Characterization of Coat Protein Gene of Cucumber Mosaic Virus Isolates in Iran

Background: Cucumber mosaic virus (CMV) from the Bromoviridae family, is one of the most widespread plant viruses in the world. Objectives: In the present study tomato fields in Guilan, Isfahan, Khorasan Razavi, Khuzestan and Tehran provinces were surveyed to determine the presence of CMV subgroups during 2011-2012. Materials and Methods: Out of 305 symptomatic leaf samples tested by Enzyme-linked immuno sorbent assay (ELISA), 147 samples (48.2 %) were found to be infected by CMV with the highest percentage in Khorasan Razavi (67.4%) followed by Khuzestan (50.6%), Tehran (48%), Isfahan (38.2%) and Guilan (34.3%). The coat protein (CP) gene in the 19 sequenced CMV isolates composed of 657 nucleotides (nt) in a size that encodes 218 amino acids. Phylogenetic analysis based on the nt CP gene showed that the ToKz1, ToKz2, ToKz3 and ToKz4 from Khuzestan fell into subgroup IB and the rest of the Iranian isolates including those sequenced in this study fell into subgroup IA. Results: Subsequent analyses showed that the Iranian CMV isolates belonging to subgroup IA of CMV were most related phylogenetically to each other and they were distinct from the subgroup IB and subgroup II isolates. Bioassay on Nicotiana glutinosa and Solanum lycopersicum showed that the symptoms caused by subgroup IB isolates from Khuzestan were milder than those caused by CMV isolates from subgroup IA under this study. Conclusions: In Iran only subgroups IA and II have been reported, however for the first time this study shows the occurrence and phylogenetic relationships of CMV subgroup IB isolated from tomato fields in West Asia, Iran.