Maize Iranian mosaic virus (MIMV) is a distinct member of the genus Nucleorhabdovirus . In this study, the genetic diversity of MIMV isolates collected from different geographical regions of Iran, different hosts and different symptoms was determined during 2015-2016. The sequences of the nucleocapsid protein, glycoprotein, and a 500 bp fragment of polymerase genes as well as non-coding regions were determined. Genetic diversity in coding regions was less than 1.3 % in nucleocapsid protein and glycoprotein genes and 1 % in polymerase gene. The diversity in non-coding regions was higher compared to ORFs especially between P and gene 3 (up to 14.7 %). In phylogenetic analysis no correlation was found between MIMV isolates and geographical regions, type of symptoms and hosts. The ratio of non-synonymous to synonymous polymorphic sites indicated purifying selection has acted upon the analyzed gene. Considering the fact that maize has been imported to Iran and its cultivation has increased in recent years it appears that MIMV has been transmitted from weeds or other field crops to maize by its planthopper vectors and likely, the dependence of MIMV on planthoppers for spreading can explain its low diversity. In this study, also expression of all MIMV genes in maize during 28 days post-inoculation (dpi) and in inoculative planthoppers, Laodelphax striatellus, was examined using quantitative RT-PCR (RT-qPCR) assay. Accumulation of MIMV P, gene 3, M, G and L transcripts relative to the N transcripts were determined and normalized to the 18S rRNA in maize plant and ribosomal protein S13 gene (RPS13) in planthopper using the comparative C T method. In plants, higher levels of the MIMV N transcripts were found relative to other transcripts while MIMV L transcripts were at lowest levels. The highest accumulation of MIMV transcripts was found at 14 dpi. At 21 dpi, we assessed the lowest transcript levels for all genes which increased again at 28 dpi, although in lower amounts than 14 dpi. In Laodelphax striatellus , MIMV M, G and L transcripts accumulated at lower levels than other transcripts. Gene 3 level was high in both plant and planthopper. Our results showed that transcript accumulation for the MIMV genes was similar in both hosts (maize and planthopper) and followed the pattern of sequential transcriptional attenuation from the 3? to the 5? end of the genome similar to vertebrate-infecting rhabdoviruses. These results indicate the regulation of virus gene transcription for this plant-infecting rhabdovirus is similar to some vertebrate-infecting rhabdoviruses reflects the amount of viral mRNAs is directly related to their demands in virus life cycle. New insights on genetic diversity mechanisms can play an important role to prevent the development of emerging viruses. The information on the low genetic diversity of MIMV will be helpful in production of maize cultivars with durable resistance. Keywords: Maize Iranian mosaic virus, Genetic diversity, RT-qPCR, Laodelphax striatellus, Gene expresion.