Alternaria in food products

Expansion of the multi-locus gene alignment approach to improve identification of the fungal species Alternaria alternata

Alternaria alternata is part of a genus comprised of over 600 different species that occur all over the world and cause damage to humans, plants and thereby to the economy. Yet, even though some species are causing tremendous issues, the past years have shown that assigning newly found isolates to known species was rather inconsistent. Most identifications are usually done on the basis of spore morphology, chemotype and molecular markers. In this work we used strains isolated from the wild as well as commercial strains of the DSMZ (German collection of microorganisms and cell cultures) as a reference, to show, that the variation within the Alternaria alternata species is comparable to the variation between different species of the genus Alternaria in regards to spore morphology and chemotype. We compared the different methods of identification and discerned the concatenation of multiple molecular markers as the deciding factor for better identification. Up until this point, usually a concatenation of two or three traditional molecular markers was used. Some of those markers being stronger some weaker. We show that the concatenation of five molecular markers improves the likeliness of a correct assignment, thus a better distinction between the different Alternaria species.

Integrating CRISPR-Cas12a and rolling circle-amplified G-quadruplex for naked-eye fluorescent "off-on" detection of citrus Alternaria

Alternaria is a plant pathogen that spreads globally and is prone to causing citrus brown spot disease and metabolizing mycotoxins, thus seriously hindering the development of this economic crop industry. Herein, a "label-free" and "turn on" visual fluorescent assay for citrus Alternaria based on CRISPR-Cas12a and rolling circle amplification (RCA) was described. Using ssDNA complementary to RCA primer as a trans-cleavage substrate for CRISPR-Cas12a, the two systems of CRISPR-Cas12a and RCA-amplified G-quadruplex were skillfully integrated. By using a portable light source for excitation, the positive sample produced obvious red fluorescence, while the negative sample remained almost colorless, making them easy to differentiate with the naked eye. In addition, the specificity was demonstrated by distinguishing Alternaria from other citrus disease related pathogens. Moreover, the practicality was verified by analyzing cultured Alternaria and Alternaria in actual citrus leaf and fruit samples. Therefore, this method may contribute to the on-site diagnosis of Alternaria.

Dietary mycotoxin exposure and human health risks: A protocol for a systematic review

BACKGROUND

Mycotoxins are toxic fungal secondary metabolites that contaminate a wide spectrum of essential foods worldwide, such as grain-based products, nuts and spices, causing adverse health effects pertaining to their carcinogenic, nephrotoxic and hepatotoxic nature, among others.

AIM

The aim of this systematic review (SR) is to systematically search for, appraise and synthesize primary research evidence to identify what is known about dietary mycotoxin-related health effects and what remains unknown, as well as the uncertainty around findings and the recommendations for the future.

SEARCH STRATEGY AND ELIGIBILITY CRITERIA

Search strategies, as well as eligibility criteria were structured according to a predefined PECO (population, exposure, comparison, and outcome) research question and developed in an iterative scoping process. Several bibliographic databases, including Embase, Cochrane Library, Pubmed, Web of Science Core Collection and Scopus, will be searched. Primary research on any measured or modelled dietary exposure to a single or multiple mycotoxins, and adverse human health outcomes (i.e. cancer, non-carcinogenic diseases, and reproductive & developmental adverse outcomes) will be included, and references will be imported into Covidence. In vitro, ex vivo, in silico, animal and review studies, as well as expert's opinions, secondary literature, conference abstracts, presentations, posters, book chapters, dissertations and studies involving non-dietary mycotoxin exposure, will be excluded.

STUDY SELECTION

Two independent reviewers will screen titles and abstracts, and review full-texts. Any disagreements will be resolved by a third reviewer based on two-third majority.

DATA EXTRACTION

Data from retained eligible studies will be extracted by the principal reviewer, and peer-checked by a second reviewer.

STUDY QUALITY ASSESSMENT

Eligible studies will be evaluated for risk of bias (Overall High-Quality Assessment Tool, OHAT) and certainty of evidence (Grading of Recommendations Assessment, Development and Evaluation, GRADE).

EVIDENCE SYNTHESIS

A detailed summary of the included studies will be provided within a tabular format and narratively discussed. Heat maps will be constructed to provide information on available knowledge (gaps), and a meta-analysis may be performed based on the variability in predefined PECO elements and depending on the heterogeneity of studies.

CONCLUSION

This protocol describes the methodology for the conduct of a SR on mycotoxin-related human health risks, that could guide future research and inform regulatory decisions, as emphasized by the European Commission within the field of regulatory risk assessment for emerging chemicals.

Hydrogel Digital LAMP with Suppressed Nonspecific Amplification for Rapid Diagnostics of Fungal Disease in Fresh Fruits

Fungal disease, mainly caused by Alternaria alternata infection, can generate severe economic losses and health hazards. However, rapid nucleic acid test without nonspecific reaction still remains challenging. Here, we reported the hydrogel digital loop-mediated isothermal amplification (HdLAMP) with suppressed nonspecific amplification for rapid diagnosis of fungi in fresh fruits. The introduction of hydrogel offered a simple platform to achieve absolute quantification. By breaking the 3'end G-C anchor, the nonspecific amplification of primers could be suppressed, while the specific positive reaction in HdLAMP was not affected. This method could be applied for A. alternata detection in 9 min with excellent performances in speed, specificity, reproducibility, sensitivity, and detection limit down to a single copy. Finally, the real diseased jujubes during postharvest storage were successfully diagnosed as an A. alternata infection. HdLAMP promotes the molecular diagnosis of fungal diseases and broadens the application of hydrogels in the agricultural and food industry.

