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Members of the Fusarium graminearum species complex (FGSC), such as F. graminearum and F. asiaticum, are the main cause of fusarium head blight (FHB) of wheat and barley worldwide. In this study, 117 FGSC isolates obtained from commercial barley grain produced in Argentina (n = 43 isolates), Brazil (n = 35), and Uruguay (n = 39) were identified to species and trichothecene genotypes, and analysed using amplified fragment length polymorphism (AFLP) and sequence‐related amplified polymorphism (SRAP) markers. In addition, reductase (RED) and trichothecene 3‐O‐acetyltransferase (Tri101) were sequenced for a subset of 24 isolates. The majority of the isolates (n = 103) were identified as F. graminearum, which was the only species found in Argentina. In Uruguay, only one F. cortaderiae isolate was found among F. graminearum isolates. In Brazil, F. graminearum also dominated the collection (22/35), followed by F. meridionale (8/35), F. asiaticum (2/35), F. cortaderiae (2/35) and F. austroamericanum (1/35). Species were structured by trichothecene genotype: all F. graminearum were of the 15‐acetyldeoxynivalenol (ADON), F. meridionale, F. asiaticum and F. cortaderiae were of the nivalenol (NIV), and F. austroamericanum was of the 3‐ADON genotype. Both AFLP and SRAP data showed high levels of genetic variability, which was higher within than among countries. Isolates were not structured by country of origin. SRAP analysis grouped F. graminearum in a separate cluster from the other species within the complex. However, AFLP analysis failed to resolve the species into distinct clades with partial clustering of F. meridionale, F. austroamericanum, F. asiaticum and F. graminearum isolates.

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 g kg −1 ) compared with other studies, followed by TeA (37%, 1522 g kg −1 ), while AME was present in five samples in the 2015 growing season only, with a mean of 4876 g 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.

One of the most important diseases in cereal crops is Fusarium head blight, being Fusarium graminearum the main etiological agent. This fungus has the ability to produce a wide spectrum and quantity of toxins, especially deoxynivalenol (DON). During the last crop season (2012-2013) the climatic conditions favored Fusarium colonization. The objective of this work was to determine the presence of this fungus as well as the DON content in 50 wheat grain samples. Our results showed that 80% of the samples were contaminated with Fusarium graminearum. Twenty four percent (24%) of the samples contained ≥ 1μg/g DON, 26% ranged from 0,5 and 0,99μg/g, and the remaining 50% had values lower than 0,5μg/g. Correlation was found between the presence of Fusarium graminearum and DON. It is necessary to establish DON limit values in wheat grains for human consumption.

Fusarium poae is one of the Fusarium species isolated from grains associated with Fusarium head blight (FHB), whose occurrence has increased in the last years. In this study, a total of 105 F. poae isolates from Argentina,

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Wheat (Triticum aestivum L.), the most widely grown winter cereal crop in Argentina, is grown on 5 million ha. Fusarium species affect yield and grain quality because of mycotoxins. In December 2009, a screen of fungal species in wheat seeds from a field in Azul, Buenos Aires, Argentina was conducted. Four hundred seeds were surface sterilized by dipping successively into 70% ethanol for 2 min, 5% sodium hypochlorite for 2 min, and finally rinsing twice in fresh sterilized distilled water. The seeds were plated on potato dextrose agar (PDA), pH 6, and incubated at 24 ± 2°C with exposure to 12-h alternate cycles of darkness and light. Eight isolates morphologically similar to Fusarium species were observed after 6 days of incubation. For identification, monosporic isolates were transferred onto PDA and carnation leaf agar (CLA) to grow at the conditions described above (1). One isolate, when grown on PDA, rapidly produced abundant, dense, white, aerial mycelium that became pink with age and formed red pigments in the medium. On CLA, macroconidia were abundant, relatively slender, curved to lunate, and three to five septate. Microconidia were abundant, napiform, oval or pyriform, zero to one septate, and commonly clustered in false heads. Chlamydospores were absent. The fungus was identified as Fusarium tricinctum (Corda) Saccardo on the basis of fungal morphology (1). To complete Koch's postulates, the pathogenicity of the fungus was tested by spraying five healthy inflorescences (on average 16 spikelets per spike) of wheat with a 5-ml suspension (2 × 105 conidia per ml). Another two healthy inflorescences were sprayed with sterile distilled water. Plants were placed in a growth chamber with a 12-h photoperiod at 22 ± 2°C, covered with polyethylene bags that were removed after 3 days, and then moved to a glasshouse. The same procedure was repeated. While control inflorescences were asymptomatic, inoculated inflorescences showed a mean of five bleached spikelets per spike. By using the methodology described above, the fungus was reisolated from all infected grains of inoculated plants but not from the controls. To confirm the morphological diagnosis, the genomic DNA of the isolate was extracted (3) and the internal transcribed spacer (ITS) and the translation elongation factor (TEF) regions were PCR-amplified using primer pairs ITS3/ITS4 (4) and EF-1/EF-2 (2), respectively. The sequences were compared with those in GenBank. The ITS sequence (Accession No. HM635739) showed 100% similarity with several F. tricinctum sequences (e.g., Accession Nos. HM068317, FN598932, and EF589873) but also with other Fusarium species such as F. acuminatum. The TEF sequence (Accession No. HQ214681) showed 99 to 100% similarity with Accession Nos. HM068307, EU744838, and EU744837 of F. tricinctum. To our knowledge, this is the first report of F. tricinctum on wheat in Argentina. This species is known to produce fusarin C, enniatins, and moniliformin toxins. Since F. tricinctum can infect different cereal grains, a large-scale survey of cereals from fields throughout Argentina is in progress. References: (1) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Oxford, UK. 2006. (2) K. O'Donell et al. Proc. Nat. Acad. Sci. USA 95:2044, 1998. (3) S. A. Stenglein and P. A. Balatti. Physiol. Mol. Plant Pathol. 68:158, 2006. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

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