Characterization of a new nepovirus infecting apricot in Southeastern France: Apricot latent ringspot virus

A pathogen was transmitted from apricot trees showing symptoms of viral inf ection to GF305 peach seedlings which reacted by stunting, shortened intern odes and chlorotic mottling. The agent was transmitted to cherry, apricot, peach and plum by grafting and to several herbaceous hosts by mechanical in oculation. Isometric nepovirus-like particles of 30-31 nm diameter extracte d from infected Chenopodium quinoa sedimented as two peaks in sucrose gradi ents. These particles contained two single stranded RNAs of approximately 5 .9 and 7.9 kb, and a single coat protein subunit of 53.7 kDa. No cross-reac tions were observed with a number of nepoviruses infecting fruit trees. Ino culation of purified particles to herbaceous or woody hosts reproduced the same symptoms caused by the original isolate. Sequencing of a 2.2 kbp cDNA clone covering the 3' end of the small genomic RNA identified an open readi ng frame encoding a 317 aa N-truncated protein exhibiting significant simil arities with the coat protein of nepoviruses. The 1257 nt long 3' non-codin g region showed up to about 65% homology to the equivalent region of member s of the subgroup C of nepoviruses. The properties of this pathogen do not match those of any previously described nepovirus. It should therefore be c onsidered as a new member of the subgroup C of nepoviruses, for which the n ame of Apricot latent ringspot virus (ALRSV) is proposed. The nucleotide sequence reported in this work has been deposited in the EMB L databank under the accession number AJ278875.