Characterization of Alternaria alternata and Alternaria scrophulariae Brown Spot in Colombian quinoa (Chenopodium quinoa)

Alternaria is a saprophytic and opportunistic fungus with a worldwide distribution that can affect the quality of various agricultural products, such as fruits, cereals, and pseudocereals. This research was carried out to investigate the population of this genus associated with quinoa cultivation in plots located in the Boyacá department (Colombia), the country's third-largest quinoa-producing department. The present study found 17 Alternaria isolates, of which 13 were identified as A. alternata and 4 as A. scrophulariae (formerly A. conjuncta) employed molecular markers of internal transcribed spacer (ITS) region and translation elongation factor 1α (TEF-1α). In the pathogenicity test under greenhouse conditions, all the Alternaria isolates showed some degree of pathogenicity on Piartal quinoa cultivar plants although no significant differences were found in isolates. The severity indices ranged from 2 to 5, and the percentage of affected leaves per plant ranged between 15% and 40%. This fungus affected the foliar tissue of quinoa, resulting in chlorotic and necrotic spots, symptoms that can generate a reduction in the quality and productivity of crops. This is the first time that the pathogenicity of Alternaria spp. in the Piartal variety has been described and the first report of this genera in quinoa crops of Colombia.

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.

Diversity of Mycotoxins and Other Secondary Metabolites Recovered from Blood Oranges Infected by Colletotrichum, Alternaria, and Penicillium Species

This study identified secondary metabolites produced by Alternaria alternata, Colletotrichum gloeosporioides, and Penicillium digitatum in fruits of two blood orange cultivars before harvest. Analysis was performed by UHPLC-Q-TOF-MS. Three types of fruits were selected, asymptomatic, symptomatic showing necrotic lesions caused by hail, and mummified. Extracts from peel and juice were analyzed separately. Penicillium digitatum was the prevalent species recovered from mummified and hail-injured fruits. Among 47 secondary metabolites identified, 16, 18, and 13 were of A. alternata, C. gloeosporioides, and P. digitatum, respectively. Consistently with isolations, indicating the presence of these fungi also in asymptomatic fruits, the metabolic profiles of the peel of hail-injured and asymptomatic fruits did not differ substantially. Major differences were found in the profiles of juice from hail-injured and mummified fruits, such as a significant higher presence of 5,4-dihydroxy-3,7,8-trimethoxy-6C-methylflavone and Atrovenetin, particularly in the juice of mummified fruits of the Tarocco Lempso cultivar. Moreover, the mycotoxins patulin and Rubratoxin B were detected exclusively in mummified fruits. Patulin was detected in both the juice and peel, with a higher relative abundance in the juice, while Rubratoxin B was detected only in the juice. These findings provide basic information for evaluating and preventing the risk of contamination by mycotoxins in the citrus fresh fruit supply chain and juice industry.

Phenolic-Rich Extracts from Circular Economy: Chemical Profile and Activity against Filamentous Fungi and Dermatophytes

Fungal infections represent a relevant issue in agri-food and biomedical fields because they could compromise quality of food and humans' health. Natural extracts represent a safe alternative to synthetic fungicides and in the green chemistry and circular economy scenario, agro-industrial wastes and by-products offer an eco-friendly source of bioactive natural compounds. In this paper, phenolic-rich extracts from Olea europaea L. de-oiled pomace, Castanea sativa Mill. wood, Punica granatum L. peel, and Vitis vinifera L. pomace and seeds were characterized by HPLC-MS-DAD analysis. Finally, these extracts were tested as antimicrobial agents against pathogenic filamentous fungi and dermatophytes such as Aspergillus brasiliensis, Alternaria sp., Rhizopus stolonifer, and Trichophyton interdigitale. The experimental results evidenced that all extracts exhibited a significant growth inhibition for Trichophyton interdigitale. Punica granatum L., Castanea sativa Mill., and Vitis vinifera L. extracts showed a high activity against Alternaria sp. and Rhizopus stolonifer. These data are promising for the potential applications of some of these extracts as antifungal agents in the food and biomedical fields.

Microbial and Biochemical Profile of Different Types of Greek Table Olives

Analysis of table olives microbiome using next-generation sequencing has enriched the available information about the microbial community composition of this popular fermented food. In this study, 16S and 18S rRNA sequencing was performed on table olives of five Greek popular cultivars, Halkidikis, Thassou, Kalamon, Amfissis, and Konservolia, fermented either by Greek style (in brine or salt-drying) or by Spanish style, in order to evaluate their microbial communities. Moreover, analytical methods were used to evaluate their biochemical properties. The prevailing bacterial species of all olives belonged to Lactobacillaceae, Leuconostocaceae, and Erwiniaceae families, while the most abundant yeasts were of the Pichiaceae family. Principal coordinates analysis showed a clustering of samples cured by salt-drying and of samples stored in brine, regardless of their cultivar. The biochemical evaluation of total phenol content, antioxidant activity, hydroxytyrosol, oleuropein, oleocanthal, and oleacein showed that salt-dried olives had low amounts of hydroxytyrosol, while Spanish-style green olives had the highest amounts of oleocanthal. All the other values exhibited various patterns, implying that more than one factor affects the biochemical identity of the final product. The protocols applied in this study can provide useful insights for the final product, both for the producers and the consumers.

