First report of European mountain ash ringspot-associated virus in serviceberry (Amelanchier spp.) in Germany

Chlorotic ringspots and line pattern have been observed in different species of serviceberry (Amelanchier spp.), for instance in the Netherlands since 1957 (Cooper, 1979). Being tolerant against various abiotic stresses these shrubs are often used in urban green space and also have decorative flowers, berries and a red leaf colouration in the autumn.

Serviceberry shrubs cultivated in public or private urban areas in the cities of Oldenburg (Lower Saxony) and Berlin, Germany exhibiting chlorotic ringspots, mottle and line patterns on the leaves were sampled (Fig. 1, Table 1). The disease resembled characteristic symptoms caused by European mountain ash ringspot-associated virus (EMARaV) in serviceberry (Grimová et al., 2015). To confirm the presence of the virus in these samples, total RNA was extracted and tested by RT-PCR using a genus-specific primer set to detect RNA1 (Elbeaino et al., 2013) and EMARaV-specific primers targeting RNA2, RNA3 (Mielke & Mühlbach, 2008) and RNA4 (Roßbach et al., 2015). All four RNAs of EMARaV were detectable in each of the four serviceberries exhibiting symptoms (Fig. 2) and this was confirmed by sequencing of the PCR products. Complete viral genome segments were amplified by RT-PCR from sample E55282 using primers targeting the conserved terminal regions of emaraviruses (Di Bello et al., 2015). PCR products were cloned and sequenced confirming the complete RNA3 (1.6 kb, GenBank Accession No. LT992915) and RNA4 (1.3 kb, LT992916) of EMARaV. Sequence comparison with respective reference sequences from GenBank and generation of a neighbour-joining phylogenetic tree using complete sequences of the nucleocapsid protein encoded by RNA3 of emaraviruses (Fig. 3) confirmed the virus as EMARaV with a maximum of 99.6 % (RNA3) and 99.1 % (RNA4) identity at the protein level.

This is the first record of EMARaV affecting serviceberry and causing chlorotic ringspots, mottling and line patterns in Germany. The virus has previously been confirmed to be widespread in Sorbus aucuparia in Germany (Roßbach et al., 2015). The disease identified in Germany shares characteristic symptoms reported from EMARaV-infected serviceberry in the Czech Republic (Grimová et al., 2015). It has been demonstrated that the causal agent is graft transmissible within species of the Rosaceae family including serviceberry and rowan (Cooper, 1979; Grimová et al., 2015). How the diseased serviceberries acquired the virus in independent locations in Germany is unknown as modes of transmission other than grafting are not well documented for EMARaV.