Establishment of plant lines cured of vertically transmitted 'good' viruses: The effects on plant growth and seed characteristics
Several pathogenic viruses benefit plants under specific circumstances, e.g., by inducing drought resistance. It is hypothesised that RNA viruses in the Endornaviridae and Partitiviridae families, sometimes called persistent since they are exclusively seed-transmitted at ~100% efficiency, have followed evolutionary trajectories towards mutualism. However, evidence comes from crossing non-identical host backgrounds making it impossible to distinguish definitively between the effects of viral versus host genotypes. We used virus-induced gene silencing (VIGS) to cure pepper plants of bell pepper endornavirus (BPEV) and the partitiviruses pepper cryptic virus 1 (PCV1) and PCV2 and compared these with genetically identical plants retaining these viruses. We found that PCV1, PCV2 and BPEV can significantly affect aerial and root growth and fruit/seed characteristics in ways that could benefit host fitness. VIGS-mediated curing allows unambiguous hypothesis-testing of potential benefits of persistent viruses and exploration of how viral and host genotypes shape persistent virus-host relationships.