Wild and globally traded ornamental aquatic plants harbor diverse plant viruses, including notable crop pathogens.

BACKGROUND: Aquatic plants play key roles in ecosystems, serving as primary producers and providing habitat for other aquatic life. While many are ecologically important, some invasive species, often introduced through the ornamental plant trade, pose threats to various aquatic ecosystems. Although viral infections have been documented to some extent in aquatic crops, the viral diversity in wild and ornamental aquatic plants remains largely unexplored. Investigating the viral communities of aquatic plants is important, as their direct contact with water allows for the potential long-distance transmission of stable viruses released from infected individuals. Invasive aquatic plants exacerbate this issue by introducing novel microbes, including viruses, to new regions, increasing the potential threat to native plant populations. RESULTS: Here, we investigated the viral communities of diverse aquatic plants by mining publicly available transcriptome data of 79 wild aquatic species and sequencing the RNA from 14 plant species (some of them of different ornamental varieties), sourced from hobby aquascaping stores. Plant viruses from various families were detected in taxonomically diverse aquatic plants, ranging from algae to angiosperms. Alongside sequences of known crop pathogens, such as turnip yellows virus, cucumber mosaic virus, and lettuce chlorosis virus, we identified contigs of putative novel viral species belonging to several plant-infecting viral families. Most notably, we discovered sequences of known and novel begomoviruses, which may be causing observed ornamental phenotypes in two different aquatic plants. Further, we identified a novel potyvirus that appears to be globally present in multiple ornamental plants from the genus Sagittaria. We detected it in three plants sourced from online stores in Slovenia, as well as six plants intercepted during the import process into the UK. CONCLUSIONS: Our findings expand on the so far limited knowledge of aquatic plant viruses, revealing known and putative novel plant viral species across diverse aquatic plant taxa. The detection of crop viruses, including regulated pathogens, in ornamental aquatic plants highlights the risks associated with their unregulated global trade. Further research into viruses of aquatic plants may provide insights into their role in ecosystems as well as their potential impact on agriculture.