Effects of Introduced and Indigenous Viruses on Native Plants: Exploring Their Disease Causing Potential at the Agro-Ecological Interface

Abstract

The ever increasing movement of viruses around the world poses a major threat to plants growing in cultivated and natural ecosystems. Both generalist and specialist viruses move via trade in plants and plant products. Their potential to damage cultivated plants is well understood, but little attention has been given to the threat such viruses pose to plant biodiversity. To address this, we studied their impact, and that of indigenous viruses, on native plants from a global biodiversity hot spot in an isolated region where agriculture is very recent (<185 years), making it possible to distinguish between introduced and indigenous viruses readily. To establish their potential to cause severe or mild systemic symptoms in different native plant species, we used introduced generalist and specialist viruses, and indigenous viruses, to inoculate plants of 15 native species belonging to eight families. We also measured resulting losses in biomass and reproductive ability for some host–virus combinations. In addition, we sampled native plants growing over a wide area to increase knowledge of natural infection with introduced viruses. The results suggest that generalist introduced viruses and indigenous viruses from other hosts pose a greater potential threat than introduced specialist viruses to populations of native plants encountered for the first time. Some introduced generalist viruses infected plants in more families than others and so pose a greater potential threat to biodiversity. The indigenous viruses tested were often surprisingly virulent when they infected native plant species they were not adapted to. These results are relevant to managing virus disease in new encounter scenarios at the agro-ecological interface between managed and natural vegetation, and within other disturbed natural vegetation situations. They are also relevant for establishing conservation policies for endangered plant species and avoiding spread of damaging viruses to undisturbed natural vegetation beyond the agro-ecological interface.

Mixed Infections of Four Viruses, the Incidence and Phylogenetic Relationships of Sweet Potato Chlorotic Fleck Virus (Betaflexiviridae) Isolates in Wild Species and Sweetpotatoes in Uganda and Evidence of Distinct Isolates in East Africa

“…Therefore, the most probable explanation of our observed low incidences of mixed infections may be inefficient vector transmission of viruses between the wild plants or between cultivated and wild plants [31] and/or high levels of virus resistance in wild species preventing infection or keeping virus titers at undetectable levels [12, 82]. Furthermore, synergistic or additive effects of multiple virus infections causing severe disease could have eliminated co-infected plants [1–2, 5, 83–86]. These effects can vary among populations [12, 87, 88], species [89] and environments [75, 90, 91].…”

“…Although virus-like symptoms were observed, no characteristic symptoms could be associated with a particular virus for several reasons, including mixed infections and condition of the host. Furthermore, many SPCFV- and SPCSV-infected wild plants remained symptomless, which seems common among wild plants [5, 8, 13, 18, 89, 97]. In addition, some symptom-expressing plants tested negative for SPCFV, SPCSV, SPMMV and SPFMV, indicating possible infection with other viruses that could not be detected with the antibodies and PCR primers used due to assay specificities.…”

Non‐cultivated grass hosts of yellow dwarf viruses in Ethiopia and their epidemiological consequences on cultivated cereals

“…Besides its direct effect on yield and yield components of host plants, researches have recently disclosed that generalist viruses such as the YDV complex can alter plant community dynamics via processes such as apparent competition, in which a plant host population negatively impacts another by indirectly increasing pathogen pressure on the second plant host population (Malmstrom et al., ). Viral infection on one species in a mixed plant species population of host and non‐hosts affected competitive ability sufficiently to alter plant species composition (Vincent, Coutts, & Jones, ). Borer et al.…”

Overlooking the smallest matter: viruses impact biological invasions

“…Viruses can cause infection with only subtle symptoms that may not be readily identifiable to invasion ecologists encountering them in wild populations. For example, in the Southwest Australian Floristic Region, a biodiversity hotspot where nearly 50% of plant species are endemic, virus symptoms on native plant foliage were incorrectly attributed to nutrient deficiencies for more than 50 years (Vincent et al 2014). Even when viral pathogens circulate in host populations at low levels before causing detectable outbreaks, as may be the case for viruses exposed to the novel host communities of invaded systems, they can be adapting to maximise fitness in the novel host (Longdon et al 2014).…”