The Use of Ozone Technology to Control Microorganism Growth, Enhance Food Safety and Extend Shelf Life: A Promising Food Decontamination Technology

The need for microorganism control in the food industry has promoted research in food processing technologies. Ozone is considered to be a promising food preserving technique and has gained great interest due to its strong oxidative properties and significant antimicrobial efficiency, and because its decomposition leaves no residues in foods. In this ozone technology review, the properties and the oxidation potential of ozone, and the intrinsic and extrinsic factors that affect the microorganism inactivation efficiency of both gaseous and aqueous ozone, are explained, as well as the mechanisms of ozone inactivation of foodborne pathogenic bacteria, fungi, mould, and biofilms. This review focuses on the latest scientific studies on the effects of ozone in controlling microorganism growth, maintaining food appearance and sensorial organoleptic qualities, assuring nutrient contents, enhancing the quality of food, and extending food shelf life, e.g., vegetables, fruits, meat, and grain products. The multifunctionality effects of ozone in food processing, in both gaseous and aqueous form, have promoted its use in the food industries to meet the increased consumer preference for a healthy diet and ready-to-eat products, although ozone may present undesirable effects on physicochemical characteristics on certain food products at high concentrations. The combined uses of ozone and other techniques (hurdle technology) have shown a promotive future in food processing. It can be concluded from this review that the application of ozone technology upon food requires increased research; specifically, the use of treatment conditions such as concentration and humidity for food and surface decontamination.

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.

Removal of Alternaria mycotoxins exposed to different food components by cold plasma

Alternariol (AOH) and alternariol monomethyl ether (AME), the two Alternaria mycotoxins with the highest outbreak rates in food systems, could be effectively reduced by cold plasma. This research evaluated the impact of food components on the plasma removal of AOH and AME. The results showed that 6% whey protein or ovalbumin almost completely inhibited the reduction of AOH or AME. Polyphenols inhibited the removal of AOH and AME by up to 90.8% and 83.4%, respectively. Organic acids and Vc reduced AME removal by up to 43.4% and 31.9%, respectively, but had little effect on AOH removal. Sugars and amino acids could decrease both toxin removal by less than 10%. Proteins exhibited the most inhibitory effect on plasma removal of AOH and AME, followed by polyphenols, while the effect of other components was relatively small. AOH and AME removal by cold plasma was highly related to H₂O₂ produced during plasma discharge.

Morphological and chemical characterization of Alternaria populations from apple fruit

Alternaria is a frequent contaminant of apple fruit, causing severe economic losses. It can produce external lesions and mouldy core, characterised by a rotten area in the apple core. In the present study, morphological and chemical characterization of Alternaria from apples was performed, evaluating differences related to agricultural practices and type of disease. A low morphological diversity was observed; most of the isolates were identified as A. tenuissima sp.-grp. (95 %). A. arborescens sp.-grp. and A. gaisen sp.-grp. were present in a proportion of 1 %, and 3 % of the isolates showed intermediate characteristics between these sp.-grps. and were identified as Alternaria sp. The chemical diversity was greater; 27 secondary metabolites were produced by the apple isolates. The most frequents were altertoxin-I (85 %), altechromone A (76 %), tentoxin (69 %), and tenuazonic acid (68 %). The alternariols were produced in a lower frequency when comparing with isolates from other crops; alternariol, 58 % and alternariol monomethyl ether, 57 %. The predominant secondary metabolite profile included compounds from different chemical families, such as dibenzopyrones, tetramic acids, perylene quinones, and cyclic tetrapeptides. A wider metabolomic capacity was observed in isolates from conventional apples when compared to those from organic fruit, with the predominance of strong producers of altertoxins and alternariols. The isolates from mouldy core showed higher ability to produce metabolites from different chemical families than those from external lesions. The wide chemical diversity of the Alternaria apple population should be considered to assess the health risk associated with apple by-products.

Characteristics of Fungal Communities and Internal Mildew Occurrence during the Stages of Planting and Storing of Sunflower Seed in China

Internally mildewed sunflower seeds pose a significant risk to human health. To control internal mildew, it is imperative to study its source in the main production area of China, which has been little investigated. Here, high-throughput sequencing was used to characterize the fungal and fungus-seed communities. Alpha diversity and ANOSIM analyses showed mildew did not alter the fungal compositions significantly. STAMP analysis showed that the sunflower seeds were most vulnerable to internal mildew during the field-planting stage. Alternaria was the predominant mildew-causing pathogen of sunflower seeds for consumption, which may originate from seed transmission and colonize at the seed-development stage. Finally, only a few seeds developed internal mildew with a worrisome level of Alternaria contamination in the humid field climate. NMDS analysis showed that climatic factors also played important roles in shaping microbial change during storage, with a relative humidity (RH) of 67% being the critical threshold in normal-temperature warehouses. Internal mildew never occurred below the RH threshold for the microbial community structure, which hardly changed after an average storage duration. The results indicated that a combination of field management to combat Alternaria, pretreatment with 5 KGy γ-irradiation and drying at the time of storage will minimize or prevent internal mildew. This work also provides an empirical framework for studies of mildewing in other shelled seeds.

