Contrasting metabolic responses of two chickpea varieties to root infection by Phytophthora are influenced by arbuscular mycorrhizal inoculation

Most terrestrial plants, including important crop plants like chickpea (Cicer arietinum), benefit from mutualistic symbiosis with arbuscular mycorrhizal (AM) fungi due to enhanced nutrition and improved immune responses. Although this latter phenomenon, so-called Mycorrhiza Induced Resistance (MIR), is well-reported and metabolic adjustments have been observed, the diversity of mechanisms by which AM fungi prime disease resistance are still poorly understood. Using two chickpea varieties (Sonali and Kyabra) we investigated how differential host genotypes may impact AM-mediated defence responses against a root rot pathogen, Phytophthora medicaginis. Inoculation with Rhizophagus irregularis significantly inhibited disease-related biomass losses in Kyabra, while no impact on plant biomass was observed in Sonali. Using root metabolomic profiling, we detected 143 metabolic features which exhibited significant variation between at least two experimental conditions. Most noteable, the two chickpea varieties tested largely showed opposing metabolomic responses to microbial exposure. Furthermore, co-innoculation of pathogenic and beneficial microbes led to a core set of differentially expressed metabolomic features in Kyabra and Sonali. These results demonstrate contrasting levels of metabolomic responses to microbial inoculation and reveal potential molecular features involved in MIR in a globally relevant crop.