Fusarium proliferatum, a new pathogen on oat in Argentina

S.A. STENGLEIN; M.I. DINOLFO; M.V. MORENO; R. GALIZIO; G.L. SALERNO

PLANT DISEASE

AMER PHYTOPATHOLOGICAL SOC

Año: 2010 vol. 94 p. 783 - 784

0191-2917

In December 2008, a study of oat (cv. Graciela INTA) seeds from Trenque Lauquen, Buenos Aires, Argentina, was conducted. Seeds were surface sterilized by dipping successively into 70% ethanol for 2 minutes, 5% sodium hypochlorite for 2 minutes, rinsed twice in fresh sterilized distilled water, plated on 2% potato dextrose agar (PDA; pH 6) and incubated at 24±2°C with 12 h photoperiods. Six isolates morphologically similar to Fusarium spp. were observed after 6 days of incubation. For identification, monosporic isolates were transferred onto 2% PDA and carnation leaf agar (CLA) to grow with the conditions described above. Two isolates produced abundant, white, aerial mycelium and violet-to-dark (with age) pigments in the PDA. On CLA, macroconidia were abundant, slender, almost straight, thin walled and usually 3-5 septate. Microconidia were abundant, usually single celled, oval or club-shaped in chains (less commonly in false heads) on monophialides and polyphialides. Chlamydospores were absent. The fungus was identified as F. proliferatum based on fungal morphology. The pathogenicity of the fungus was tested by spraying 5 healthy inflorescences of oat with a 5 ml suspension (2 × 105 conidia/ml). Another 2 healthy inflorescences were sprayed with sterile distilled water. Plants were placed in a growth chamber with a 12 h photoperiod at 22±2°C and covered with polyethylene bags that were removed after 3 days and plants were moved to a glasshouse. Inoculated inflorescences showed bleaching glumes that sometimes became necrotic with some grains that presented pale brown discoloration and necrotic areas. The fungus was reisolated from glumes and grains of inoculated plants and not from controls. To confirm the morphological diagnosis, the genomic DNA of the isolates was extracted and a PCR reaction with specific primers was chosen. Successful amplifications were confirmed by gel electrophoresis. The size of the DNA fragment was estimated using a 100 bp DNA ladder. The expected size product (585 bp) was obtained, confirming the identification. This is thought to be the first report of F. proliferatum on oat in Argentina.