Apple mosaic virus (ApMV) is a widespread ssRNA virus which infects diverse species of Rosales. The phylogenetic analysis of complete capsid protein gene of the largest set of ApMV isolates discriminated two main clusters of isolates: one cluster correlates with Maloideae hosts and Trebouxia lichen algae hosts; a second with hop, Prunus, and other woody tree hosts. No correlation was found between clusters and geographic origin of virus isolates, and positive selection hypothesis in distinct hosts was not confirmed: in all virus populations, purifying selection had occurred. GGT→AAT substitution resulted in Gly→Asn change inside the zinc-finger motif in the capsid protein was revealed specific for discrimination of the clusters and we hypothesise that could influence the host preference.

Summary It has been previously shown that European mountain ash ringspot‐associated virus (EMARaV), a multipartite, negative‐strand RNA plant virus, is pathogenic for European mountain ash (Sorbus aucuparia L.). However, its transmissibility to and replication in other host species remains poorly understood. In this work, we performed experimental inoculations of seventeen virus‐tested species and interspecies hybrids of subfamily Maloideae (family: Rosaceae) with buds from EMARaV‐infected S. aucuparia trees. Surprisingly, a majority of the graft‐inoculated tree species, for instance Sorbaronia, Aronia and Amelanchier, developed symptoms typical for EMARaV infection. These symptoms included chlorotic spots of various size and shape and mottling on leaves but not on flowers and fruits. The propagation of EMARaV in graft‐inoculated tree species was subsequently confirmed by molecular detection tools. Based on these results, we carried out a systematic survey throughout the Czech Republic and identified the presence of EMARaV in wild growing trees in all explored regions, with massive disease infestation in several locations. More importantly, EMARaV infection was newly detected in S. aucuparia subsp. moravica, S. aucuparia × Crataegus sanguinea cv. Granatnaja, (Sorbus aria × Aronia arbutifolia) × S. aucuparia cv. Burka, cv. Finskaja (a Sorbus hybrid of unknown origin) and Aronia melanocarpa; all these EMARaV‐infested trees were grown in production orchards. The sequencing of the nucleocapsid (NC)‐coding gene from several of these EMARaV isolates provided insight into the population structure and phylogenetic relationships of the EMARaV variants occurring in the Czech Republic. Together, our biological and molecular findings extend our knowledge on the host range of EMARaV and provide the first evidence of its natural occurrence in hosts dissimilar to S. aucuparia.

Grimová L., Ryšánek P., 2012. Apricot latent virus -Review. Hort. Sci. (Prague), 39: 144-148.Apricot latent virus (ApLV) is a definitive species of the Foveavirus genus, the Betaflexiviridae family. Although the virus is not highly prevalent, it was identified in several European and Mediterranean countries thus far. Biological experiments demonstrated that, in addition to the only known natural host, Prunus armeniaca, ApLV can be experimentally graft-transmitted to several Prunus species. Therefore, the eradication of the viral pathogen largely depends on the use of virus-free propagating materials and rootstocks, which should be seriously considered when designing and implementing stone fruit certification schemes. Although ApLV is not present on the list of viruses and other pathogens that require testing in the EPPO certification schemes for the production of healthy stone fruit trees for planting, Peach asteroid spot disease (PAS) causing agent whose occurrence was often justly correlated with ApLV, is included on the list. This review summarises the current available knowledge of ApLV on the biological, morphological, physicochemical and molecular levels and includes the contemporary management approaches.

The phytosanitary status of wild growing stone fruit trees and shrubs was examined in surveys conducted in 2013 and 2014 in the region of Central Bohemia, Czech Republic. A total of 159 leaf samples were collected (42 cherries, 77 bird cherries, 10 cherry plums, 13 blackthorns, 2 round plums, 15 plums) and tested for the presence of Plum pox virus (PPV), Prunus necrotic ringspot virus (PNRSV), Prune dwarf virus (PDV), Apple mosaic virus (ApMV), Apple chlorotic leaf spot virus (ACLSV), Cherry virus A (CVA), Cherry necrotic rusty mottle virus (CNRMV), Cherry green ring mottle virus (CGRMV), and Cherry leafroll virus (CLRV) using reverse transcription-polymerase chain reaction (RT-PCR). Totally 28.3% of the investigated trees and shrubs were infected by at least one monitored virus. Mixed infection occurred in 5 out of 159 trees (3.1%). PPV was the most widespread virus (13.2% of samples), followed by PDV (11.3%). Contrary to these two most relevant viral pathogens, the incidence of CLRV and CVA was negligible in individually growing trees of the genus Prunus and ApMV, ACLSV, CGRMV, and CNRMV were not detected at all.

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