Nucleotide sequence of the 3 ' terminal region of the genome of four Lettuce mosaic virus isolates from Greece and Yemen

Lettuce mosaic virus (LMV) is an economically important Potyvirus causing a severe disease of commercial lettuce crops. Based on molecular data, three phylogenetic groups of isolates have previously been discriminated, reflec ting their geographical origin (Western Europe-California, Greece, or Yemen ). Sequence information for the entire coat protein domain was only availab le for one of the Western Europe-California phylogenetic group. We have now sequenced the 3' terminal region of the genome LMV-Gr4, -Gr5 and -GrB, iso lates which belong to the Greek phylogenetic group and of LMV-Yar, the sole known representative of the third LMV phylogenetic group. The region seque nced encodes the last 62 amino-acids of the polymerase and the entire coat protein of the four isolates, plus the 3' non-translated region of LMV-Gr5 and -Yar. The Greek and Yemenite isolates studied are all very aggressive o n lettuce, are able to overcome the resistance genes mol(1) and mol(2) and belong to the two phylogenetic groups which have so far been only partially characterised. As for other Potyviruses, the core and the C-terminal regio ns of the coat protein are highly conserved among all isolates whereas the N-terminus is more variable. No amino acid change in the coat protein or ca rboxy-terminal part of the polymerase could be related to the resistance-br eaking properties of the isolates analysed. The sequences obtained provide the basis for the rapid typing of LMV isolates using the restriction patter n of segments of cDNA amplified by PCR.