Ecological and Genomic Perspectives on the Interactions of a Wild Marafivirus (Family Tymoviridae) with its Prairie Grass Host

Switchgrass mosaic virus (SwMV) is a wild marafivirus native to North America that commonly infects Panicum virgatum (switchgrass), a genetically diverse perennial grass with a broad geographic range. Switchgrass is important both as a co-dominant species in remnant native prairies and as a candidate bioenergy feedstock. The latter role has driven the creation of extensive genetic resources, including reference genomes and tools for genome-wide association studies (GWAS). Since most studies of virus – host interactions have focused on crop viruses in domesticated plants, having access to such genomic resources for a wild species like switchgrass presents a rare opportunity to probe how wild hosts interact with wild viruses in nature. This seminar will highlight insights from multi-year studies of SwMV infection in switchgrass, including GWAS of disease expression across a broad diversity panel. Ecological findings reveal that SwMV’s leafhopper vector enables the virus to quickly colonize and exert significant pressure on wild host populations—even when these populations are sparsely distributed within agricultural landscapes. Resistance to SwMV disease varies markedly among geographic and ecotypic subpopulations, suggesting that these groups have experienced distinct evolutionary trade-offs in response to virus pressure. In parallel, GWAS results identify a broad suite of candidate genes associated with SwMV disease expression. Together, these findings position switchgrass as a powerful model for studying virus dynamics in natural systems and offer needed insight into virus–host coevolution beyond agricultural contexts.