FIRST REPORT OF LAUREL ANTHRACNOSE CAUSES BY COLLETOTRICHUM ACUTATUM IN CENTRAL ITALY

Abstract

Laurus nobilis (laurel) is an evergreen tree whose communities are spread throughout Italy (Filibeck, 2006). During summer 2014, in a laurel hedge of a garden near Rome symptoms were seen consisting of shoots with tips with typical 'shepherd’s crook' and necrotic spots on leaves and twigs. Tissue fragments from the margin of necrotic spots were cut, surface-disinfected (1% NaClO for 1 min), plated onto potato dextrose agar (PDA) and incubated at 25°C in the dark. A single fungal species was consistently isolated, pure cultures of which were obtained by single conidia transfer. The fungus was morphologically identified as Colletotrichum acutatum. DNA of one monosporic isolate (2002ER) was extracted and amplified with primers specific for the internal transcribed spacer (ITS) regions and the beta-tubulin gene (TUB2). This isolate showed 100% similarity with several C. acutatum strains (i.e. AJ301964, AJ301950, DQ286130) for the ITS region and C. acutatum strains (i.e. JQ424939, JN121284) for the TUB2 gene. Our sequences were deposited in European Nucleotide Archive (ENA) with the accession No. LN836025 for ITS, and No. LN836026 for TUB2. Mycelial plugs (5 mm diameter) cut from the margins of actively growing cultures were inserted under the epidermis at different levels of six-year-old potted laurel plants. Controls were inoculated with sterile PDA plugs. After 45 days inoculated plants grown at 24±2°C showed symptoms similar to those observed in the garden and C. acutatum was re-isolated from the margin of the lesions. There are a few report of anthracnose by other Colletotrichum species on laurel in Europe (Constantinescu and Jonsson, 1987; Gore and Bucak, 2006). To our knowledge, this is the first report of damages caused to laurel in Italy by C. acutatum.