First report of botrytis blight caused by Botrytis cinerea on Rudbeckia hirta in Italy.

Abstract

In February 2014, symptoms of a previously unknown blight were observed in plants of Rudbeckia hirta grown in an experimental glasshouse of Agroinnova at Grugliasco (Piedmont, northern Italy). Necrotic areas appeared on leaves and stems that rotted and desiccated. A soft, grey mycelium developed on affected tissues. From infected plants a fungus was consistently isolated that produced a soft and grey mycelium, with branched conidiophores and unicellular, ovoid, conidia measuring 13.3-7.5×9.1-6.2 (average 9.5×7.2) μm. These morphological features 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. KJ698646). BLAST analysis (Altschul et al., 1997) of the 493 bp segment showed a 99% similarity with the comparable sequence of Botryotinia fuckeliana (KF667540). For pathogenicity tests, three healthy plants of R. hirta were sprayed with a spore and mycelial suspension (1.4×104 conidia/ml) of the pathogen whereas controls were sprayed with water only. All plants were covered with plastic bags for six days. Three days post inoculation symptoms developed on inoculated plants from which B. cinerea was consistently reisolated. Control plants remained healthy. This is the first report of B. cinerea on R. hirta in Italy and worldwide.