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First Report of Sclerotinia Blight Caused by Sclerotinia sclerotiorum on Fan Columbine (Aquilegia flabellata) in Italy

Fan columbine is a perennial garden species belonging to the family Ranunculaceae. During the spring of 2011, extensive wilting was observed on 5-month-old potted plants of Aquilegia flabellata grown in an experimental glasshouse belonging to the Center AGROINNOVA at Grugliasco (northern Italy). First symptoms included stem necrosis and darkening and withering of leaves. Plant wilt occurred a few days after the appearance of the first symptoms. Infected plants were characterized by the presence of soft, watery tissues. In the presence of high relative humidity, lesions became covered with a whitish mycelium and irregular, dark gray sclerotia (1.5 to 4.0 × 1.0 to 2.8, average 2.8 × 2.1 mm) were produced on the mycelium. Diseased tissue was surface sterilized for 1 min in 1% NaOCl and plated on potato dextrose agar (PDA) amended with 100 mg/l of streptomycin sulfate. Sclerotinia sclerotiorum (Lib.) de Bary (2) was consistently recovered from infected stem pieces. Sclerotia produced on PDA measured 2.0 to 7.0 × 2.0 to 5.0 (average 4.2 × 2.9) mm. The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1F/ITS4 and sequenced. BLAST analysis (1) of the 575-bp segment showed a 100% homology with the sequence of S. sclerotiorum (EF091809). The nucleotide sequence has been assigned the GenBank Accession No. JN013184. Pathogenicity of one isolate obtained from sclerotia of infected plants was confirmed by inoculating three 6-month-old plants transplanted in 16-cm-diameter pots in a glasshouse in a sphagnum peat/pomix/pine bark/clay (50:20:20:10) mix. Inoculum that consisted of 3 g/l of substrate of sterile wheat kernels infested with mycelium and sclerotia was placed in the soil and around the base of each plant. Three noninoculated plants served as controls. Plants were maintained in a growth chamber at 21 ± 1°C and relative humidity >90%. The inoculation trial was carried out twice. All inoculated plants developed leaf yellowing within 15 days of soil infestation. White, cottony mycelium and dark sclerotia developed on stems and at the base of all inoculated plants. Eventually, infected plants wilted. Control plants remained symptomless. S. sclerotiorum was reisolated from the stems of inoculated plants. To our knowledge, this is the first report of S. sclerotiorum on A. flabellata in Italy. The disease has been previously reported on A. vulgaris in the United States (3) and A. glandulosa in Russia (4). The economic importance of this disease in Italy is currently limited.

References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) N. F. Buchwald. Kgl. Veterisk Landb. Aarssk. 75, 1949. (3) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrived from http://nt.ars-grin.gov/fungaldatabases/, July 7, 2011. (4) P. M. Zhiboedov et al. Mikol. Fitopatol, 36:48, 2002.