the limits of quantification were between 0.013 and 11.8 µg/kg, respectively. The method was successfully applied to analyze 136 cereals and cereal-based foods, including 28 cereal-based infant food products. The analyzed samples were frequently contaminated with Alternaria toxins, proving their ubiquitous occurrence. Interestingly, in many of those samples, some modified Alternaria toxins occurred, mainly alternariol-3-sulfate (AOH-3-S) and alternariol monomethyl ether-3-sulfate (AME-3-S), thus highlighting the importance of including modified mycotoxins in the routine analysis as they may significantly add to the total exposure of their parent toxins. Over 95% of the analyzed samples were contaminated with at least one toxin. Despite the general contamination, no maximum or indicative levels were exceeded.

The combination of metabolome and transcriptome clarifies the inhibition of the Alternaria toxin accumulation by methyl ferulate

As one of the most typical pathogens in fruit postharvest diseases, Alternaria alternata (A. alternata) can produce Alternaria toxins (ATs) aggravating fruit decay and harming human health. In this study, ATs (tenuazonic acid, alternariol monomethyl ether, and alternariol) production was inhibited effectively by 200 and 8000 mg/L MF (methyl ferulate) in vitro and in vivo. 1-Octen-3-ol and 3-octanol were the potential iconic volatile organic compounds of ATs (R2 > 0.99). MF induced oxidative stress, resulting in physiological and metabolic disorders, membrane lipid oxidation and cell damage. It decreased precursors and energy supply by disturbing amino acid metabolism, ABC transporters, citrate cycle, pentose and glucuronate interconversions to regulate ATs synthesis. MF down-regulated the genes related to ATs synthesis (PksJ, AaTAS1, and OmtI), transport (AaMFS1 and MFS), and pathogenicity to affect ATs production and virulence. This study provided a theoretical basis for the control of ATs production.

Discovery of the Alternaria mycotoxins alterperylenol and altertoxin I as novel immunosuppressive and antiestrogenic compounds in vitro

Alternaria mycotoxins may pose significant challenges to food safety and public health due to the wide spectrum of reported adverse effects. Despite this, critical information on the immunomodulatory and antiestrogenic properties of most of these contaminants is still lacking. The present study aimed to identify the mycotoxins responsible for the immunosuppressive and antiestrogenic effects of a complex extract of Alternaria mycotoxins (CE) obtained by growing an Alternaria alternata strain on rice. Through a toxicity-guided fractionation procedure involving the production of CE-fractions by supercritical fluid chromatography and mycotoxin quantification by LC-MS/MS, the mycotoxins alternariol (AOH), tenuazonic acid (TeA), altertoxin I (ATX-I), and alterperylenol (ALTP) were identified as potential toxicologically relevant constituents contributing to the in vitro effects exerted by the extract. The assessment of the immunomodulatory effects, performed by applying the NF-κB reporter gene assay in THP1-Lucia™ monocytes, revealed the scarce contribution of AOH to the effects exerted by the CE. TeA showed no effect on the NF-κB pathway up to 250 µM, whereas ATX-I and ALTP suppressed the LPS-mediated pathway activation at concentrations ≥ 1 µM. The evaluation of antiestrogenic effects, performed in Ishikawa cells by applying the alkaline phosphatase assay, revealed the ability of ALTP (≥ 0.4 µM) and ATX-I (≥ 2 µM) to suppress the estrogen-dependent expression of enzyme activity. Given the risk of detrimental impacts stemming from alterations in endocrine and systemic immune responses by the investigated mycotoxins, further studies are needed to elucidate their underlying mechanisms of action and comprehensively evaluate the health risks posed by these toxins.

Biology, ecology, and epidemiology of Alternaria species affecting tomato: ground information for the development of a predictive model

Among pathogens that affect tomato, Alternaria spp. are important due to their implications in yield losses and the contamination of tomato products by mycotoxins. In this study, a systematic literature review was conducted to retrieve and analyze available data on the Alternaria-tomato pathosystem, with particular attention focused on the main biological processes included in the pathogen life cycle and mycotoxin production. We considered 110 papers (selected from initial 2,138 papers) on five Alternaria species that were historically related or recently identified to cause damage to tomato leafage and fruits. Published mathematical models related to Alternaria diseases in tomato were also screened based on their aim and development methods, highlighting the wide use of empirical approach. Retrieved information was also evaluated for applications in building a mechanistic, weather-driven model that incorporates the key steps of the pathogen life cycle. This systematic review highlights several knowledge gaps, including the effect of wetness on infection and environmental requirements for mycotoxin production, and suggests paths for further research especially for recently isolated species.

Natural resorcylic lactones derived from alternariol

In this overview, naturally occurring resorcylic lactones biosynthetically derived from alternariol and almost exclusively produced by fungi, are discussed with view on their isolation, structure, biological activities, biosynthesis, and total syntheses. This class of compounds consists until now of 127 naturally occurring compounds, with very divers structural motifs. Although only a handful of these toxins (i.e., alternariol and its 9-O-methyl ether, altenusin, dehydroaltenusin, altertenuol, and altenuene) were frequently found and isolated as fungal contaminants in food and feed and have been investigated in significant detail, further metabolites, which were much more rarely found as natural products, similarly show interesting biological activities.

Unraveling Interspecies Differences in the Phase I Hepatic Metabolism of Alternariol and Alternariol Monomethyl Ether: Closing Data Gaps for a Comprehensive Risk Assessment

The Alternaria mycotoxins alternariol (AOH) and alternariol 9-O-monomethyl ether (AME) are pervasive food contaminants known to exert adverse effects in vitro, yet their toxicokinetics remain inadequately understood. Thus, this study endeavors to elucidate the qualitative and quantitative aspects of the phase I metabolism of AOH and AME. To pursue this goal, reduced nicotinamide adenine dinucleotide phosphate (NADPH)-fortified porcine, rat, and human liver microsomes were incubated for 0-10 min with AOH or AME within a concentration range of 1-100 and 1-50 μM, respectively. The decline in the parent toxin concentration was monitored via liquid chromatography coupled to tandem mass spectrometry, whereas coupling to high-resolution mass spectrometry provided insights into the composition of the arising metabolic mixture. The collected quantitative data allowed us to calculate the hepatic intrinsic clearance rates of AOH and AME, marking a notable contribution to the field. Moreover, we unveiled interspecies differences in the pattern and rate of the phase I metabolism of the investigated mycotoxins. The presented findings lay the groundwork for physiologically based toxicokinetic modeling aimed at estimating local concentrations of these mycotoxins in specific organs, enhancing our understanding of their mode of action and adverse health effects.

The Velvet transcription factor PnVeA regulates necrotrophic effectors and secondary metabolism in the wheat pathogen Parastagonospora nodorum

The fungus Parastagonospora nodorum causes septoria nodorum blotch on wheat. The role of the fungal Velvet-family transcription factor VeA in P. nodorum development and virulence was investigated here. Deletion of the P. nodorum VeA ortholog, PnVeA, resulted in growth abnormalities including pigmentation, abolished asexual sporulation and highly reduced virulence on wheat. Comparative RNA-Seq and RT-PCR analyses revealed that the deletion of PnVeA also decoupled the expression of major necrotrophic effector genes. In addition, the deletion of PnVeA resulted in an up-regulation of four predicted secondary metabolite (SM) gene clusters. Using liquid-chromatography mass-spectrometry, it was observed that one of the SM gene clusters led to an accumulation of the mycotoxin alternariol. PnVeA is essential for asexual sporulation, full virulence, secondary metabolism and necrotrophic effector regulation.

