Spiraea, a group of ornamental shrubs in the Rosaceae family, are beloved by many for their clusters of petite flowers. Starting in 2024, leaf samples of Spiraea plants from commercial nurseries in five US states showing yellow spot symptoms were submitted to the UMN Plant Disease Clinic, but testing did not identify the pathogen as any of the existing four viral diseases of spiraea plants. Using high-throughput sequencing (HTS) technology, PhD student Joana Serrano Salgado and colleagues were able to identify two previously-unknown plant pathogenic viruses. One, from the Emaravirus genus, was found to be strongly associated with SCLDV symptoms. Serrano Salgado co-authored the paper with labmates Ronan Keener and Milenka Vera, PI Robert Alvarez Quinto, Brett Arenz of the UMN Plant Disease Clinic, Dimitre Mollov of USDA APHIS, and Pavel Killmov of Purdue University.
Using 77 spiraea leaf samples from Minnesota, Indiana, New York, Ohio, and Oregon, Serrano Salgado and colleagues set out to identify the pathogens. With HTS, made possible in part by high-performance computing from the Minnesota Supercomputing Institute, the research team were able to sequence genomes of the viruses present in the samples. For complete information about the diagnostic and sequencing processes, please read the full publication in Archives of Virology.
In the process, Serrano Salgado and colleagues discovered that two of the viruses infecting spiraea in the United States were not previously described: Spiraea chlorotic leaf distortion virus (SCLDV; genus Emaravirus) and Spiraea alpacytorhabdovirus 1 (SpCRV-1; genus Aphacytorhabdovirus). Powerful HTS technology is largely responsible for making these diagnoses possible, especially due to the complexities of these specific viruses themselves that make them trickier to diagnose through traditional virus purifications, like the lipid bilayer of Emaravirus species. This study also brought mites into the mix, as the frequency of eriophyid mites on the plants infected with the newly-characterized Emaravirus led researchers to wonder if mites served as a vector, transporting these viral pathogens to new spiraea plants. Further studies will be needed to discover whether the mites are a causal factor or just a correlation.
Serrano Salgado, J., Vera, M., Keener, R. et al. Discovery of a novel emaravirus and an alphacytorhabdovirus infecting Spiraea in the USA. Arch Virol 171, 205 (2026). https://doi.org/10.1007/s00705-026-06640-2