Potential of rhizobial symbiosis as a biocontrol strategy against Ascochyta blight in pea.

 Abstract :

Pea is a legume crop of major agroecological interest, but its cultivation remains limited by the Ascochyta blight disease complex. Symbiotic interactions with beneficial microorganisms offer a promising strategy for biocontrol by enhancing plant defenses against pathogens. In particular, inoculation with rhizobia can prime pea defenses and enhance systemic resistance. My study aims to (i) characterize the molecular mechanisms underlying symbiotic defense priming and (ii) identify rhizobial strains that enhance this trait while maintaining high nitrogen-fixation efficiency We investigated the effects of pea seed inoculation with rhizobia on Ascochyta blight development in mature plants of four pea genotypes. Symbiosis significantly reduced disease symptoms in all four genotypes compared with non-inoculated controls. Leaf transcriptomic and metabolomic analyses revealed a conserved response across genotypes, characterized by the pre-activation of several defense-related pathways before pathogen infection, rather than a response induced only after infection. We identified transcripts and metabolites associated with this symbiotic primed state. The selection of elite rhizobial strains combining enhanced pea resistance to Ascochyta blight with high nitrogen-fixation efficiency is currently underway.