Herbaria as critical resources for studying plant-virus biodiversity and epidemiology

Abstract

In the wake of a virus-mediated global health crises, research has rightfully focused on monitoring zoonotic viruses, particularly those that are emerging or novel in human populations (Baker et al., 2022). Viruses that infect plants are also worthy candidates for research investment and, depending on host outcomes, epidemiological action (Anderson et al., 2004; Jones and Naidu, 2019; Jones et al., 2021). While not all viruses are pathogenic (Roossinck, 2011; Takahashi et al., 2019), crop diseases caused by viral symbionts undermine food and economic security worldwide (Bos, 1982; Sastry and Zitter, 2014; Trębicki and Finlay, 2018; Rao and Reddy, 2020), and the consequences of viruses on plant biodiversity and ecosystems are understudied (Kamitani et al., 2016; Jones and Naidu, 2019; Lefeuvre et al., 2019). Better data regarding spatiotemporal patterns in plant-virus distributions is a prerequisite for understanding how viruses move, change, and emerge as threats to food and ecosystem security.

One way that temporal trends in virus biodiversity may be studied is through use of natural history collections (Cook et al., 2020; Thompson et al., 2021), which offer the opportunity to retrospectively characterize host–virus interactions, thus building a baseline to which contemporary analyses may be compared. Similarly, Cook et al. (2020) demonstrate the potential benefit of using historical host specimens to efficiently survey for virus diversity across taxa and environments. This work, like most specimen-based research into historical virus diversity, focused on animal hosts. Here we discuss opportunities that would arise from utilizing plant collections in a similar fashion; while the practical and technical details of isolating plant-associated viruses from historical tissue differ from methods for other taxonomic groups, the benefits to research and disease management would be similar and numerous.

There are multiple possible virus isolate types that may be useful in studying historical plant virus communities, including agricultural isolates and “forgotten” frozen tissue specimens collected by academic and agricultural researchers (Jones et al., 2021). We discuss pros and cons of using different tissue sources and conclude that usefulness of whole-host data from herbarium specimens justifies investment in development and research. Our objectives in this commentary are to (1) review and compare current resources and approaches available for studying plant-associated virus diversity in the context of natural history and (2) outline steps to improve global plant-virus biodiversity monitoring and preservation going forward.

Plant viruses are ubiquitous across host taxa and environments, but little is known regarding the history and biogeography of plant–virus interactions in wild plant communities. Herbaria are rich and opportune whole-host resources that may provide insight into fundamental questions about the mechanisms and consequences of plant–virus symbioses for theoretical and practical use. At this time, the principal requirement to make use of these vast biodiversity collections is the development of adequate methods to determine how feasible and biased reassembled virus communities are when isolated from pressed botanical specimens. Additionally, we advocate for new collections of atypical-looking plants and encourage subsampling of whole-plant specimens to preserve tissue in cryostorage or in silica. Finally, collaborative and transdisciplinary research teams working out of herbaria can provide important insight for the biosecurity of plant communities and crops across the planet, with opportunities to improve equitable coverage of data and resources going forward. Because viruses are global, so too are their hosts and humans who may study them; we anticipate an exciting, integrative future uncovering this universally understudied axis of plant biodiversity.

E.M.L. contributed to conceptualization, data acquisition and analyses, visual aid creation, manuscript writing, revision and editing. H.E.M. contributed to conceptualization, manuscript writing, revision, and editing.