Sorbaria tomentosa - a new natural host for Potato virus Y (PVY)

Sorbaria tomentosa syn. Spiraea sorbifolia (Family Rosaceae), common name False Spiraea, is a large, woody shrub with creamy-white flowers. Various species of the related genus Spiraea, have been reported to be hosts of Arabis mosaic virus, Cucumber mosaic virus, Spiraea yellow leafspot virus and Spiraea leafspot spherical virus (Polak & Kontzang, 1993; Lockhart et al., 2002). During a virus survey in natural plant vegetation of the Northwest Himalaya of Himachal Pradesh, Sorbaria plants showing leaf mosaic symptoms were observed. Symptomatic leaves were screened for the presence of viruses by ELISA using specific antibodies. Positive results were obtained using antibodies specific to the potyvirus group (Agdia, Elkhart, USA). To confirm the virus group detected, leaf samples were tested using a universal potyvirus primer pair that amplifies part of the coat protein gene and the 3'-UTR of the viral genome (van der Vlugt et al., 1999). An amplification product of the expected size (~800bp) was obtained using RT-PCR (Fig. 1). The RT-PCR product was cloned, sequenced and the data submitted to the EMBL Database (Acc. No. AJ867285). The amplicon sequence showed 98% homology to isolates of Potato virus Y (PVY) from the United Kingdom (AJ390303, AJ585197), Switzerland (X97895), New Zealand (M22470) and Brazil (AF255660). This is the first report of a potyvirus occurring naturally in S. tomentosa. This plant should be considered a potential reservoir of PVY, especially since the aphid species Myzus persicae and Rhopalosiphum rufiabdominalis have been reported to colonize related Spiraea spp. in Himachal Pradesh (Mishra & Parihar, 1985). Sorbaria grows along the margins of cultivated fields and has been identified as a potential natural reservoir host for PVY and its aphid vectors. Therefore, growers should attempt to eradicate diseased Sorbaria plants from the vicinity of crop fields, wherever feasible.