Fungal Diversity in Barley Under Different Storage Conditions

The diversity of fungi in barley in simulated storage environments was analyzed. Barley was stored at different temperatures (15, 25, 35°C) and relative humidity (55, 65, 75, 85 RH) for 180 and 360 days. Alpha diversity, beta diversity, species composition, and species differences were analyzed using Illumina HiSeq technology. The fungal communities in all barley samples before and after storage belonged to 3 phyla, 18 classes, 39 orders, 71 families, 103 genera, and 152 species. The relative abundance of the dominant phylum Ascomycota was 77.98–99.19%. The relative abundance of Basidiomycota was 0.77–21.96%. At the genus level, the dominant genera of fungi in barley initially included Fusarium, Aspergillus, Microdochium, Alternaria, and Epicoccum. After 360 days of storage, the dominant genera became Epicoccum, Alternaria, Bipolar, Cladosporium, Fusarium, and Aspergillus. According to Venn diagrams and principal coordinates analysis, the fungal community diversity in barley initially was much higher than in barley stored at different temperatures and humidity. The application of PLS-DA could accurately distinguish between barley stored for 180 and 360 days. Some high-temperature and high-humidity environments accelerated storage. The dominant genera differed in different storage conditions and constantly changed with increasing storage duration. Epicoccum was one of the dominant genera after longer storage periods. This study provides theoretical support for optimizing safe storage conditions in barley.

Roles of AaVeA on Mycotoxin Production via Light in Alternaria alternata

Alternaria alternata is a principal plant pathogen responsible for the biosynthesis of mycotoxins, including tenuazonic acid (TeA), alternariol (AOH), and alternariol monomethyl ether (AME). The velvet gene VeA is involved in fungal growth, development, and secondary metabolism, including mycotoxin biosynthesis via light regulation. In this study, the detailed regulatory roles of AaVeA in A. alternata with various light sources were investigated from the comparative analyses between the wild type and the gene knockout strains. In fungal growth and conidiation, mycelial extension was independent of light regulation in A. alternata. Red light favored conidiation, but blue light repressed it. The absence of AaVeA caused the marked reduction of hyphae extension and conidiophore formation even though red light could not induce more spores in ΔAaVeA mutant. The differentially expressed genes (DEGs) enriched in hyphal growth and conidiation were drastically transcribed from the comparatively transcriptomic profile between the wild type and ΔAaVeA mutant strains with or without light. In mycotoxin production, TeA biosynthesis seems no obvious effect by light regulation, but AOH and AME formation was significantly stimulated by blue light. Nevertheless, the disruption of AaVeA resulted in a marked decrease in mycotoxin production and the action of the stimulation was lost via blue light for the abundant accumulation of AOH and AME in the ΔAaVeA strain. From DEG expression and further verification by RT-qPCR, the loss of AaVeA caused the discontinuous supply of the substrates for mycotoxin biosynthesis and the drastic decline of biosynthetic gene expression. In addition, pathogenicity depends on AaVeA regulation in tomato infected by A. alternata in vivo. These findings provide a distinct understanding of the roles of AaVeA in fungal growth, development, mycotoxin biosynthesis, and pathogenicity in response to various light sources.

Postharvest UV-C irradiation inhibits blackhead disease by inducing disease resistance and reducing mycotoxin production in 'Korla' fragrant pear (Pyrus sinkiangensis)

Blackhead disease is a major fungal disease causing the quality deterioration of postharvest 'Korla' fragrant pear. In this study, the relationships of resistance to blackhead disease with the enzyme activity, phenolic compounds, and mycotoxin metabolism of 'Korla' fragrant pear were investigated, through UV-C irradiation of 0.12, 0.24, 0.36, 0.48, 0.72 and 1.08 kJ/m² on 'Korla' fragrant pear inoculated with Alternaria alternata (Fries) Keissler (A. alternata). The results showed that the low-dose UV-C irradiation (0.36 kJ/m²) effectively controlled blackhead disease. The activities of chitinase (CHI), β-1,3-glucanase (GLU), peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), phenylalanine ammonia-lyase (PAL), and the content of phenolic compounds in fruit were enhanced, whereas the activities of lipoxygenase (LOX), polyphenol oxidase (PPO), and the contents of hydrogen peroxide (H₂O₂) and mycotoxins (including AOH, AME, and TeA) were decreased. Therefore, the low-dose UV-C irradiation could improve the resistance to blackhead disease and reduce the production of mycotoxins in 'Korla' fragrant pear. This study proves that UV-C irradiation may be a potentially effective strategy for the control of blackhead disease and the improvement of quality of postharvest 'Korla' fragrant pear.

Screening of multi-mycotoxins in fruits by ultra-performance liquid chromatography coupled to ion mobility quadrupole time-of-flight mass spectrometry

A modified quick, easy, cheap, effective, rugged, and safe extraction procedure combined with ultra-performance liquid chromatographic separation and ion mobility quadrupole time-of-flight mass spectrometry was developed to determine the presence of 20 mycotoxins (i.e., Alternaria toxins, ochratoxin, patulin, aflatoxin and trichothecenes) in fruit samples from Xinjiang. A complete platform, including screening via an in-house library, confirmation and quantification using reference standards, was established, which provided accurate MS data and complete spectra containing the fragment ions for each analyte. To evaluate the performance of the developed method, satisfactory validation parameters, such as linearity (R² ≥ 0.9992), precision (RSDs ≤ 9.8%), recovery (81.2-99.2%), LOD (0.06-2.22 µg kg^-1), and LOQ (0.2-7.39 µg kg^-1), were obtained. The analysis of 130 fruit samples revealed nonnegligible contamination with mycotoxins; specifically, the highest levels of three Alternaria toxins were detected in jujube, wolfberries and raisins.

