VARIANTS OF APRICOT LATENT FOVEAVIRUS (ALV) ISOLATED FROM SOUTH EUROPEAN ORCHARDS ASSOCIATED WITH PEACH ASTEROID SPOT AND PEACH SOOTY RINGSPOT DISEASES

The purpose of this study was to investigate the aetiology of two degenerative diseases of peach originally transmitted by graft-inoculation from apricot, the peach asteroid spot and the peach sooty ringspot diseases previously characterised at the Ctifl center of Lanxade by J.C. Desvignes and colleagues. Two isolates, named respectively LA2 for the peach asteroid spot disease and Caserta-12 for the peach sooty ringspot disease, were propagated on GF305 peach seedlings and on Nicotiana occidentalis and assessed for the presence of dsRNAs. Double stranded RNAs could be purified from plants infected with either of these isolates, and were submitted to SMARTTM long distance RT-PCR (LD-PCR). For LA2 a polyadenylated, 1151 bp long cDNA was cloned and sequenced. For isolate Caserta-12 an approximately 4 kbp polyadenylated cDNA was cloned and partially sequenced. These cDNAs encode the last 327 amino acids of the LA2 coat protein and the last 202 amino acids of the Caserta-12 coat protein. The partial coding sequences thus obtained revealed respectively 96% and 97% identity with the sequence encoding the coat protein of Apricot latent virus (ALV), a Foveavirus serologically related to ASPV. Close relatedness between ALV and the agents present in the LA2 and Caserta 12 isolates was also demonstrated by hybridisation of total RNA extracts of GF305 seedlings graft-inoculated with ALV, LA2 and Caserta-12 with ALV or LA2-specific cRNA probes. Polyvalent nested RT-PCR allowed us to amplify a 362 bp cDNA encoding part of the RNA dependent RNA polymerase of these three agents from silica-captured nucleic acid extracts of infected N. occidentalis and GF305 peach. The sequencing of these amplicons confirmed the close relationship of this three members of the Foveavirus genus.