Two sets of degenerate primers for the specific amplification of 572-575 nt and 386 nt segments of the methyltransferase and RNA- dependent RNA polymerase cistrons of members of the genera Tymovirus and Marafivirus and of the unassigned virus Grapevine fleck virus (GFkV) were designed on the basis of available sequences. These primers were used for amplifying and subsequent cloning and sequencing part of the open reading frame 1 of the genome of GFkV, Grapevine asteroid mosaic-associated virus (GAMaV) and of another previously unreported virus, for which the name Grapevine red globe virus (GRGV) is proposed. Computer-assisted analysis of the amplified genome portions showed that the three grapevine viruses are phylogenetically related with one another and with sequenced tymoviruses and marafiviruses. The relationships with tymoviruses was confirmed by the type of ultrastructural modifications induced in the host cells. RdRp-specific degenerate primers were successfully used for the aspecific detection of the three viruses in crude grapevine sap extracts. Specific virus identification was obtained with RT-PCR using antisense virus-specific primers.

Field surveys were carried out in the main stone-fruit-growing areas of East Anatolia (Turkey) to assess the sanitary status of varietal collections, mother blocks and commercial orchards. The presence of virus and virus-like diseases was ascertained by enzyme-linked immunosorbent assay (ELISA), sap transmission to herbaceous hosts, graft transmission to peach cv. GF305 and molecular hybridization tests. A total of 1019 samples was tested by ELISA (859 apricot, 120 cherry, 21 almond and 19 peach). The sanitary status of apricot was extremely satisfactory, as the infection level was less than 0.3%. Cherry and almond, however, showed 21% and 33% infection respectively. The viruses identified were apple chlorotic leaf spot trichovirus (ACLSV), prune dwarf ilarvirus (PDV) and prunus necrotic ringspot ilarvirus (PNRSV). The commonest virus was PDV. Plum pox potyvirus (PPV), apple mosaic ilarvirus (ApMV) and the nepoviruses tomato black ring (TBRV), raspberry ringspot (RpRSV), strawberry latent ringspot (SLRV), cherry leaf roll (CLRV), arabis mosaic (ArMV) and tomato ringspot (ToRSV) were not encountered. Peach latent mosaic viroid (PLMVd) and hop stunt viroid (HSVd) were not detected either.