Natural Occurrence of Alternaria Fungi and Associated Mycotoxins in Small-Grain Cereals from The Urals and West Siberia Regions of Russia

Alternaria fungi dominate the grain microbiota in many regions of the world; therefore, the detection of species that are able to produce mycotoxins has received much attention. A total of 178 grain samples of wheat, barley and oat obtained from the Urals and West Siberia regions of Russia in 2017–2019 were included in the study. Grain contamination with Alternaria fungi belonging to sections Alternaria and Infectoriae was analysed using qPCR with specific primers. The occurrence of four mycotoxins produced by Alternaria, AOH, AME, TEN, and TeA, was defined by HPLC-MS/MS. Alternaria DNA was found in all analysed grain samples. The prevalence of DNA of Alternaria sect. Alternaria fungi (range 53 × 10⁻⁴–21,731 × 10⁻⁴ pg/ng) over the DNA of Alternaria sect. Infectoriae (range 11 × 10⁻⁴‒4237 × 10⁻⁴ pg/ng) in the grain samples was revealed. Sixty-two percent of grain samples were contaminated by at least two Alternaria mycotoxins. The combination of TEN and TeA was found most often. Eight percent of grain samples were contaminated by all four mycotoxins, and only 3% of samples were free from the analysed secondary toxic metabolites. The amounts varied in a range of 2–53 µg/kg for AOH, 3–56 µg/kg for AME, 3–131 µg/kg for TEN and 9–15,000 µg/kg for TeA. To our knowledge, a new global maximum level of natural contamination of wheat grain with TeA was detected. A positive correlation between the amount of DNA from Alternaria sect. Alternaria and TeA was observed. The significant effects of cereal species and geographic origin of samples on the amounts of DNA and mycotoxins of Alternaria spp. in grain were revealed. Barley was the most heavily contaminated with fungi belonging to both sections. The content of AOH in oat grain was, on average, higher than that found in wheat and barley. The content of TEN in the grain of barley was lower than that in wheat and similar to that in oat. The content of TeA did not depend on the cereal crop. The effect of weather conditions (summer temperature and rainfall) on the final fungal and mycotoxin contamination of grain was discussed. The frequent co-occurrence of different Alternaria fungi and their mycotoxins in grain indicates the need for further studies investigating this issue.

Mycotoxin Profile and Phylogeny of Pathogenic Alternaria Species Isolated from Symptomatic Tomato Plants in Lebanon

The tomato is one of the most consumed agri-food products in Lebanon. Several fungal pathogens, including Alternaria species, can infect tomato plants during the whole growing cycle. Alternaria infections cause severe production and economic losses in field and during storage. In addition, Alternaria species represent a serious toxicological risk since they are able to produce a wide range of mycotoxins, associated with different toxic activities on human and animal health. Several Alternaria species were detected on tomatoes, among which the most important are A. solani, A. alternata, and A. arborescens. A set of 49 Alternaria strains isolated from leaves and stems of diseased tomato plants were characterised by using a polyphasic approach. All strains were included in the recently defined phylogenetic Alternaria section and grouped in three well-separated sub-clades, namely A. alternata (24 out of 49), A. arborescens (12 out of 49), and A. mali morpho-species (12 out of 49). One strain showed high genetic similarity with an A.limoniasperae reference strain. Chemical analyses showed that most of the Alternaria strains, cultured on rice, were able to produce alternariol (AOH), alternariol methyl ether (AME), altenuene (ALT) and tenuazonic acid (TA), with values up to 5634, 16,006, 5156, and 4507 mg kg⁻¹, respectively. In addition, 66% of the strains were able to co-produce simultaneously the four mycotoxins investigated. The pathogenicity test carried out on 10 Alternaria strains, representative of phylogenetic sub-clades, revealed that they were all pathogenic on tomato fruits. No significant difference among strains was observed, although A. alternata and A. arborescens strains were slightly more aggressive than A. mali morpho-species strains. This paper reports new insights on mycotoxin profiles, genetic variability, and pathogenicity of Alternaria species on tomatoes.

Enhanced Non-Toxic Immunodetection of Alternaria Mycotoxin Tenuazonic Acid Based on Ferritin-Displayed Anti-Idiotypic Nanobody-Nanoluciferase Multimers

The non-toxic immunoassay for mycotoxins is being paid more attention due to its advantages of higher safety and cost savings by using anti-idiotype antibodies to substitute toxins. In this study, with tenuazonic acid (TeA), a kind of highly toxic Alternaria mycotoxin as the target, an enhanced non-toxic immunoassay was developed based on the ferritin-displayed anti-idiotypic nanobody-nanoluciferase multimers. First, three specific β-type anti-idiotype nanobodies (AId-Nbs) bearing the internal image of TeA mycotoxin were selected from an immune phage display library. Then, the AId-Nb 2D with the best performance was exploited to generate a nanoluciferase (Nluc)-functionalized fusion monomer, by which a one-step non-toxic immunodetection format for TeA was established and proven to be effective. To further improve the affinity of the monomer, a ferritin display strategy was used to prepare 2D-Nluc fusion multimers. Finally, an enhanced bioluminescent enzyme immunoassay (BLEIA) was established in which the half maximal inhibitory concentration (IC₅₀) for TeA was 6.5 ng/mL with a 10.5-fold improvement of the 2D-based enzyme-linked immunosorbent assay (ELISA). The proposed assay exhibited high selectivities and good recoveries of 80.0-95.2%. The generated AId-Nb and ferritin-displayed AId-Nb-Nluc multimers were successfully extended to the application of TeA in food samples. This study brings a new strategy for production of multivalent AId-Nbs and non-toxic immunoassays for trace toxic contaminants.