Regulation of nitrogen utilization and mycotoxin biosynthesis by the GATA transcription factor AaAreA in Alternaria alternata

Alternaria alternata is a prevalent postharvest pathogen that generates diverse mycotoxins, notably alternariol (AOH) and alternariol monomethyl ether (AME), which are recurrent severe contaminants. Nitrogen sources modulate fungal growth, development, and secondary metabolism, including mycotoxin production. The GATA transcription factor AreA regulates nitrogen source utilization. However, little is known about its involvement in the regulation of nitrogen utilization in A. alternata. To examine the regulatory mechanism of AaAreA on AOH and AME biosynthesis in A. alternata, we analyzed the impact of diverse nitrogen sources on the fungal growth, conidiation and mycotoxin production. The use of a secondary nitrogen source (NaNO3) enhanced mycelial elongation and sporulation more than the use of a primary source (NH4Cl). NaNO3 favored greater mycotoxin accumulation than did NH4Cl. The regulatory roles of AaAreA were further clarified through gene knockout. The absence of AaAreA led to an overall reduction in growth in minimal media containing any nitrogen source except NH4Cl. AaAreA positively regulates mycotoxin biosynthesis when both NH4Cl and NaNO3 are used as nitrogen sources. Subcellular localization analysis revealed abundant nuclear transport when NaNO3 was the sole nitrogen source. The regulatory pathway of AaAreA was systematically revealed through comprehensive transcriptomic analyses. The deletion of AaAreA significantly impedes the transcription of mycotoxin biosynthetic genes, including aohR, pksI and omtI. The interaction between AaAreA and aohR, a pathway-specific transcription factor gene, demonstrated that AaAreA binds to the aohR promoter sequence (5'-GGCTATGGAAA-3'), activating its transcription. The expressed AohR regulates the expression of downstream synthase genes in the cluster, ultimately impacting mycotoxin production. This study provides valuable information to further understand how AreA regulates AOH and AME biosynthesis in A. alternata, thereby enabling the effective design of control measures for mycotoxin contamination.

Inhibitory Effect and Mechanism of Carvacrol against Black Mold Disease Agent Alternaria alternata in Goji Berries

Alternaria alternata, as a main decay fungus of goji berry, can produce mycotoxins such as alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TeA). Carvacrol (CVR) has exhibited a broad-spectrum antifungal activity in vitro. We assumed that CVR can also be applied to control Alternaria rot on goji berries and mycotoxins produced by the pathogens. To investigate whether CVR impacts the accumulation of mycotoxins and cell membrane damage of A. alternata, the antifungal activity of CVR on the fungal growth and mycotoxin production was evaluated in this study. The results showed that the minimum inhibitory concentration (MIC) of CVR against A. alternata was 0.12 µL/mL. Meanwhile, the destruction of plasma membrane integrity, cytoplasmic leakage, intracellular oxidative damage, and inhibitory effect in vivo were also observed in A. alternata treated with CVR. Moreover, CVR significantly reduced the accumulation of AOH, AME, and TeA. Transcriptomic profiling was performed by means of comparative RNA-Seq analysis to research the gene expression level of A. alternata, which attested to significant changes in nitrogen metabolism, carbon utilization, fatty acid oxidation, and antioxidant enzymes in CVR-treated A. alternata. This study suggests a new understanding of the molecular mechanism of response to CVR treatment in A. alternata, indicating that CVR is a novel antifungal agent with the potential to be applied to various fungi.

The characteristics, occurrence, and toxicological effects of alternariol: a mycotoxin

Alternaria species are mycotoxin-producing fungi known to infect fresh produce and to cause their spoilage. Humans get exposed to fungal secondary metabolites known as mycotoxin via the ingestion of contaminated food. Alternariol (AOH) (C14H10O5) is an isocoumarins produced by different species of Alternaria including Alternaria alternata. AOH is often found in grain, fruits and fruits-based food products with high levels in legumes, nuts, and tomatoes. AOH was first discovered in 1953, and it is nowadays linked to esophagus cancer and endocrine disruption due to its similarity to estrogen. Although considered as an emerging mycotoxin with no regulated levels in food, AOH occurs in highly consumed dietary products and has been detected in various masked forms, which adds to its occurrence. Therefore, this comprehensive review was developed to give an overview on recent literature in the field of AOH. The current study summarizes published data on occurrence levels of AOH in different food products in the last ten years and evaluates those levels in comparison to recommended levels by the regulating entities. Such surveillance facilitates the work of health risk assessors and highlights commodities that are most in need of AOH levels regulation. In addition, the effects of AOH on cells and animal models were summarized in two tables; data include the last two-year literature studies. The review addresses also the main characteristics of AOH and the possible human exposure routes, the populations at risk, and the effect of anthropogenic activities on the widespread of the mycotoxin. The commonly used detection and control methods described in the latest literature are also discussed to guide future researchers to focus on mitigating mycotoxins contamination in the food industry. This review aims mainly to serve as a guideline on AOH for mycotoxin regulation developers and health risk assessors.

Alternariol Monomethyl-Ether Induces Toxicity via Cell Death and Oxidative Stress in Swine Intestinal Epithelial Cells

Alternariol monomethyl-ether (AME), together with altenuene and alternariol, belongs to the Alternaria mycotoxins group, which can contaminate different substrates, including cereals. The aim of the present study was to obtain a deeper understanding concerning the effects of AME on pig intestinal health using epithelial intestinal cell lines as the data concerning the possible effects of Alternaria toxins on swine are scarce and insufficient for assessing the risk represented by Alternaria toxins for animal health. Our results have shown a dose-related effect on IPEC-1 cell viability, with an IC50 value of 10.5 μM. Exposure to the toxin induced an increase in total apoptotic cells, suggesting that AME induces programmed cell death through apoptosis based on caspase-3/7 activation in IPEC-1 cells. DNA and protein oxidative damage triggered by AME were associated with an alteration of the antioxidant response, as shown by a decrease in the enzymatic activity of catalase and superoxide dismutase. These effects on the oxidative response can be related to an inhibition of the Akt/Nrf2/HO-1 signaling pathway; however, further studies are needed in order to validate these in vitro data using in vivo trials in swine.

The mechanism behind tenuazonic acid-mediated inhibition of plant plasma membrane H+-ATPase and plant growth

The increasing prevalence of herbicide-resistant weeds has led to a search for new herbicides that target plant growth processes differing from those targeted by current herbicides. In recent years, some studies have explored the use of natural compounds from microorganisms as potential new herbicides. We previously demonstrated that tenuazonic acid (TeA) from the phytopathogenic fungus Stemphylium loti inhibits the plant plasma membrane (PM) H+-ATPase, representing a new target for herbicides. In this study, we further investigated the mechanism by which TeA inhibits PM H+-ATPase and the effect of the toxin on plant growth using Arabidopsis thaliana. We also studied the biochemical effects of TeA on the PM H+-ATPases from spinach (Spinacia oleracea) and A. thaliana (AHA2) by examining PM H+-ATPase activity under different conditions and in different mutants. Treatment with 200 μM TeA-induced cell necrosis in larger plants and treatment with 10 μM TeA almost completely inhibited cell elongation and root growth in seedlings. We show that the isoleucine backbone of TeA is essential for inhibiting the ATPase activity of the PM H+-ATPase. Additionally, this inhibition depends on the C-terminal domain of AHA2, and TeA binding to PM H+-ATPase requires the Regulatory Region I of the C-terminal domain in AHA2. TeA likely has a higher binding affinity toward PM H+-ATPase than the phytotoxin fusicoccin. Finally, our findings show that TeA retains the H+-ATPase in an inhibited state, suggesting that it could act as a lead compound for creating new herbicides targeting the PM H+-ATPase.

