Detection and Molecular Characterization of Two New Isolates of Iranian johnsongrass mosaic virus in Corn Fields of Mazandaran Province

The genus Potyvirus is one of the largest and economically important groups of plant viruses, due to their effects on crops worldwide. Potyviruses are accounted for 40% of viral diseases of various plants. Iranian johnsongrass mosaic virus (IJMV) is one of the important potyviruses infecting cereal crops and one of the main causal agents of maize mosaic in Iran. In order to study the this virus, 90 samples showing virus-like symptoms were collected from different maize fields in Mazandaran province during 2013-2014 and evaluated with DAS-ELISA test using polyclonal specific antibody. RT-PCR assay with degenerate primers corresponding to the virus CI gene led to the amplification of the expected DNA fragment with a length of 680 bp in all ELISA-positive samples. Two fragments were cloned in a pTG19-T vector and sequenced. BLAST analysis of the sequenced data confirmed that the PCR-amplified fragments belonged to IJMV. Phylogenetic analysis based on partial sequences of CI gene showed that these two isolates of IJMV had the highest nucleotide (84.2%) and amino acid (97.3%, 97.8%) identities and a close phylogenetic relationship with another Iranian isolate of IJMV namely Shz (JQ692088) isolated from Johnsongrass and previously reported from Shiraz. High-nucleotide differences between the IJMV isolates obtained from maize and Shz isolate from johnsongrass indicating high nucleotide variability of this potyvirus. These results demonstrated the occurrence and spread of IJMV in the maize fields of Mazandaran province based on serological test, RT-PCR, and CI gene analyses.