Zohreh Moradi - Department of Plant Pathology, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran
Mohsen Mehrvar - Department of Plant Pathology, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran
Ehsan Nazifi - Department of Biology, Faculty of Basic Sciences, University of Mazandaran, Babolsar, Iran

Zucchini yellow mosaic virus (ZYMV) is one of the most economically important viruses infecting cucurbitsworldwide. Population genetic analysis of ZYMV was conducted based on the virus cylindrical inclusion (CI) genesequences of 10 isolates identified in this study and 94 other isolates from different countries in six continents: Asia,Europe, Oceania, Africa, North and South America. The overall mean value of nucleotide sequence diversity among allisolates was 0.074±0.006. Phylogenetic analysis showed that ZYMV isolates fell into three main phylogroups withsignificant FST values (> 0.55) and almost tended to cluster according to their geographical position. Group I waspredominant and contained isolates originated from different parts of the world. Iranian isolates clustered into group I,sharing 87.7-99.7% and 92.5–100% nucleotide and amino acid identity, with other isolates of this group. Group II was anew group that included only Singapore isolates. Group III including East Timor, Reunion Island and Australia-Kununurra isolates which were genetically differentiated from other populations. ZYMV populations from differentgeographic origins were composed of multiple lineages. With exception of the Oceanian population which was stronglydifferentiated from the American population, most other geographical populations showed low to moderate geneticdifferentiation. There was moderate to high level of gene flow despite large separating geographic distances. Analysisof the synonymous-to-nonsynonymous ratio showed strong purifying selection in the CI gene. The analyses indicatedthat in addition to selection, random processes such as genetic drift and founder effects are important determinants forthe genetic structure of populations of ZYMV.

Cylindrical inclusion, Evolutionary forces, Genetic variability, Zucchini yellow mosaic virus