CROSS PROTECTION BETWEEN MAIZE DWARF MOSAIC VIRUS AND BERMUDA GRASS SOUTHERN MOSAIC VIRUS

Bermuda grass southern mosaic virus (BgSMV) and Maize dwarf mosaic virus (MDMV) despite a 90 nucleotide difference in coat protein (CP) gene are very similar in serological and molecular properties. In the present work, cross protection between BgSMV and MDMV was studied. The experiment consisted of five treatments in five replications (each replication consisting of one pot with 10 plants). The treatments consisted of mechanical inoculation of sorghum with each virus followed, after symptom appearance, by challenge inoculation with the other virus, simultaneous inoculation of both viruses, and single-virus inoculations. Two weeks after inoculations, plant samples were taken from treated plants and subjected to RT-PCR using mRNA Capture Kit (Roche) and specific primer pairs MD3F/MD1R and BgSMF90/ BgSMR90b. The results showed that prior infection of plants by either MDMV or BgSMV protects against super infection by the other virus. Based on these results and previous biological and molecular information, BgSMV and MDMV may be regarded as closely related viruses or the strains of the same virus despite their biological and molecular differences. Cross protection was also studied between each of these viruses and Iranian Johnson grass mosaic virus (IJMV) as control, and no cross protection was observed between IJMV and either MDMV or BgSMV.