Archivio Journal of Plant Pathology

Abstract:

In June 2014, in a nursery of the Agroinnova Centre (Torino, northern Italy) and later in a garden near Biella (northern Italy), several 60- to 90-day-old plants of nettle-leaved bellflower (Campanula trachelium) were observed, that showed water-soaked lesions on the stems. Subsequently, the foliage blighted, turned brown, clung to the shoots, and matted on the surrounding plants. Eventually, infected plants died. Rhizoctonia solani was consistently recovered from diseased tissues in pure culture on potato dextrose agar (PDA). One of the fungal isolates was paired with R. solani tester strains. The C. trachelium isolate anastomosed (low fusion frequency) only with the AG 1 strain (ATCC 58946) (Sneh et al., 1991). Mycelium and sclerotia were typical for AG 1-IB. The internal transcribed tpacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4, and sequenced (GenBank accession No. KP792749). BLAST analysis (Altschul et al., 1997) of the 510 bp amplified sequence showed a 100% similarity with the sequence of R. solani KM589032. For pathogenicity tests, one of the isolates was tested by placing mycelial fragments removed from PDA cultures close to 10 healthy of C. trachelium plants, which were then maintained at 22-25°C. The first symptoms, similar to those observed in the nursery, developed 5-7 days post inoculation and R. solani was consistently reisolated from inoculated plants. By contrast, control plants, inoculated with sterile PDA fragments, remained healthy. This is the first report of R. solani on C. trachelium in Italy as well as worldwide.