Population genetic analysis of grapevine fanleaf virus

Abstract

Population genetic analysis of grapevine fanleaf virus (GFLV) was done on the basis of the virus movement protein (MP) gene sequences from the isolates detected and identified in this study and those of all previously reported GFLV strains/isolates. These revealed that the GFLV populations of Iran and Slovenia were highly distinct, whereas those of France, Germany, Italy and the USA were composed of multiple lineages. All populations were significantly differentiated from each other. However, two GFLV isolates from Tunisia, the only recorded GFLVs from that country, were not statistically distinct from the French, German and Italian populations. The ratio of non-synonymous nucleotide diversity to synonymous nucleotide diversity (Pi(a)/Pi(s)) was less than 1, suggesting that the MP gene has been under purifying selection. The neutrality tests were indicative of a balancing selection that is operating within Iranian and USA GFLV isolates, but they show a purifying selection within the other populations. Eleven recombination events were detected in a total of 50 isolates from France, Germany, Iran, Italy, Slovenia and the USA. The results from the recombination analysis were in agreement with those of the phylogenetic analysis. This study suggests that diversity among GFLV geographical populations resulted from possible host adaptation, recombination and founder effects.