Effects of Elevated CO2 on Bean Pod Mottle Virus Infection in Both Incompatible and Compatible Interactions With Phaseolus vulgaris 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.