Effects of Elevated CO₂ on Bean Pod Mottle Virus Infection in Both Incompatible and Compatible Interactions With <i>Phaseolus vulgaris</i> L

Plant viruses cause significant crop losses, a situation that could worsen due to anthropogenic activities driving global climate change, one factor of which is the increase in atmospheric CO₂ concentration. This study assessed the impact of elevated CO₂ concentration (eCO₂, 1000 vs. 400 ppm) on two genotypes of common bean (Phaseolus vulgaris L.), one susceptible and one resistant, infected with bean pod mottle virus (BPMV, Comovirus siliquae). For both genotypes, we found that plant growth, development and physiology were not enhanced under eCO₂ enrichment in healthy plants, at the stage of BPMV inoculation. Under eCO₂, the number of primary infection sites was reduced in both genotypes. Consistently, viral titre in inoculated leaves was lower, suggesting an enhanced resistance to BPMV in both genotypes under eCO₂. To investigate the underlying mechanisms, we studied the expression of genes involved in different antiviral immune pathways: salicylic acid (SA)-signalling, RNA silencing and PAMP-triggered immunity (PTI) pathways. Under our experimental conditions, eCO₂ neither primed the SA-signalling pathway nor the PTI pathway, in both genotypes. However, eCO₂ seems to prime the RNA silencing pathway in the resistant genotype, and to a lesser extent, in the susceptible genotype.