HCS Spring Seminar Series
Title: Populations and biology of viruses associated with Maize lethal necrosis in East Africa
Speaker: Lucy Stewart, USDA-ARS
Maize lethal necrosis (MLN) has emerged in East Africa, Asia, and South America since 2011, creating a need to examine contributing virus and vector populations. MLN is caused by synergistic co-infection of aphid-transmitted sugarcane mosaic virus (SCMV) or any of several related potyviruses and thrips-transmitted maize chlorotic mottle virus (MCMV). We examined populations of MCMV and SCMV in East African countries with MLN emergence (Kenya, Uganda, Rwanda, and Tanzania), and found significant diversity of potyviruses compared to MCMV. A new isolate of Johnsongrass mosaic virus, JGMV-EA was discovered, which contributes to MLN in East Africa and is not detected by diagnostics targeting SCMV. We made recommendations for improved broad spectrum detection of potyviruses. In addition to the known MLN-causing viruses, examination of maize viruses in MLN studies resulted in discovery of several other previously unknown maize-associated viruses. One ubiquitous virus is a novel polerovirus with several names in the literature, frequently termed “maize yellow mosaic virus”. We characterize the symptoms and pathology of this virus and biological properties including aphid vectors. Finally, research going forward on novel viruses and of thrips which are likely propelling MCMV emergence and therefore MLN emergence will be described.