The use of serological differentiation indices for the phylogenetic analysis of plant virus relationships

Summary The potential use of serological differentiation indices (SDIs) in the phylogenetic analysis of plant virus coat protein relationships is presented. Relationship dendrograms were constructed from SDI data for viruses in the tymovirus and Subgroup I geminivirus taxonomic groups, using distance or phenetic methods embodied in the computer programmesFitch andNjtree. Relationship dendrograms for geminiviruses agreed well with those constructed by others from sequence or other data; the dendrogram for tymoviruses was not in agreement with one calculated from amino acid composition data, or from other properties, but appears consistent with recently-shown sequence similarities between tymoviruses. Implications of these results for the classification and taxonomy of plant viruses are discussed.