Aptamer functionalized magnetic hydrophobic polymer with synergetic effect for enhanced adsorption of alternariol from wheat

A new adsorbent based on aptamer functionalized magnetic hydrophobic polymer (MHbPA) was developed for specific and efficient adsorption of alternariol (AOH). Through the synergistic effect of aptamer-AOH affinity and hydrophobic interaction of polymer, enhanced adsorption properties had been realized, in which AOH aptamer was the first selected through capture-SELEX with good specificity and affinity, and the targeting polymer was designed based on the hydrophobicity of AOH to increase the interaction. The proposed MHbPA demonstrated a high adsorption capacity of 187.6 ng/mg for AOH. The adsorption behavior was considered as Langmuir adsorption model and pseudo-secondary kinetic adsorption model. Notably, the adsorption of AOH in wheat powder samples could be accomplished within 10 mins with acceptable recoveries. The as designed adsorbent with synergistic effect provides new insights into the development of enhanced pretreatment materials for mycotoxin monitoring in complex food matrices with specific aptamer and targeting polymer.

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.

Occurrence of Alternaria secondary metabolites in milling oats and its de-hulled fractions from harvest years 2017 to 2021

In this study, secondary metabolites produced by Alternaria were investigated for their presence in milling oats. For this purpose, pre-cleaned milling oat samples (n = 193), intended for human consumption, out of harvest years 2017 to 2021 originating from different northern European countries were analysed by LC-MS/MS. Alternariol and alternariol methyl ether were positively identified in 38% of the samples with mean values of 2.1 µg/kg and 1.2 µg/kg, respectively. The highest concentrations of 50.5 µg/kg alternariol and 24.2 µg/kg of alternariol methyl ether were detected in a Latvian sample. Tenuazonic acid was found in 45% of all samples, with a mean concentration of 28.9 µg/kg and a maximum concentration of 1430 µg/kg, also in a Latvian sample. Tentoxin was detected in 49% of all samples with a mean value of 1.7 µg/kg. The Alternaria metabolite most frequently detected in 96% of all samples was infectopyrone with a mean concentration of 593 µg/kg and a maximum value reaching up to 3990 µg/kg in a German sample. In addition, eight oat samples were selected to investigate to what extent the Alternaria metabolites are distributed between the oat hulls and the oat kernels. After de-hulling, approximately 23% of Alternaria metabolites were found in the remaining oat kernels. According to the results, alternariol, infectopyrone and altersetin were present in the kernels with the lowest proportion of 10%-20% on average, respectively. The values for tentoxin showed that about 60% of tentoxin was contained in the hulls, while almost 40% remained in the oat kernel. This suggests that potential health risks posed by Alternaria secondary metabolites and metabolites of other fungal genera in milling oats can be reduced by de-hulling.

Sensitive and selective alternariol analysis by a newly developed monoclonal antibody-based immunoassay

Alternariol is a toxic secondary metabolite produced by Alternaria fungi. Nowadays, this mycotoxin can be found in many products of plant origin at concerning concentrations. The aim of the present study was to develop a highly sensitive and selective immunochemical method for the analysis of alternariol. To this end, hapten synthesis was carried out from the scratch and specific high-affinity monoclonal antibodies to alternariol were generated by using, for the first time, alternariol bioconjugates with unambiguous linker tethering sites. A novel indirect enzyme-linked immunosorbent assay that incorporated a rationally designed heterologous conjugate was developed. The optimized assay showed an outstanding half-maximal inhibition concentration for alternariol below 0.04 ng/mL, and no cross-reactivity with alternariol monomethyl ether was observed. Very good recovery values and coefficients of variation were obtained from the analysis of alternariol-fortified fruit and cereal flour samples. Finally, alternariol was quantitatively determined in pears that had been previously infected with Alternaria alternata, showing excellent correlation with liquid chromatography results.

Fungal and Toxin Contaminants in Cereal Grains and Flours: Systematic Review and Meta-Analysis

Cereal grains serve as the cornerstone of global nutrition, providing a significant portion of humanity's caloric requirements. However, the presence of fungal genera, such Fusarium, Penicillium, Aspergillus, and Alternaria, known for their mycotoxin-producing abilities, presents a significant threat to human health due to the adverse effects of these toxins. The primary objective of this study was to identify the predominant fungal contaminants in cereal grains utilized in breadmaking, as well as in flour and bread. Moreover, a systematic review, including meta-analysis, was conducted on the occurrence and levels of mycotoxins in wheat flour from the years 2013 to 2023. The genera most frequently reported were Fusarium, followed by Penicillium, Aspergillus, and Alternaria. Among the published reports, the majority focused on the analysis of Deoxynivalenol (DON), which garnered twice as many reports compared to those focusing on Aflatoxins, Zearalenone, and Ochratoxin A. The concentration of these toxins, in most cases determined by HPLC-MS/MS or HPLC coupled with a fluorescence detector (FLD), was occasionally observed to exceed the maximum limits established by national and/or international authorities. The prevalence of mycotoxins in flour samples from the European Union (EU) and China, as well as in foods intended for infants, exhibited a significant reduction compared to other commercial flours assessed by a meta-analysis investigation.

Untargeted metabolomic analyses support the main phylogenetic groups of the common plant-associated Alternaria fungi isolated from grapevine (Vitis vinifera)

Alternaria, a cosmopolitan fungal genus is a dominant member of the grapevine (Vitis vinifera) microbiome. Several Alternaria species are known to produce a variety of secondary metabolites, which are particularly relevant to plant protection and food safety in field crops. According to previous findings, the majority of Alternaria species inhabiting grapevine belong to Alternaria sect. Alternaria. However, the phylogenetic diversity and secondary metabolite production of the distinct Alternaria species has remained unclear. In this study, our aim was to examine the genetic and metabolic diversity of endophytic Alternaria isolates associated with the above-ground tissues of the grapevine. Altogether, 270 Alternaria isolates were collected from asymptomatic leaves and grape clusters of different grapevine varieties in the Eger wine region of Hungary. After analyses of the nuclear ribosomal DNA internal transcribed spacer (ITS) and RNA polymerase second largest subunit (rpb2) sequences, 170 isolates were chosen for further analyses. Sequences of the Alternaria major allergen gene (Alt a 1), endopolygalacturonase (endoPG), OPA10-2, and KOG1058 were also included in the phylogenetic analyses. Identification of secondary metabolites and metabolite profiling of the isolates were performed using high-performance liquid chromatography (HPLC)-high-resolution tandem mass spectrometry (HR-MS/MS). The multilocus phylogeny results revealed two distinct groups in grapevine, namely A. alternata and the A. arborescens species complex (AASC). Eight main metabolites were identified in all collected Alternaria isolates, regardless of their affiliation to the species and lineages. Multivariate analyses of untargeted metabolites found no clear separations; however, a partial least squares-discriminant analysis model was able to successfully discriminate between the metabolic datasets from isolates belonging to the AASC and A. alternata. By conducting univariate analysis based on the discriminant ability of the metabolites, we also identified several features exhibiting large and significant variation between A. alternata and the AASC. The separation of these groups may suggest functional differences, which may also play a role in the functioning of the plant microbiome.

