Evidence for two distinct subgroups of Alfalfa mosaic virus (AMV) from France and Italy and their relationships with other AMV strains - Brief report

The nucleotide sequence of the putative coat protein open reading frame of seven previously uncharacterized AMV strains from Italy and France was dete rmined and aligned with comparable sequences of other AMV strains (425 L, 4 25 M, YSMV, S, VRU, 15/64 and Dal. The data set of AMV sequences was used t o determine phylogenetic relationships by both a stochastic (stationary Mar kov model) and a deterministic method (maximum-parsimony) of analysis. The topology of the trees obtained with the two methods was essentially the same showing that all AMV strains clustered in two monophyletic groups. Cl ose clustering of Italian strains in subgroup I and of French strains in su bgroup II seems to suggests the effect of geographic distinctiveness of evo lutionary dynamics of these AMV strains. This separation did not correlate with differences in host range or symptoms (necrotic or non necrotic) induc ed in tomato but rather it reflected variations in the amino acid sequence of their CP, which might be related to structural properties of virus parti cles. A simple and rapid procedure based on the reverse transcriptase-polymerase chain reaction (RT-PCR) followed by ezymatic digestion (RFLP) was developed to identify and classify AMV isolates into the two subgroups. The method a pplied to a number of other AMV isolates from Italy and France supported th eir division in two distinct subgroups. This RT-PCR RFLP method may be usef ul way to investigate the dynamics of AMV populations in nature.