Archivio Journal of Plant Pathology

Abstract:

In summer 2012, a blight was observed on leaves and stems of several 90-day-old plants of Lavandula officinalis grown in a farm located near Albenga (northern Italy). Semi-circular, water soaked lesions appeared on the leaves, starting from the basal ones. Rhizoctonia solani was consistently isolated from diseased tissues. Three isolates of R. solani were successfully anastomosed with R. solani isolate AG-1 (ATCC 58946) (Carling, 1996). Characteristics of mycelium and sclerotia were typical for subgroup IB. The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4 and sequenced (GenBank accession No. KC493639). BLASTn analysis (Altschul et al., 1997) of the amplified product 661 bp in size showed 99% homology with the sequence of Thanatephorus cucumeris (telomorph R. solani) JQ692294. The pathogenicity of one isolate was demonstrated, by placing mycelium disks on the leaves of 42 lavender plants which were then covered with plastic bags. The first symptoms developed two days post inoculation and R. solani was reisolated from affected plants. This is the first report of R. solani on L. officinalis in Italy.