DETECTION OF ALFALFA MOSAIC VIRUS BY IC-RT-PCR IN VIBURNUM OPULUS L.

Viburnum opulus L. (“snowball”, Caprifoliaceae) is a deciduous shrubs used as decorative plants for its fragrant white flowers that bloom in spring. In May 2011, snowball plants showing a virus-like disease were observed in two ornamental public gardens in Imola (Bologna, Emilia Romagna region). Symptoms appeared distributed on only part of the foliage, and consisted of chlorotic rings and spots, line-patterns and, in some cases, vein clearing on younger leaves. Since only Alfafa mosaic virus (AMV) and Cucumber mosaic virus (CMV) have been reported to naturally infect this Viburnum species, and considering that snowball could be an important source of virus infection, symptomatic plants were examined by applying Immunocapture Reverse Transcription-Polymerase Chain Reaction (IC-RT-PCR). Tests were performed on leaf extracts using two polyclonal antisera against an AMV isolate from lettuce and CMV isolate from tomato, respectively. Only AMV was found infecting symptomatic V. opulus. The CPAMV1/CPAMV2 specific AMV primer pairs were used in RT-PCR reactions. A DNA fragment of c.a. 750 bp, covering the entire coat protein gene (CP) of AMV, was obtained after IC-RT-PCR and the product was gel purified and cloned in pGEMT Easy for sequencing. Comparison of the CP sequence of AMV-V. opulus with the CP reference sequences of some AMV isolates, revealed the maximum nucleotide identities with subgroup I isolates. AMV has been previously found infecting V. opulus in Italy in 1995, but the leaf symptomatology observed was only vein yellowing.