Archivio Journal of Plant Pathology

Abstract:

During summer-autumn 2014, extensive necroses were observed on Salvia leucantha plants growing in a private garden near Biella (northern Italy, ca 45°39’N 8°00’E). A high proportion (70%) of about 100 plants was diseased. Pale-brown, small, irregular lesions were present on the leaves, which were followed by extensive chlorosis and, eventually, leaf drop. A fungus was consistently isolated on potato dextrose agar (PDA) which on potato carrot agar (PCA), produced a greenish mycelium, with brown, septate, ovoid or obclavate conidia with both transverse and longitudinal septa and a prominent tapered beak, measuring 14.3- 42.3×5.4-12.6 μm (average: 22.8×9.1 μm). These morphometric traits were consistent with those of Alternaria sp. (Simmons, 2007). DNA was extracted using the Nucleospin plant kit (Macherey Nagel, Germany) and PCR carried out using ITS1/ITS4 primers. A 483 bp PCR product was amplified and sequenced (GenBank accession No KP280314) and a BLASTn search (Altschul et al., 1997) confirmed that the sequence corresponded to Alternaria sp. In pathogenicity tests, leaves of three healthy plants of S. leucantha were inoculated by spraying with a spore and mycelium suspension (1×105 CFU/ml) of the fungus grown on PDA. Plants inoculated only with sterile PDA fragments suspended in water served as control. Inoculated plants were covered with plastic bags and maintained at 18 to 25°C. At about six days post inoculation lesions developed only on inoculated leaves and Alternaria sp. was consistently reisolated. This is the first report of Alternaria sp. on S. leucantha in Italy as well as in the world.