First Report of Cherry leaf roll virus in Hydrangea macrophylla.

Abstract

Hydrangea is a popular, summer flowering, ornamental shrub that is native to south and east Asia and North and South America, which is now cultivated throughout the world. Currently, 13 viruses belonging to eight genera have been reported in Hydrangea spp. (1). In April 2011, virus-like disease symptoms, including severe leaf deformation and chlorosis, were observed on two Hydrangea macrophylla 'Sumiko' plants from Australia being held in quarantine in New Zealand. Systemic symptoms of veinal necrosis, necrotic halo spots, and severe leaf deformation were observed on Nicotiana occidentalis '37B' 7 days after inoculation with sap from the symptomatic hydrangea plants. Upon reinoculation with sap of symptomatic leaves from N. occidentalis, necrotic ringspots and tip necrosis, typical of nepovirus infection, were observed on leaves of N. tobacum and Chenopodium quinoa, respectively. Transmission electron microscopy of negatively stained sap from symptomatic leaves of N. occidentalis revealed the presence of isometric particles ~28 nm in diameter. Total nucleic acid was extracted from the symptomatic leaves of N. occidentalis with an InviMag Plant DNA Mini Kit (Invitek GmbH, Berlin, Germany) and a KingFisher mL workstation (Thermo Scientific, Waltham, MA). Reverse transcription (RT)-PCR using the reverse primer of Werner et al. (2) and a forward primer, 5'-CGGTGGAGATGCCGGTCCTA-3' (this study), specific to the 3'-untranslated region (3'-UTR) of Cherry leaf roll virus(CLRV) produced an amplicon of ~1,150 bp from N. occidentalis. A consensus sequence of 1,140 bp generated from four clones of the PCR product (GenBank Accession No. JN418885) was 99 and 98% identical at the nucleotide level to a CLRV isolate from Rumex AGBC (GenBank No. AB168099) and Chinese chives (GenBank No. AB168098), respectively. N. occidentalis also tested positive for CLRV using polyclonal antiserum in a double antibody sandwich-ELISA (BIOREBA, Reinach, Switzerland). The presence of CLRV in the original samples and N. occidentalis was confirmed by direct sequencing of the 380-bp amplicons obtained by immunocapture RT-PCR using CLRV-specific primers (2) and the same antiserum. BLASTn analysis of these amplicons (data not submitted to GenBank) also showed 99% nucleotide identity to a New Zealand isolate from a Rubus sp. (GenBank No. AJ877162). The hydrangea plants were released from quarantine because the same strain of CLRV had previously been reported in New Zealand. To our knowledge, this is the first report of CLRV in hydrangea. CLRV is a seed and pollenborne nepovirus and can be transmitted mechanically and by grafting. Since hydrangeas are mainly vegetatively propagated and are less commonly grown from seeds, the natural spread of CLRV will depend on the movement of infected propagation material. It is unknown whether this virus causes reduction in flower quality in hydrangea as reported in other hosts but any impact on flower quality may be of economic significance in commercial nurseries.