Intéractions plante-virus sous déficit hydrique

Plants suffer from a broad range of abiotic and biotic stresses that do not occur in isolation but are commonly present simultaneously. Productivity of natural and agricultural systems is frequently constrained by water limitation and the frequency and duration of drought periods should increase due to global climate change. In addition, phytoviruses represent highly prevalent biotic constraints in wild and cultivated species. Several clues support a modification of epidemiological parameters of plant viruses in response to environmental changes but a clear quantification of plant-virus interactions under abiotic stresses is still lacking. We assessed the effects of a severe water deficit on epidemiological parameters (virulence, viral load and transmission rate) and systemic spread of the Cauliflower mosaic virus, a non-circulativevirus, in a panel of natural accessions of Arabidopsis thaliana with contrasted morpho-physiological responses to water deficit. Plant growth-related traits, fitness and virus epidemiological parameters were evaluated in PHENOPSIS, an automated high-throughput phenotyping platform. Preliminary results on 9 accessions of A. thaliana show that water deficit had contrasted effects on CaMV transmission rate and viral load among A. thaliana accessions. Under well-watered conditions, transmission rate tended to increase with viral load and the sensitivity of the accession to CaMV. Under water deficit, transmission rate and sensitivity were negatively correlated while transmission rate and viral load remained positively correlated. Changes in the rate of transmission under water deficit were therefore not related to changes in viral load. Our results support the idea that optimal virulence of a given virus, as hypothesized under the transmission-virulence trade-off, is highly dependent on the environment and the physiology of the host. This suggests too that viruses may be able to intercept the stress signals of the plant and use them to their advantage (Bergès et al., 2018).