Mechanisms of Alternaria pathogenesis in animals and plants

Alternaria species are cosmopolitan fungi darkly pigmented by melanin that infect numerous plant species causing economically important agricultural spoilage of various food crops. Alternaria spp. also infect animals, being described as entomopathogenic fungi but also infecting warm-blooded animals, including humans. Their clinical importance in human health, as infection agents, lay in the growing number of immunocompromised patients. Moreover, Alternaria spp. are considered some of the most abundant and potent sources of airborne sensitizer allergens causing allergic respiratory diseases, as severe asthma. Among the numerous strategies deployed by Alternaria spp. to attack their hosts, the production of toxins, carrying critical concerns to public health as food contaminant, and the production of hydrolytic enzymes such as proteases, can be highlighted. Alternaria proteases also trigger allergic symptoms in individuals with fungal sensitization, acting as allergens and facilitating antigen access to the host subepithelium. Here, we review the current knowledge about the mechanisms of Alternaria pathogenesis in plants and animals, the strategies used by Alternaria to cope with the host defenses, and the involvement Alternaria allergens and mechanisms of sensitization.

Evaluation of the efficacy of ozonated olive oil for controlling the growth of Alternaria alternata and its toxins

Toxigenic fungi infect fruits and vegetables either during harvest or storage and create mycotoxins as secondary metabolites, which pose a serious threat to human and animal health throughout the food chain. Therefore, the objective of this study was to determine the inhibitory effect of OZO against the growth and spore germination of the Alternaria alternata fungal strain. Additionally, evaluation of the synthesis inhibition of Alternaria toxins (ATs), among which are alternariol (AOH), alternariol-9-methyl ether (AME), and tenuazonic acid (TeA) in the potato dextrose broth (PDB) medium and orange fruit after harvest. The results indicated that the inhibition zone was 29.0 ± 1.2 mm at 20 mg/L of OZO. The MIC and MFC values were recorded at 0.186 and 1.57 mg/mL, respectively. In this regard, OZO prevented conidia germination at 98.8% with the treatment of 5 mg/mL. OZO at 20 mg/mL was efficacious in producing a high loss in ATs production in the PDB medium, reaching 73.4, 76, and 67.1% for AOH, AME, and TeA, respectively. In addition, OZO prevents the biosynthesis of AOH and AME during the storage of orange fruits compared with the positive control sample. In contrast, 20 mg/mL reduced TeA accumulation and the appearance of Alternaria brown spot (ABS) in orange. To the best of our knowledge, this is the first report that studies OZO to control ATs in vitro in orange fruits.

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.

Uncovering Phytotoxic Compounds Produced by Colletotrichum spp. Involved in Legume Diseases Using an OSMAC-Metabolomics Approach

Different fungal species belonging to the Colletotrichum genus cause anthracnose disease in a range of major crops, resulting in huge economic losses worldwide. Typical symptoms include dark, sunken lesions on leaves, stems, or fruits. Colletotrichum spp. have synthesized, in vitro, a number of biologically active and structurally unusual metabolites that are involved in their host's infection process. In this study, we applied a one strain many compounds (OSMAC) approach, integrated with targeted and non-targeted metabolomics profiling, to shed light on the secondary phytotoxic metabolite panels produced by pathogenic isolates of Colletotrichum truncatum and Colletotrichum trifolii. The phytotoxicity of the fungal crude extracts was also assessed on their primary hosts and related legumes, and the results correlated with the metabolite profile that arose from the different cultural conditions. To the best of our knowledge, this is the first time that the OSMAC strategy integrated with metabolomics approaches has been applied to Colletotrichum species involved in legume diseases.

Hazard characterisation for significant mycotoxins in food

This review updates the current status of activities related to hazard characterisation for mycotoxins, with special reference to regulatory work accomplished within the European Union. Because the relevant information on these topics is widely scattered in the scientific literature, this review intends to provide a condensed overview on the most pertinent aspects. Human health risk assessment is a procedure to estimate the nature and potential for harmful effects of mycotoxins on human health due to exposure to them via contaminated food. This assessment involves hazard identification, hazard characterisation, exposure assessment, and risk characterisation. Mycotoxins covered in this review are aflatoxins, ochratoxin A, cyclopiazonic acid, citrinin, trichothecenes (deoxynivalenol, nivalenol, T-2, and HT-2 toxins), fumonisins, zearalenone, patulin, and ergot alkaloids. For mycotoxins with clear genotoxic/carcinogenic properties, the focus is on the margin of exposure approach. One of its goals is to document predictive characterisation of the human hazard, based on studies in animals using conditions of low exposure. For the other, non-genotoxic toxins, individual 'no adverse effect levels' have been established, but structural analogues or modified forms may still complicate assessment. During the process of hazard characterisation, each identified effect is assessed for human relevance. The estimation of a 'safe dose' is the hazard characterisation endpoint. The final aim of all of these activities is to establish a system, which is able to minimise and control the risk for the consumer from mycotoxins in food. Ongoing research on mycotoxins constantly comes up with new findings, which may have to be implemented into this system.

Root uptake and metabolization of Alternaria toxins by winter wheat plants using a hydroponic system

Fungi of the genus Alternaria are ubiquitous in the environment. Their mycotoxins can leach out of contaminated plants or crop debris into the soil entering the plant via the roots. We aim to evaluate the importance of this entry pathway and its contribution to the overall content of Alternaria toxins (ATs) in wheat plants to better understand the soil-plant-phytopathogen system. A hydroponic cultivation system was established and wheat plants were cultivated for up to two weeks under optimal climate conditions. One half of the plants was treated with a nutrient solution spiked with alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TeA), whereas the other half of the plants was cultivated without mycotoxins. Plants were harvested after 1 and 2 weeks and analyzed using a QuEChERS-based extraction and an in-house validated LC-MS/MS method for quantification of the ATs in roots, crowns, and leaves separately. ATs were taken up by the roots and transported throughout the plant up to the leaves after 1 as well as 2 weeks of cultivation with the roots showing the highest ATs levels followed by the crowns and the leaves. In addition, numerous AOH and AME conjugates like glucosides, malonyl glucosides, sulfates, and di/trihexosides were detected in different plant compartments and identified by high-resolution mass spectrometry. This is the first study demonstrating the uptake of ATs in vivo using a hydroponic system and whole wheat plants examining both the distribution of ATs within the plant compartments and the modification of ATs by the wheat plants.

Biocontrol potential of lipopeptides produced by the novel Bacillus subtilis strain Y17B against postharvest Alternaria fruit rot of cherry

The use of synthetic fungicides against postharvest Alternaria rot adversely affects human health and the environment. In this study, as a safe alternative to fungicides, Bacillus subtilis strain Y17B isolated from soil exhibited significant antifungal activity against Alternaria alternata. Y17B was identified as B. subtilis based on phenotypic identification and 16S rRNA sequence analysis. To reveal the antimicrobial activity of this strain, a PCR-based study detected the presence of antifungal lipopeptide (LP) biosynthetic genes from genomic DNA. UPLC Q TOF mass spectrometry analysis detected the LPs surfactin (m/z 994.64, 1022.68, and 1026.62), iturin (m/z 1043.56), and fengycin (m/z 1491.85) in the extracted LP crude of B. subtilis Y17B. In vitro antagonistic study demonstrated the efficiency of LPs in inhibiting A. alternata growth. Microscopy (SEM and TEM) studies showed the alteration of the morphology of A. alternata in the interaction with LPs. In vivo test results revealed the efficiency of LPs in reducing the growth of the A. alternata pathogen. The overall results highlight the biocontrol potential of LPs produced by B. subtilis Y17B as an effective biological control agent against A. alternata fruit rot of cherry.

