First Report of Apricot pseudo-chlorotic leaf spot virus Infecting Plum (Prunus domestica) in the Czech Republic.

Apricot pseudo-chlorotic leaf spot virus (APCLSV) is a novel, still poorly known Trichovirus in the family Betaflexiviridae. It is most closely related to Apple chlorotic leaf spot virus (ACLSV) (2,4) and infects stone fruit trees of the Prunus genus. Its presence has so far been detected in apricot, plum, Japanese plum, and peach trees in Italy, Spain, France, Hungary, Turkey, Jordan, and Australia (1,2,4). During the summers of 2008 and 2010, leaf samples of old Czech local plum cultivars were obtained from the Holovousy collection and assessed for the presence of viruses belonging to the Capillovirus, Trichovirus, and Foveavirus genera using the polyvalent degenerate oligonucleotides (PDO) nested reverse transcription (RT)-PCR test (3). Following amplification from total RNAs extracts, the amplicons were cloned and several clones were sequenced for each plant sample. In plum (Prunus domestica) cv. Babce, a mixture of amplicons was observed and BlastN and BlastX analyses of the obtained sequences revealed the presence of ACLSV and APCLSV. The 310-bp APCLSV amplicon (GenBank Accession No. JN790294) showed highest identity (82.9% in nucleotide sequence and 97.1% in amino acid sequence) with the Sus2 isolate of APCLSV (4) and clustered with APCLSV isolates in a phylogenetic analysis. APCLSV infection was further confirmed with an APCLSV-specific RT-PCR assay (4), which yielded a product of the expected 205-bp size (GenBank Accession No. JN653070) with closest homology again to the Sus2 APCLSV isolate (83.4 and 94.3% nucleotide and amino acid identity, respectively). To our knowledge, this finding represents the first detection of APCLSV in domestic plums in the Czech Republic, extending our vision of APCLSV diversity and its geographic distribution. For unknown reasons, APCLSV has almost always been reported in mixed infection with ACLSV (1,2,4) and the situation in cv. Babce does not deviate from this trend. This has greatly hindered the analysis of the pathogenicity of APCLSV, a situation further complicated in the current case because the Babce cultivar was also infected by Plum pox virus. References: (1) M. Barone et al. Acta Hortic. 781:53, 2008. (2) T. Candresse et al. Virus and Virus-Like Diseases of Pome and Stone Fruit Trees. A. Hadidi et al., eds. The American Phytopathological Society, St. Paul, MN, 2011. (3) X. Foissac et al. Phytopathology 95:617, 2005. (4) D. Liberti et al. Phytopathology 95:420, 2005.