Development of a chemiluminescence immunoassay for detection of tenuazonic acid mycotoxin in fruit juices with a specific camel polyclonal antibody

The natural mycotoxin tenuazonic acid (TeA) in foods is identified as the most toxic mycotoxin among the over 70 kinds of secondary toxic metabolites produced by Alternaria alternata. Some hapten-antibody-mediated immunoassays have been developed for TeA detection in food samples, but these methods show unsatisfactory sensitivity and specificity. In this study, a rationally designed hapten for TeA mycotoxin generated with computer-assisted modeling was prepared to produce a highly specific camel polyclonal antibody, and an indirect competitive chemiluminescence enzyme immunoassay (icCLEIA) was established with a limit of detection of 0.2 ng mL-1 under optimized conditions. The cross-reactivity results showed that several analogs and some common mycotoxins had negligible recognition by the anti-TeA polyclonal antibody. The average recoveries spiked in fruit juices were determined to be 92.7% with an acceptable coefficient of variation, and good correlations between icCLEIA and liquid chromatography tandem mass spectrometry (LC-MS/MS) results were obtained in spiked samples. This developed icCLEIA for TeA detection with significantly improved sensitivity and satisfactory specificity is a promising alternative for environmental monitoring and food safety.

Characterization of Alternaria Species Associated with Heart Rot of Pomegranate Fruit

This study was aimed at identifying Alternaria species associated with heart rot disease of pomegranate fruit in southern Italy and characterizing their mycotoxigenic profile. A total of 42 Alternaria isolates were characterized. They were obtained from pomegranate fruits with symptoms of heart rot sampled in Apulia and Sicily and grouped into six distinct morphotypes based on macro- and microscopic features. According to multigene phylogenetic analysis, including internal transcribed spacer (ITS), translation elongation factor 1-α (EF-1α), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and a SCAR marker (OPA10-2), 38 isolates of morphotypes 1 to 5 were identified as Alternaria alternata, while isolates of morphotype 6, all from Sicily, clustered within the Alternaria arborescens species complex. In particular, isolates of morphotype 1, the most numerous, clustered with the ex-type isolate of A. alternata, proving to belong to A. alternata. No difference in pathogenicity on pomegranate fruits was found between isolates of A. alternata and A. arborescens and among A. alternata isolates of different morphotypes. The toxigenic profile of isolates varied greatly: in vitro, all 42 isolates produced tenuazonic acid and most of them other mycotoxins, including alternariol, alternariol monomethyl ether, altenuene and tentoxin.

Nanostructured chitosan edible coating loaded with α-pinene for the preservation of the postharvest quality of Capsicum annuum L. and Alternaria alternata control

Bell peppers are susceptible to postharvest diseases caused by the fungus Alternaria alternata that limit its commercialization. Nowadays, nanotechnology allows encapsulation of natural components such as terpenes. The objective of this work was to develop chitosan nanoparticles with α-pinene (P-CSNPs) and a nanostructured edible coating (EC-P-CSNPs). The P-CSNPs were characterized by TEM (Transmission Electron Microscopy), FTIR (Fourier-Transform Infrared Spectroscopy), DLS (Dynamic Light Scattering) and ζ potential. The P-CSNPs and the EC-P-CSNPs were applied to the bell peppers inoculated with A. alternata under cold storage for either 0, 7, 14 and 21 days at 12 ± 2 °C followed by a shelf-life period of 5 days at 20 ± 2 °C to assess their post-harvest quality. Nanoparticles size was 3.9 ± 0.5 nm and the ζ potential value was between 13.4 and 14.9 mV. The incorporation of α-pinene was corroborated by FTIR. Significant changes in weight loss were obtained for P-CSNPs and EC-P-CSNPs at percentage of 3 and 6% compared to the control. For firmness, color, total soluble solids, titratable acids, maturity index, total flavonoid content and antioxidant capacity, no differences were found. Total carotenes were higher in bell peppers without A. alternata. The chitosan nanoparticles and edible coating inhibited A. alternata during the cold storage period of bell pepper and preserved the physicochemical quality.

Genetic diversity of Alternaria species associated with black point in wheat grains

The genus Alternaria is a widely distributed major plant pathogen that can act as a saprophyte in plant debris. Fungi of this genus frequently infect cereal crops and cause such diseases as black point and wheat leaf blight, which decrease the yield and quality of cereal products. A total of 25 Alternaria sp. isolates were collected from germ grains of various wheat cultivars from different geographic regions in Kazakhstan. We investigated the genetic relationships of the main Alternaria species related to black point disease of wheat in Kazakhstan, using the inter-primer binding site (iPBS) DNA profiling technique. We used 25 retrotransposon-based iPBS primers to identify the differences among and within Alternaria species populations, and analyzed the variation using clustering (UPGMA) and statistical approaches (AMOVA). Isolates of Alternaria species clustered into two main genetic groups, with species of A.alternata and A.tennuissima forming one cluster, and isolates of A. infectoria forming another. The genetic diversity found using retrotransposon profiles was strongly correlated with geographic data. Overall, the iPBS fingerprinting technique is highly informative and useful for the evaluation of genetic diversity and relationships of Alternaria species.