Stress Response to Climate Change and Postharvest Handling in Two Differently Pigmented Lettuce Genotypes: Impact on Alternaria alternata Invasion and Mycotoxin Production

Many species of Alternaria are important pathogens that cause plant diseases and postharvest rots. They lead to significant economic losses in agriculture and affect human and animal health due to their capacity to produce mycotoxins. Therefore, it is necessary to study the factors that can result in an increase in A. alternata. In this study, we discuss the mechanism by which phenol content protects from A. alternata, since the red oak leaf cultivar (containing higher phenols) showed lower invasion than the green one, Batavia, and no mycotoxin production. A climate change scenario enhanced fungal growth in the most susceptible cultivar, green lettuce, likely because elevated temperature and CO₂ levels decrease plant N content, modifying the C/N ratio. Finally, while the abundance of the fungi was maintained at similar levels after keeping the lettuces for four days at 4 °C, this postharvest handling triggered TeA and TEN mycotoxin synthesis, but only in the green cultivar. Therefore, the results demonstrated that invasion and mycotoxin production are cultivar- and temperature-dependent. Further research should be directed to search for resistant cultivars and effective postharvest strategies to reduce the toxicological risk and economic losses related to this fungus, which are expected to increase in a climate change scenario.

Temperature-dependent mycotoxins production investigation in Alternaria infected cherry by ultra-high performance liquid chromatography and Orbitrap high resolution mass spectrometry

For temperature-dependent Alternaria mycotoxins production analysis, cherry samples were inoculated with Alternaria sp. and incubated at two different temperatures (4 °C and 25 °C). Six Alternaria mycotoxins, including altenuene (ALT), alternariol monomethyl ether (AME), alternariol (AOH), altertoxin-I (ATX-I), tenuazonic acid (TeA), and tentoxin (TEN), in cherries were detected with integrated visible data-processing tools. Maximum concentration of these mycotoxins reached 71,862.2 μg/kg at 25 °C. Notably, considerable amount of TeA (290.4 μg/kg) was detected at 4 °C, which indicated that low temperature is not a safe storage condition for fruits. A total of 102 compounds were detected with a neutral loss of 162.0528 Da, and TeA-glucose was identified in this work. Based on MS/MS cosine similarity, products were verified and annotated with feature based molecular networking (FBMN) in global natural products social networking (GNPS). The results showed Alternaria mycotoxins in cherry samples were mainly demethylation, hydrogenation, and dehydration. This work revealed the production of Alternaria mycotoxins in cherries under different storage temperature, which will provide theoretical basis for the control of mycotoxin contamination in food commodities.

Fungal Contamination of Building Materials and the Aerosolization of Particles and Toxins in Indoor Air and Their Associated Risks to Health: A Review

It is now well established that biological pollution is a major cause of the degradation of indoor air quality. It has been shown that microbial communities from the outdoors may significantly impact the communities detected indoors. One can reasonably assume that the fungal contamination of the surfaces of building materials and their release into indoor air may also significantly impact indoor air quality. Fungi are well known as common contaminants of the indoor environment with the ability to grow on many types of building materials and to subsequently release biological particles into the indoor air. The aerosolization of allergenic compounds or mycotoxins borne by fungal particles or vehiculated by dust may have a direct impact on the occupant’s health. However, to date, very few studies have investigated such an impact. The present paper reviewed the available data on indoor fungal contamination in different types of buildings with the aim of highlighting the direct connections between the growth on indoor building materials and the degradation of indoor air quality through the aerosolization of mycotoxins. Some studies showed that average airborne fungal spore concentrations were higher in buildings where mould was a contaminant than in normal buildings and that there was a strong association between fungal contamination and health problems for occupants. In addition, the most frequent fungal species on surfaces are also those most commonly identified in indoor air, regardless the geographical location in Europe or the USA. Some fungal species contaminating the indoors may be dangerous for human health as they produce mycotoxins. These contaminants, when aerosolized with fungal particles, can be inhaled and may endanger human health. However, it appears that more work is needed to characterize the direct impact of surface contamination on the airborne fungal particle concentration. In addition, fungal species growing in buildings and their known mycotoxins are different from those contaminating foods. This is why further in situ studies to identify fungal contaminants at the species level and to quantify their average concentration on both surfaces and in the air are needed to be better predict health risks due to mycotoxin aerosolization.

Effect of different storage conditions on the stability and safety of almonds

Almond production in Portugal is of great importance for the economy of their main producing areas. However, the contamination of these nut fruits with fungi and mycotoxins poses a significant risk to food safety and security. This work intended to evaluate the influence of storage conditions on the microbial and mycotoxin stability and safety of almonds throughout long-term storage. Two almond varieties-Lauranne and Guara-were submitted to three different storage conditions, namely, 4°C with noncontrolled relative humidity (RH), 60% RH at 25°C, and 70% RH at 25°C, for a storage period of 9 months. Samples were collected after 0, 3, 6, and 9 months of storage and analyzed for microbial loads (aerobic mesophiles, yeasts, and molds), mold incidence and diversity, and mycotoxin contamination. In total, 26 species were identified belonging to 6 genera: Aspergillus, Cladosporium, Fusarium, Penicillium, Paecilomyces, and Talaromyces. For the variety Guara, mycotoxins related to Aspergillus sect. Flavi, such as aflatoxins, averufin, versicolorin C, and norsolorinic acid, were detected only after 9 months of storage at 70% and 60% RH. Penicillium mycotoxins, such as quinolactacin A and roquefortine C, were also detected. For the variety Lauranne, Penicillium mycotoxins were detected, such as citrinin, quinolactacins A and B, roquefortines C and D, cyclopenin, cyclopenol, penitrem A, viridicatin, and viridicatol. Mycotoxins related to Aspergillus, such as aspulvinone E, flavoglaucin, paspalin, asperglaucide, asperphenamate, cyclo(L-Pro-L-Tyr), and cyclo(L-Pro-L-Val), were also detected. PRACTICAL APPLICATION: (Optional, for JFS Research Articles ONLY) The quality of almonds depends on the storage period and the RH and temperature at which they are stored. Storage of almonds at 60% RH at 25°C is a good storage condition to maintain the stability and safety of nuts in terms of microbial and mycotoxin contaminations.

Effects of Bacillus amyloliquefaciens XJ-BV2007 on Growth of Alternaria alternata and Production of Tenuazonic Acid

Large amounts of processing tomato are grown in Xinjiang, China. Tomato black spot disease, caused by Alternaria spp., and the produced alternaria toxins in tomato products are posing risks to human health. In this study, we isolated a rhizospheric bacterium, XJ-BV2007, from tomato (Solanum lycopersicum) fields, which we identified as Bacillus amyloliquefaciens. We found that this bacterium has a strong antagonistic effect against Alternaria alternata and reduces the accumulation of alternaria toxins in tomatoes. According to the antifungal activity of the bacteria-free filtrate, we revealed that B. amyloliquefaciens XJ-BV2007 suppresses A. alternata by the production of antifungal metabolites. Combining semi-preparative high-performance liquid chromatography, we employed UPLC-QTOF-MS analysis and the Oxford cup experiment to find that fengycin plays an important role in inhibiting A. alternata. This paper firstly reported that B. amyloliquefaciens efficiently controls tomato black spot disease and mycotoxins caused by A. alternata. B. amyloliquefaciens XJ-BV2007 may provide an alternative biocontrol strain for the prevention of tomato black spot disease.

