FIRST REPORT OF SCLEROTINIA SCLEROTIORUM ON BUTTERFLY LAVENDER IN ITALY
A. Garibaldi, D. Bertetti, S. Franco Ortega, M.L. Gullino
In the autumn of 2014, in a commercial farm at Albenga (northern Italy), a new disease was observed on 5-month-old potted plants of butterfly lavander (Lavandula stoechas). Initial symptoms consisted of stem necrosis, darkening and withering of the leaves followed by wiltinig of the plants. In the presence of high relative humidity, the lesions became covered with a whitish mycelium which produced irregular dark grey sclerotia 2.0-7.5×1.5-4.0 mm in size. From infected stem pieces placed on potato dextrose agar (PDA) whitish fungal colonies developed, which produced sclerotia measuring 0.6-3.0×0.6-2.7 mm. The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4 and sequenced (GenBank accession No. KP792750). BLAST analysis (Altschul et al., 1997) of the 492 bp amplified sequence showed a 99% homology with the sequence of Sclerotinia sclerotiorum (JX442064). The pathogenicity of one fungal isolate was tested by placing mycelium and sclerotia grown on autoclaved wheat kernels at the base of three healthy plants of L. stoechas. Control plants were inoculated with autoclaved wheat kernels alone. All the plants were covered with plastic bags and maintained at 25±1°C. First symptoms, consisting of stem necrosis and leaf withering, appeared on inoculated plants five days post inoculation Whereas S. sclerotiorum was constantly reisolated from symptomatic plants, controls remained symptomless. To the best of our knowledge, this is the first report of S. sclerotiorum on L. stoechas in Italy as well as worldwide.