Effect of temperature on disease severity of Maize dwarf mosaic and Bermuda grass southern mosaic viruses*

Bermudagrass southern mosaic virus (BgSMV)and Maize dwarf mosaic virus (MDMV) are closely related potyviruses varying in geographical distribution and the existence of an additional 90- nucleotide stretch in the 5 'region of coat protein gene. .In the present study, the effect of temperature on disease severity of both viruses was assessed. A factorial experiment was conducted laid out in a completely randomized design with two factors, temperature at three levels (25, 30 and 35°C) and inoculation at three levels (MDMV, BgSMV and buffer) each in six replications. Eleusine compressa, a common host of both viruses, was inoculated mechanically and disease severity, length of incubation period, plant height, and plant weight were measured 30 days post inoculation. Disease severity of MDMV was not significantly affected by temperature change but that of BgSMV increased with increasing temperature. Incubation period of MDMV inoculated plants decreased with increasing temperature. Bioinformatics analysis showed presence of a coiled-coil region in CP of both viruses. This region was longer in BgSMV extending into extra amino acids in amino terminal region. Extra amino acid stretch may contribute to the adaptation of this virus to higher temperatures.