|WIJERATNE, SARANGA - The Ohio State University|
|Redinbaugh, Margaret - Peg|
|MASSAWE, DEOGRACIOUS - The Ohio State University|
|NIBLETT, CHARLES - Venganza Inc|
|ASIIMWE, THEODORE - Rwanda Agriculture Board (RAB)|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2017
Publication Date: 4/14/2017
Citation: Stewart, L.R., Willie, K.J., Wijeratne, S., Redinbaugh, M.G., Massawe, D., Niblett, C.N., Asiimwe, T. 2017. Johnsongrass mosaic virus contributes to maize lethal necrosis in East Africa. Plant Disease. 101(8):1455-1462. https://doi.org/10.1094/PDIS-01-17-0136-RE.
Interpretive Summary: Since 2011, Maize lethal necrosis (MLN) has emerged as a devastating corn disease in East Africa. MLN is caused by co-infection of two unrelated viruses: maize chlorotic mottle virus (MCMV) and any one of a number of related viruses (potyviruses), of which sugarcane mosaic virus is known to be prevalent in East Africa. In surveys across Kenya, Uganda, Tanzania, and Rwanda where MLN has emerged, we identified another virus present in sympotomatic samples: johnsongrass mosaic virus (JGMV). JGMV has never been reported in East Africa previously and was not known to be present in that part of the world. We characterized East African isolates of JGMV and found that it is different from isolates previously reported in Australia, the U.S., Brazil, and Nigeria, particularly in the coat protein sequence. We also showed that JGMV can cause MLN in co-infections with MCMV. These findings are important for diagnostics and containment of the viruses that cause MLN, and for understanding all the pathogens contributing to this high-impact disease.
Technical Abstract: Maize lethal necrosis (MLN), a severe virus disease of maize, has emerged in East Africa in recent years with devastating effects on production and food security where maize is a staple subsistence crop. In extensive surveys of MLN-symptomatic plants in East Africa, sequences of Johnsongrass mosaic virus (JGMV) were identified in Uganda, Kenya, Rwanda, and Tanzania. The East African JGMV is distinct from previously reported isolates, and infects maize, sorghum, and Johnsongrass but not wheat or oats. This isolate causes MLN in co-infection with Maize chlorotic mottle virus (MCMV), as reported for other potyviruses, and was present in MLN-symptomatic plants in which the major East African potyvirus, Sugarcane mosaic virus (SCMV), was not detected. Virus titers were compared in single and co-infections by quantitative reverse transcriptase-polymerase chain reaction. MCMV titer increased in co-infected plants whereas SCMV, MDMV, and JGMV titer was unchanged compared to single infections at 11 days post-inoculation. Together, these results demonstrate the presence of an East African JGMV (JGMV-EA) that contributes to MLN in the region.