Perfume Guns: Potential of Yeast Volatile Organic Compounds in the Biological Control of Mycotoxin-Producing Fungi

Pathogenic fungi in the genera Alternaria, Aspergillus, Botrytis, Fusarium, Geotrichum, Gloeosporium, Monilinia, Mucor, Penicillium, and Rhizopus are the most common cause of pre- and postharvest diseases of fruit, vegetable, root and grain commodities. Some species are also able to produce mycotoxins, secondary metabolites having toxic effects on human and non-human animals upon ingestion of contaminated food and feed. Synthetic fungicides still represent the most common tool to control these pathogens. However, long-term application of fungicides has led to unacceptable pollution and may favour the selection of fungicide-resistant mutants. Microbial biocontrol agents may reduce the incidence of toxigenic fungi through a wide array of mechanisms, including competition for the ecological niche, antibiosis, mycoparasitism, and the induction of resistance in the host plant tissues. In recent years, the emission of volatile organic compounds (VOCs) has been proposed as a key mechanism of biocontrol. Their bioactivity and the absence of residues make the use of microbial VOCs a sustainable and effective alternative to synthetic fungicides in the management of postharvest pathogens, particularly in airtight environments. In this review, we will focus on the possibility of applying yeast VOCs in the biocontrol of mycotoxigenic fungi affecting stored food and feed.

Interactions of Mycotoxin Alternariol with Cytochrome P450 Enzymes and OATP Transporters

Alternariol (AOH) is an emerging mycotoxin produced by Alternaria strains. The acute toxicity of the mycotoxin is low; however, chronic exposure to AOH may result in the development of endocrine disruptor and/or carcinogenic effects. The toxicokinetic properties of AOH have barely been characterized. Therefore, in this study, we aimed to investigate its interactions with CYP (1A2, 2C9, 2C19, 2D6, and 3A4) enzymes and OATP (1A2, 1B1, 1B3, and 2B1) transporters employing in vitro enzyme assays and OATP overexpressing cells, respectively. Our results demonstrated that AOH is a strong inhibitor of CYP1A2 (IC₅₀ = 0.15 μM) and CYP2C9 (IC₅₀ = 7.4 μM). Based on the AOH depletion assays in the presence of CYP enzymes, CYP1A2 is mainly involved, while CYP2C19 is moderately involved in the CYP-catalyzed biotransformation of the mycotoxin. AOH proved to be a strong inhibitor of each OATP transporter examined (IC₅₀ = 1.9 to 5.4 μM). In addition, both direct and indirect assays suggest the involvement of OATP1B1 in the cellular uptake of the mycotoxin. These findings promote the deeper understanding of certain toxicokinetic interactions of AOH.

Identification and Toxicological Characterization of Alternaria japonica Strains

Fungi of the genus Alternaria are producers of biologically active compounds. Alternaria japonica is pathogenic to small radish and certain other crucifers, but has not been studied in sufficient detail. Discrepant data on its toxic metabolites are available in the literature, possibly because a limited set of nutritive substrates was used in culturing or species identification of the strains was incorrect. The objectives of this study were to accurately identify the Russian A. japonica strains and to assess the A. japonica toxigenic potential. Four Russian A. japonica strains were identified using a multifaceted approach, which included analyses of morphological characters (the diameter and morphology of colonies grown on the diagnostic media potato carrot agar (PCA) and yeast extract-glucose (YES) agar for one week), the conidial size, and the presence of chlamydospores), the nucleotide sequences of DNA markers (ITS and EF1α regions), and chemotaxonomic data (mycotoxin production). Biomass and extractive substance yields of A. japonica cultures were found to significantly depend on the composition of the liquid medium. Minor differences between the A. japonica strains were detected via metabolite profiling by HPLC/MS-UV. Extracts of A. japonica cultures exerted phytotoxic activity toward small radish leaves and cytotoxicity toward Paramecium caudatum to a level comparable with that of A. tenuissima extracts. Brassicicolin A, dihydrobrassicicolin A, and phomenins A and B, which are known for several species of the genus Alternaria, were identified in A. japonica extracts. Mycotoxins (alternariol, its methyl ether, tentoxin, tenuazonic acid, and altenuene), which are characteristic of the cosmopolitan species A. tenuissima, were not detected in cultures of the A. japonica strains. Extract toxicity and the yield of extractive substances were studied in the A. japonica strains, and strain MFP244011 proved promising as a producer of known and, presumably, new toxins upon culture on the M1D synthetic medium or semisynthetic liquid media (e.g., the Sabouraud medium).

Cytotoxicities of Co-occurring alternariol, alternariol monomethyl ether and tenuazonic acid on human gastric epithelial cells

Alternariol (AOH), alternariol monomethyl ether (AME) and tenuazonic acid (TeA) are the three major Alternaria toxin contaminants in food. In the present study, we conducted their single and combined toxicity analyses using human gastric epithelial cell line (GES-1) that was first exposed to the toxins when they entered the human body. By comparing the cytotoxicity IC50, we found that compared to several other mycotoxins with limit standards there was cytotoxicity DON > OTA > AME > AOH > ZEN > TeA. Further, we obtained combination index (CI)-isobologram equation by the Chou-Talalay method according to a toxin ratio of 1:1:2 and carried out the combined toxicity analysis of the three binary and ternary compounds, and the results showed that AOH + AME + TeA showed synergistic toxic effects. Based on the co-occurring status, we also carried out the combined toxicity analysis of AME and AOH at different ratios and found antagonistic effects at low cytotoxic concentrations as well as synergistic and additive effects at high concentrations. Also, we found that all three and their combinations caused apoptosis, activation of caspase-3 cleavage, activation of DNA damage pathways ATR-Chk1-P53 and ATM-Chk2-P53. In conclusion, we used GES-1 cells to inform the risk of coaction of AOH, AME, and TeA in dietary exposure.

Overview of Bioactive Fungal Secondary Metabolites: Cytotoxic and Antimicrobial Compounds

Microorganisms are known as important sources of natural compounds that have been studied and applied for different purposes in distinct areas. Specifically, in the pharmaceutical area, fungi have been explored mainly as sources of antibiotics, antiviral, anti-inflammatory, enzyme inhibitors, hypercholesteremic, antineoplastic/antitumor, immunomodulators, and immunosuppressants agents. However, historically, the high demand for new antimicrobial and antitumor agents has not been sufficiently attended by the drug discovery process, highlighting the relevance of intensifying studies to reach sustainable employment of the huge world biodiversity, including the microorganisms. Therefore, this review describes the main approaches and tools applied in the search for bioactive secondary metabolites, as well as presents several examples of compounds produced by different fungi species with proven pharmacological effects and additional examples of fungal cytotoxic and antimicrobial molecules. The review does not cover all fungal secondary metabolites already described; however, it presents some reports that can be useful at any phase of the drug discovery process, mainly for pharmaceutical applications.

