Archivio Journal of Plant Pathology

Abstract:

Digitalis purpurea (family Scrophulariaceae), is a biennial species used in low maintenance gardens. In summer and autumn 2011 and 2012, in a private garden near Biella (northern Italy), a downy mildew was observed on the leaves of D. purpurea plants. Veindelimited chlorotic areas 4-20 mm2 in size coalesced and turned necrotic. Sporulation occurred primarily on the abaxial leaf surface. Conidiophores measuring 294-453×7-10 μm (average: 372×8 μm), branched dichotomously at the first branch and were followed by branches measuring 149-192 (average: 167) μm. Curved tips measured 10-18 μm (average: 14 μm). Conidia, ellipsoid to ovoid, measured 18-29×17-21 μm (average: 25×19 μm). The fungus was identified as Peronospora digitalidis (Hall, 1994). The DNA region encoding the large ribosomal subunit (LSU rDNA) was amplified using primers NL1/NL4 (Maier et al., 2003) and sequenced (GenBank accession No. KC461924). Symptoms were reproduced on five healthy D. purpurea plants inoculated with conidia from affected plants and maintained at high RH and temperatures from 18 to 25°C. P. digitalidis infections to D. purpurea have been recorded the USA (Tjosvold and Koike, 2002), New Zealand and many European countries (Hall, 1994). This is the first report in Italy.