Microbiological and Nutritional Analysis of Lettuce Crops Grown on the International Space Station

The ability to grow safe, fresh food to supplement packaged foods of astronauts in space has been an important goal for NASA. Food crops grown in space experience different environmental conditions than plants grown on Earth (e.g., reduced gravity, elevated radiation levels). To study the effects of space conditions, red romaine lettuce, Lactuca sativa cv 'Outredgeous,' plants were grown in Veggie plant growth chambers on the International Space Station (ISS) and compared with ground-grown plants. Multiple plantings were grown on ISS and harvested using either a single, final harvest, or sequential harvests in which several mature leaves were removed from the plants at weekly intervals. Ground controls were grown simultaneously with a 24-72 h delay using ISS environmental data. Food safety of the plants was determined by heterotrophic plate counts for bacteria and fungi, as well as isolate identification using samples taken from the leaves and roots. Molecular characterization was conducted using Next Generation Sequencing (NGS) to provide taxonomic composition and phylogenetic structure of the community. Leaves were also analyzed for elemental composition, as well as levels of phenolics, anthocyanins, and Oxygen Radical Absorbance Capacity (ORAC). Comparison of flight and ground tissues showed some differences in total counts for bacteria and yeast/molds (2.14 - 4.86 log10 CFU/g), while screening for select human pathogens yielded negative results. Bacterial and fungal isolate identification and community characterization indicated variation in the diversity of genera between leaf and root tissue with diversity being higher in root tissue, and included differences in the dominant genera. The only difference between ground and flight experiments was seen in the third experiment, VEG-03A, with significant differences in the genera from leaf tissue. Flight and ground tissue showed differences in Fe, K, Na, P, S, and Zn content and total phenolic levels, but no differences in anthocyanin and ORAC levels. This study indicated that leafy vegetable crops can produce safe, edible, fresh food to supplement to the astronauts' diet, and provide baseline data for continual operation of the Veggie plant growth units on ISS.

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

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

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.

Understanding the effect of postharvest tomato temperatures on two toxigenic Alternaria spp. strains: growth, mycotoxins and cell-wall integrity-related gene expression

BACKGROUND

Tomato fruit is susceptible to Alternaria spp. spoilage. Correct postharvest management is necessary to prevent mold growth and mycotoxin accumulation, temperature being one of the main factors associated with these problems. The effect of different postharvest temperatures (5, 12, 25, and 35 °C) on growth, mycotoxin production, and stress-related gene expression by two Alternaria spp. was assessed.

RESULTS

Growth rates decreased rapidly when temperature was higher than the optimum (25 °C), while a gradual reduction was detected at lower temperatures. Tenuazonic acid (TeA) was strongly synthesized at all the temperatures that were evaluated, with a maximum between 12 and 25 °C. Alternariol monomethyl ether (AME) was produced only at the two lowest temperatures, with a peak at 12 °C. Regarding the expression of the stress-related RHO1 gene, during active fungal growth both Alternaria spp. showed more copies of the gene as temperature increased. At the stationary phase, RHO1 gene expression was significantly higher at 12 °C, coinciding with the highest accumulation of AME.

CONCLUSION

Changes in temperature related to different postharvest stages of tomato fruits markedly affect toxigenic Alternaria spp. The highest levels of both mycotoxins were recorded at 12 °C, a common storage temperature for tomato fruit. An association between alternariol biosynthesis and the cell wall integrity pathway was also noticed in relation to temperature, suggesting that temperature may act as a stressor stimulating the RHO1 gene expression, which in turn triggers this mycotoxin synthesis. These results will be useful in developing new strategies to control Alternaria spoilage efficiently in tomato fruit and by-products. © 2019 Society of Chemical Industry.

Interactions of Mycotoxin Alternariol with Cyclodextrins and its Removal from Aqueous Solution by Beta-Cyclodextrin Bead Polymer

Alternariol is an Alternaria mycotoxin that appears in fruits, tomatoes, oilseeds, and corresponding products. Chronic exposure to it can induce carcinogenic and xenoestrogenic effects. Cyclodextrins (CDs) are ring-shaped molecules built up by glucose units, which form host–guest type complexes with some mycotoxins. Furthermore, insoluble CD polymers seem suitable for the extraction/removal of mycotoxins from aqueous solutions. In this study, the interactions of alternariol with β- and γ-CDs were tested by employing fluorescence spectroscopic and modeling studies. Moreover, the removal of alternariol from aqueous solutions by insoluble β-CD bead polymer (BBP) was examined. Our major observations/conclusions are the following: (1) CDs strongly increased the fluorescence of alternariol, the strongest enhancement was induced by the native γ-CD at pH 7.4. (2) Alternariol formed the most stable complexes with the native γ-CD (logK = 3.2) and the quaternary ammonium derivatives (logK = 3.4–3.6) at acidic/physiological pH and at pH 10.0, respectively. (3) BBP effectively removed alternariol from aqueous solution. (4) The alternariol-binding ability of β-CD polymers was significantly higher than was expected based on their β-CD content. (5) CD technology seems a promising tool to improve the fluorescence detection of alternariol and/or to develop new mycotoxin binders to decrease alternariol exposure.

