DETECTION OF A REGION OF THE COAT PROTEIN GENE OF GRAPEVINE FANLEAF VIRUS BY RT-PCR IN THE NEMATODE VECTOR XIPHINEMA-INDEX

A region of the coat protein (CP) gene of grapevine fanleaf virus (GFLV) was detected by RT-PCR in the nematode vector Xiphinema index. The reverse transcription step was performed with total RNA extracted from viruliferous X. index. From the synthesized first cDNA strand, an 810-nucleotide fragment (nt 2515-3324 of GFLV-RNA2) was amplified by two 25-mer primers designed in the CP gene. Specific detection was successfully accomplished with samples of one or 10 viruliferous nematodes. Preliminary analysis and comparison of the 207-nt sequence of a stretch (nt 2549-2755 of GFLV-RNA2) of five different RT-PCR amplified fragments, obtained from 10 nematodes of a same sample in a diseased vineyard, indicated substantial variations in the GFLV CP gene. The deduced amino acid sequences showed important mutations essentially for two clones in four positions (residues 180, 188, 217, and 234 of the CP).