Phylogeny and mycotoxin profiles of pathogenic Alternaria and Curvularia species isolated from date palm in southern Tunisia

Date palm (Phoenix dactylifera L.), is a widely cultivated crop across North Africa, with about 300 thousand tons of fruits produced per year, in Tunisia. A wide range of fungal pathogens has been associated with leaf spots of date palm, Alternaria species being the most frequently reported. Symptomatic leaves of Deglet Nour variety were randomly collected in six localities in Tunisia. We used a polyphasic approach to identify 45 Alternaria and five Curvularia strains isolated from date palm, confirming their pathogenicity. Sequencing of allergen Alt-a1, glyceraldehyde-3-phosphate dehydrogenase (gpd) and calmodulin genes allowed us to group 35 strains in Alternaria Section, and 10 strains in Ulocladioides section. Based on sequencing analyses of Internal Transcribed Spacer, gpd and elongation factor genomic regions, all Curvularia strains were identified as Curvularia spicifera. All Alternaria and Curvularia species tested on date palm plantlets proved to be pathogenic, fulfilling Koch's postulates. Although no significant differences were observed among the species, the highest mean disease severity index was observed in A. arborescens, while the lowest corresponded to C. spicifera. The capability of these strains to produce mycotoxins in vitro was evaluated. None of the A. consortialis strains produced any known Alternaria mycotoxin, whereas more than 80% of the strains included in Alternaria section Alternaria produced variable amounts of multiple mycotoxins such as alternariol, alternariol monomethyl ether, altenuene, tenuazonic acid and tentoxin. Curvularia spicifera strains produced detectable traces of fumonisins B. This work reports a first comprehensive multidisciplinary study of mycotoxigenic Alternaria species and C. spicifera associated with leaf spot disease on date palm.

Epidemic Identification of Fungal Diseases in Morchella Cultivation across China

True morels (Morchella, Pezizales) are world-renowned edible mushrooms (ascocarps) that are widely demanded in international markets. Morchella has been successfully artificially cultivated since 2012 in China and is rapidly becoming a new edible mushroom industry occupying up to 16,466 hectares in the 2021-2022 season. However, nearly 25% of the total cultivation area has annually suffered from fungal diseases. While a variety of morel pathogenic fungi have been reported their epidemic characteristics are unknown, particularly in regional or national scales. In this paper, ITS amplicon sequencing and microscopic examination were concurrently performed on the morel ascocarp lesions from 32 sites in 18 provinces across China. Results showed that Diploöspora longispora (75.48%), Clonostachys solani (5.04%), Mortierella gamsii (0.83%), Mortierella amoeboidea (0.37%) and Penicillium kongii (0.15%) were the putative pathogenic fungi. The long, oval, septate conidia of D. longispora was observed on all ascocarps. Oval asexual spores and sporogenic structures, such as those of Clonostachys, were also detected in C. solani infected samples with high ITS read abundance. Seven isolates of D. longispora were isolated from seven selected ascocarps lesions. The microscopic characteristics of pure cultures of these isolates were consistent with the morphological characteristics of ascocarps lesions. Diploöspora longispora had the highest amplification abundance in 93.75% of the samples, while C. solani had the highest amplification abundance in six biological samples (6.25%) of the remaining two sampling sites. The results demonstrate that D. longispora is a major culprit of morel fungal diseases. Other low-abundance non-host fungi appear to be saprophytic fungi infecting after D. longispora. This study provides data supporting the morphological and molecular identification and prevention of fungal diseases of morel ascocarps.

Mycotoxin Production and the Relationship between Microbial Diversity and Mycotoxins in Pyrus bretschneideri Rehd cv. Huangguan Pear

Mycotoxins are generated by a series of fungal pathogens in postharvest fruit, resulting in serious health threat to consumers and great economic loss to the fruit storage industry. The microbial differences between rotten and healthy fruit during storage and their relationship with mycotoxin production have not been fully studied. In this study, differences in microbial diversity between rotten and healthy fruit after 30 days of storage at ambient temperature were investigated using high-throughput sequencing technology in 'Huangguan' pear (Pyrus bretschneideri Rehd cv. Huangguan) harvested from five different producing regions of Hebei province, China. The bacterial genus Gluconobacter was much more abundant in rotten fruit (76.24%) than that in healthy fruit (32.36%). In addition, Komagataeibacter and Acetobacter were also relatively higher in abundance in rotten fruit. In contrast, bacterial genera Pantoea, Alistipes, Muribaculaceae, Lactobacillus, and Ruminococcaceae_UCG were found to be more abundant in healthy fruit. Fungal genera including Botryosphaeria, Colletotrichum, Valsa, Alternaria, Rosellinia, Fusarium, and Trichothecium were found to be abundant in rotten fruit. The results of principal coordinate analysis (PCoA) showed that there were significant differences in the microbial diversity of different regions. PAT (patulin) was detected in all rotten fruit samples, while tenuazonic acid (TeA), alternariol (AOH), and alternariolmonomethyl ether (AME) were only detected in samples collected from one region (Weixian). Canonical correlation analysis (CCA) and Pearson correlation analysis showed that the abundance of Alistipes and Pantoea were negatively correlated with the contents of PAT, suggesting that bacterial genera Alistipes and Pantoea have potential in reducing mycotoxin production in 'Huangguan' pear.

Rapid and sensitive detection of tenuazonic acid in agricultural by-products based on gold nano-flower lateral flow

Tenuazonic acid (TA) is a highly toxic mycotoxin mainly generated by the fungi of Alternaria genus and widely contaminates agricultural by-products. Given the threat of TA to food-security, it is very important to develop rapid and sensitive detection methods for TA monitoring. In this study, gold nano-particles (AuNP) with average diameter near 17.25 nm were prepared, and the developed AuNP-based strip has an assay time of 15 min with visual limit of detection (LOD) of 12.5 ng/ml and threshold of 100 ng/ml. To further improve sensitivity, multi-branched gold nano-flowers (AuNF) with average diameter near 50 nm were prepared and characterized by UV-VIS and TEM, and the established AuNF-based strip has visual LOD of 0.78 ng/ml and threshold of 50 ng/ml within 15 min. Both assays were applied to determine TA in apple juice and tomato ketchup, and the results were consistent with that of UHPLC-MS/MS. Thus, these assays could be applied for rapid determination of trace TA in real samples.

Molecular Characterization of Phospholipase C in Infection Structure Differentiation Induced by Pear Fruit Surface Signals, Stress Responses, Secondary Metabolism, and Virulence of Alternaria alternata

Fungal pathogens use plant surface physiochemical signals to trigger specific developmental processes. To assess the role of phospholipase C (PLC) in mediating plant stimuli sensing of Alternaria alternata, the function of three PLC genes was characterized by constructing ΔAaPLC mutants. Here we showed that fruit wax-coated surfaces significantly induced appressorium formation in A. alternata and mutants. Germination of ΔAaPLC mutants did not differ from the wild type. Deletion of AaPLC1 led to the decrease of appressorium formation and infected hyphae, but the degree of reduction varies between the different types of waxes, with the strongest response to pear wax. Appressorium formation and infected hyphae of the ΔAaPLC1 mutant on dewaxed onion epidermis mounted with pear wax (θ4) were reduced by 14.5 and 65.7% after 8 h incubation, while ΔAaPLC2 and ΔAaPLC3 formed the same infection hyphae as wild type. In addition, AaPLC1 mutation caused pleiotropic effects on fungal biological function, including growth deficiency, changes in stress tolerance, weakening of pathogenicity to the host, as well as destruction of mycotoxin synthesis. Both AaPLC2 and AaPLC3 genes were found to have some effects on stress response and mycotoxin production. Taken together, AaPLC genes differentially regulate the growth, stress response, pathogenicity, and secondary metabolism of A. alternata.

