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Occurrence of Fusarium solani on Blueberry in Argentina

Blueberry plants with root rot and sudden death symptoms were collected in Concordia, Entre Ríos. Diseased roots were disinfected by immersion in 0.5% NaOCl for 2 min, cut into pieces, transferred to carrot agar (CA), and maintained at 20 ± 2°C and 12 h of near UV light (Philips Black Light lamps TL 40W/08). Conidia were identified with an Olympus BX-51 optical microscope by using a CoolSNAP Pro digital kit with image-pro plus and color digital camera (Media Cybernetics, Inc., Silver Spring, MD). Macroconidia length was variable, 3.9 μm and as much as 29 μm (1 to 5 septa), and microconidia measured 3.8 × 11 μm. Fungal description agrees with Fusarium solani (1). Pathogenicity of the purified isolate was evaluated on 2-month-old plants (cvs. Misty and Sharp Blue). The purified, grayish white isolate was grown on CA for 7 days, and mycelial plugs were placed next to the base of wounded stem and roots immediately below the potting mix soil line. Plants were maintained in the dark at 20 ± 2°C and 90% humidity for 48 h, and then transferred to 12 h of light. Wounded plants with CA plugs served as controls. Dark spots along the stem and root and stem rot appeared 7 to 21 days after inoculation. Controls remained symptomless. The fungus was reisolated from inoculated plants. Fusarium sp. was previously cited (2). To our knowledge, this is the first report of F. solani on blueberry in Argentina.

References: (1) C. Booth. Fusarium. Laboratory Guide to the Identification of the Major Species. CMI, Kew, England, 1977. (2) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989.