Alternaria SPP. in food commodities of Slovak origin: occurrence and mycotoxin production abilities

Various food commodities of Slovak origin were analysed for the occurrence of Alternaria species-groups. Totally we analysed 14 samples of grapes, 3 samples of barley, 2 samples of wheat, 17 samples of fruit, vegetable and fruit-vegetable juices, 6 samples of red kuri squash with macroscopically visible infection. Mycological analyses were performed by using plate dilution method, method of direct placing of berries or grains on the plates with dichloran, rose bengal and chloramphenicol agar or by direct inoculation by mycological needle to the identification medium (potato-carrot agar). In all grape, barley, wheat and squash samples the presence of representatives of this genus was detected (100% isolation frequency). In juices, 41% of the samples were positive for their occurrence. The highest relative density of Alternaria isolates was found in grape samples (87%). All detected strains were segregated into four morphological species-groups: A. alternata, A. arborescens, A. infectoria and A. tenuissima. The most dominant species-group in grapes was A. arborescens, in barley and wheat A. tenuissima, followed by A. alternata, in juices only A. alternata and A. arborescens species-groups were detected and isolates of squashes were not classified to the species-groups. Randomly selected 67 isolates were analysed for the ability to produce mycotoxins alternariol (AOH), alternariol monomethylether (AME) and altenuene (ALT) by means of thin-layer chromatography. Of all tested isolates, AOH production was most frequently reported (70% of tested isolates). AME was produced by 60% and ALT by 49% of tested isolates. The largest share of the productive strains originated from the squashes, where all tested isolates produced ALT and AOH, followed by isolates of juices. From the viewpoint of individual species-groups, A. arborescens isolates and Alternaria spp. appeared to be the most productive in all mycotoxins tested.

A new high-resolution melting assay for genotyping Alternaria species causing citrus brown spot

BACKGROUND

Alternaria brown spot is one of the most important diseases of tangerines and their hybrids worldwide. To set up effective control strategy, the accurate detection and identification of the species responsible for the diseases is crucial. However, characterization based on morphology and/or multilocus genetic approaches is time consuming, requires great expertise and sometimes is not conclusive. Therefore, the set-up of a rapid and efficient DNA-based assay might be of paramount importance. High-resolution melting (HRM) analysis represents an interesting tool for the uncovering of nucleotide variations as small as one base difference and, as such, relevant to species characterization.

RESULTS

In the present investigation, an HRM assay based on the Alternaria barcoding region OPA1-3 was set up. Specimen strains of the main citrus-associated Alternaria species and morphotypes generated distinct and normalized profiles, allowing their differentiation when HRM-tested. Moreover, when the assay was used to screen an Alternaria collection from citrus fruit and leaves, it distributed the 180 isolates in three independent clusters, readily and consistently resolved. Isolates were identified as belonging to the species Alternaria alternata and the species complex A. arborescens. Within A. alternata, the morphotypes alternata (77% of the collection) and limoniasperae (17% of the collection) were present.

CONCLUSIONS

Although further validation experiments will be performed to optimize the assay for a diagnostic use, this HRM approach might represent a rapid, sensitive and specific method for the detection and identification of Alternaria spp. responsible for citrus brown spot disease. © 2018 Society of Chemical Industry.

Chemotaxonomy of Mycotoxigenic Small-Spored Alternaria Fungi - Do Multitoxin Mixtures Act as an Indicator for Species Differentiation?

Necrotrophic as well as saprophytic small-spored Alternaria (A.) species are annually responsible for major losses of agricultural products, such as cereal crops, associated with the contamination of food and feedstuff with potential health-endangering Alternaria toxins. Knowledge of the metabolic capabilities of different species-groups to form mycotoxins is of importance for a reliable risk assessment. 93 Alternaria strains belonging to the four species groups Alternaria tenuissima, A. arborescens, A. alternata, and A. infectoria were isolated from winter wheat kernels harvested from fields in Germany and Russia and incubated under equal conditions. Chemical analysis by means of an HPLC-MS/MS multi-Alternaria-toxin-method showed that 95% of all strains were able to form at least one of the targeted 17 non-host specific Alternaria toxins. Simultaneous production of up to 15 (modified) Alternaria toxins by members of the A. tenuissima, A. arborescens, A. alternata species-groups and up to seven toxins by A. infectoria strains was demonstrated. Overall tenuazonic acid was the most extensively formed mycotoxin followed by alternariol and alternariol mono methylether, whereas altertoxin I was the most frequently detected toxin. Sulfoconjugated modifications of alternariol, alternariol mono methylether, altenuisol and altenuene were frequently determined. Unknown perylene quinone derivatives were additionally detected. Strains of the species-group A. infectoria could be segregated from strains of the other three species-groups due to significantly lower toxin levels and the specific production of infectopyrone. Apart from infectopyrone, alterperylenol was also frequently produced by 95% of the A. infectoria strains. Neither by the concentration nor by the composition of the targeted Alternaria toxins a differentiation between the species-groups A. alternata, A. tenuissima and A. arborescens was possible.

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.