Archivio Journal of Plant Pathology

Abstract:

In January 2014, a previously unknown leaf and stem blight was observed on Rudbeckia fulgida grown in a glasshouse of the Agroinnova Centre, in Grugliasco, northern Italy. In June 2014, the same symptoms appeared on R. fulgida cultivated in a private garden near Biella, northern Italy. The morphological characteristics of the fungus isolated from infected tissues were typical of Botrytis cinerea (Ellis, 1971). The Internal Transcribed Spacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4, and sequenced (GenBank Accession No. KJ698645). BLAST analysis (Altschul et al., 1997) of the 489 bp segment showed a 99% similarity with the sequence of Botryotinia fuckeliana GU395993. In pathogenicity test, symptoms were reproduced on plants of R. fulgida sprayed with a spore and mycelial suspension of the pathogen and B. cinerea was consistently reisolated. Controls sprayed only with water remained healthy. This is the first report of B. cinerea on R. fulgida in Italy. Fifteen isolates of B. cinerea obtained from R. fulgida were evaluated in vitro on PDA amended with increasing concentrations of fungicides. Five strains were resistant to benzimidazoles (ED50 > 100 mg/l, M.I.C. > 300 mg/l), while 3 strains out of 15 showed a reduced sensitivity to iprodione (ED50 5 mg/l, MIC 10 mg/l).