Concise Syntheses of Alternariol, Alternariol-9-monomethyl Ether and Their D3-Isotopologues

Alternariol (AOH) and alternariol-9-monomethyl ether (AME) are two secondary metabolites of Alternaria fungi which can be found in various foodstuffs like tomatoes, nuts, and grains. Due to their toxicity and potential mutagenic activity the need for the development of high-throughput methods for the supervision of AOH and AME levels is of increasing interest. As the availability of both native and labeled AOH and AME analytical standards is very limited, we herein present a novel and concise approach towards their synthesis by employing a ruthenium-catalyzed ortho-arylation as the key step. Finally, we demonstrate their suitability as internal standards in stable-isotope dilution assay (SIDA)-HPLC-MS/MS analysis, a technique commonly used for the quantification of natural products in food and feed.

General toxicity and genotoxicity of alternariol: a novel 28-day multi-endpoint assessment in male Sprague-Dawley rats

Alternariol (AOH) is one of the toxins of Alternaria, and it has been widely detected in a variety of foods. It has been reported to be cytotoxic, dermally toxic, genotoxic, and potentially carcinogenic in vitro. However, in vivo toxicity data are lacking. This study used a novel in vivo 28-day multi-endpoint (Pig-a assay + micronucleus test + comet assay) genotoxicity evaluation system to evaluate the general toxicity and genotoxicity of AOH. A total of 42 male Sprague-Dawley rats were randomly distributed into three AOH-treated groups (5.51, 10.03, and 22.05 µg/kg bw), one AOH high-dose recovery group (AOH-HR, 22.05 µg/kg bw), one positive control group (N-ethyl-N-nitrosourea, 40 mg/kg bw), and two vehicle control groups (corn oil and PBS). Treatments were administered by oral gavage for 28 consecutive days. Histopathological lesions were observed in the liver, kidney, and spleen in all AOH-treated groups. No statistical difference was found in each genotoxicity index within 28 days in the AOH-treated groups compared with those in the corn oil group. On day 42, in the AOH-HR group, the rate of Pig-a mutant phenotype reticulocytes (RET^CD59-) significantly increased. On day 56, both RET^CD59- and the rate of Pig-a mutant phenotype erythrocytes (RBC^CD59-) were significantly reduced. These findings indicated that AOH might cumulatively induce genetic mutations.

Cocktails of Mycotoxins, Phytoestrogens, and Other Secondary Metabolites in Diets of Dairy Cows in Austria: Inferences from Diet Composition and Geo-Climatic Factors

Dairy production is a pivotal economic sector of Austrian and European agriculture. Dietary toxins and endocrine disruptors of natural origin such as mycotoxins and phytoestrogens can affect animal health, reproduction, and productivity. This study characterized the profile of a wide spectrum of fungal, plant, and unspecific secondary metabolites, including regulated, emerging, and modified mycotoxins, phytoestrogens, and cyanogenic glucosides, in complete diets of lactating cows from 100 Austrian dairy farms. To achieve this, a validated multi-metabolite liquid chromatography/electrospray ionization−tandem mass spectrometric (LC/ESI−MS/MS) method was employed, detecting 155 of >800 tested metabolites. Additionally, the most influential dietary and geo-climatic factors related to the dietary mycotoxin contamination of Austrian dairy cattle were recognized. We evidenced that the diets of Austrian dairy cows presented ubiquitous contamination with mixtures of mycotoxins and phytoestrogens. Metabolites derived from Fusarium spp. presented the highest concentrations, were the most recurrent, and had the highest diversity among the detected fungal compounds. Zearalenone, deoxynivalenol, and fumonisin B1 were the most frequently occurring mycotoxins considered in the EU legislation, with detection frequencies >70%. Among the investigated dietary factors, inclusion of maize silage (MS) and straw in the diets was the most influential factor in contamination with Fusarium-derived and other fungal toxins and metabolites, and temperature was the most influential among the geo-climatic factors.

Fungal Species and Multi-Mycotoxin Associated with Post-Harvest Sorghum (Sorghum bicolor (L.) Moench) Grain in Eastern Ethiopia

Sorghum is the main staple food crop in developing countries, including Ethiopia. However, sorghum grain quantity and quality are affected by contaminating fungi both under field and post-harvest stage. The aim of the current study was to assessed fungal species and multi-mycotoxins associated with sorghum grain in post-harvest samples collected from eastern Ethiopia. Fungal genera of Aspergillus, Alternaria, Bipolaris, Fusarium, Mucor, Penicillium, and Rhizoctonia were recovered in the infected grain. A liquid chromatography-tandem mass spectrometric (LC-MS/MS) was used for quantification of multiple mycotoxins/fungal metabolites. Overall, 94 metabolites were detected and grouped into eight categories. All metabolites were detected either in one or more samples. Among major mycotoxins and derivatives, deoxynivalenol (137 μg/kg), zearalenone (121 μg/kg), ochratoxin A (115 μg/kg), and fumonisin B₁ (112 μg/kg) were detected with maximum concentrations, while aflatoxin B₁ had relatively lower concentrations (23.6 μg/kg). Different emerging mycotoxins were also detected, with tenuazonic acid (1515 μg/kg) occurring at the maximum concentration among Alternaria metabolites. Fusaric acid (2786 μg/kg) from Fusarium metabolites and kojic acid (4584 μg/kg) were detected with the maximum concentration among Fusarium and Aspergillus metabolites, respectively. Unspecific metabolites were recognized with neoechinulin A (1996 μg/kg) at the maximum concentration, followed by cyclo (L-Pro-L-Tyr) (574 μg/kg) and cyclo (L-Pro-L-Val) (410 μg/kg). Moreover, metabolites form other fungal genera and bacterial metabolites were also detected at varying levels. Apparently, the study revealed that sorghum grains collected across those districts were significantly contaminated with co-occurrences of several mycotoxins. Farmers should be the main target groups to be trained on the improved management of sorghum production.

Longitudinal Investigation of the Native Grass Hay from Storage to Market Reveals Mycotoxin-Associated Fungi

This study aimed to characterize the fungal diversity and mycotoxin concentrations of native grass hay in various storage periods. In the present study, the native grass hay samples were collected when stored for 0 d (D0 group), 30 d (D30 group), and 150 d (D150 group), respectively. Here, mycotoxin analyses combined with ITS gene sequence were performed to reveal the changes in response to the storage period. There were notable differences in deoxynivalenol and aflatoxin B1 concentrations among the three groups. Compared to the D150 group, the diversity of the fungal community was higher in the D0 and D30 groups, which indicating the diversity was significantly influenced by the storage period. No significant (p > 0.05) difference was observed among the three groups on the dominant phyla. Interestingly, a significant (p < 0.05) difference was also observed in Chactomella and Aspergillus among the three groups, the abundance of the Chactomella was significantly (p < 0.05) decreased and the abundance of Aspergillus was statistically (p < 0.05) increased in the D150 group. Correlation analysis of the association of fungi with mycotoxin could provide a comprehensive understanding of the structure and function of the fungal community. These results indicated that the good practices of storage are essential for the prevention of mycotoxin. The information contained in the present study is vital for the further development of strategies for hay storage with high quality in the harsh Mongolian Plateau ecosystem.