FIRST REPORT OF HOSTA VIRUS X (HVX) INFECTING HOSTA IN ITALY

Species of Hosta (Liliaceae) are herbaceous perennials more often grown for their foliage (blue, gold, green or variegated) then for their flowers. Virus diseases reported elsewhere in the word on cultivated hosta species include Hosta virus X (HVX), first described in USA in 1996, and considered to be the main pathogen of this genus. In October of 2010, the following systemic virus-like symptoms were observed on leaves of three varieties cultivated in Emilia-Romagna region (Italy) (“Gold Standard”, “Sum and Substance” and “Whirlwind”): irregular green blotched scattered in the yellow lamina, green bands running along the veins having an “ink-bleeding” look, malformations, different leaf thickness. Electron microscopic observations revealed the presence of virus particles ca. 560-600 nm in length, which in ISEM and PAS-ELISA tests clearly reacted with the antiserum to HVX (provided by University of Minnesota, MN, USA). Mechanical inoculations carried out using symptomatic hosta leaf sap made it possible to transmit HVX to Chenopodium murale L. (necrotic pin-point lesions) and Gomphrena globosa L. (necrotic red spots 2-3 mm in size). By applying RT-PCR with specific primers HVXCP+ 5’-ATGGCAAGTGACGCACCAACTCCACC-3’ and HVXCP- 5’- TCAACTTGAGCCTTCCGGG-3’ that amplified a fragment of 663 nt based on the coat protein gene, HVX appeared closely related to polish isolate FJ821705 (98% nucleotide identity). To prevent HVX spread it is important to minimize mechanic contact between plantlets during cultivation, and immediately remove those showing visible virus-like symptoms. Considering that two of the infected varieties tested have been imported from Holland, certified virus-free propagation material must be requested.