CONICET | Buscador de Institutos y Recursos Humanos

Barley (Hordeum vulgare L.) is one of the most widely grown winter cereal crops in Argentina, and is primarily grown for use as malted barley for the beer industry. In December 2011, a survey of fungi in a barley (cv. Shakira) seed lot from a field located at Treinta de Agosto, Buenos Aires, Argentina, was conducted . A sample of four-hundred seeds was surface sterilized (70% EtOH for 2 min; 5% NaClO for 2 min), rinsed twice in sterilized distilled water, plated on potato dextrose agar (PDA), and incubated at 24 ± 2°C in a 12-h dark/light cycle. Ten isolates morphologically similar to Fusarium species were observed after 6 days incubation. For identification, monosporic isolates were transferred onto PDA and carnation leaf agar (CLA) to grow at the conditions described above. One isolate, when grown on PDA, produced abundant white aerial mycelium and formed red pigments in the medium. On CLA, macroconidia were abundant, falcate with the dorsal side more curved than the ventral, commonly 5 septate. Microconidia were not observed. Chlamydospores were observed after four weeks. The fungus was identified as F. cerealis (Cooke) Sacc. (synonym F. crookwellense Burgess, Nelson & Toussoun) on the basis of morphology (1). To complete Koch´s postulates, pathogenicity was conducted using a hand sprayer to inoculate ten barley (cv. Shakira ) heads in potted plants with a 5- ml spore suspension (1 × 104 conidia/ per ml). Four heads were sprayed with sterile distilled water as a control. Plants were covered with polyethylene bags and incubated for three days in a growth chamber under a 12- h day/dark cycle at 22 ± 2°C. Plants were unbagged and moved into a greenhouse. Non-inoculated spikelets were asymptomatic and inoculated spikelets showed discoloration or a tan to dark brown necrosis. The fungus was re-isolated from symptomatic kernels. DNA of the monosporic fungus re-isolated was extracted (2) and identified to species by sequencing the reductase (RED), trichothecene 3-O-acetyltransferase (tri101) and translation elongation factor (TEF) regions (3). The sequences were compared with those in GenBank. The RED sequence (Accesion No. JX682529), the tri101 (Accesion No. JX682530), and the TEF (Accesion No. JX682531) showed 100% similarity, with several F. cerealis sequences. Additionally, the isolate was tested for the potential to produce nivalenol (NIV) using a PCR approach (4). A PCR product indicative of a NIV genotype was obtained. To our knowledge, this is the first report of F. cerealis associated with barley kernels in Argentina. Considering its potential to cause head blight and product mycotoxins, a large-scale survey of F. cerealis on barley crops in Argentina is underway.

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