Differential regulation of antioxidant machinery on grass pea partial resistance against powdery mildew and rust pathogens

Powdery mildew ( Erysiphe pisi , E. trifolii ) and rust ( Uromyces pisi ) are important diseases affecting grass pea ( Lathyrus sativus ). This study investigates grass pea's histological, enzymatic, and metabolic responses to these pathogens using accessions with contrasting resistance. Partially resistant (PR) accessions exhibited smaller fungal colonies from 48 h after inoculation (HAI) onwards. Enhanced superoxide dismutase (SOD) activity was observed as early as 12 HAI in PR accessions against both powdery mildews, associated with increased ascorbate peroxidase (APX) and catalase (CAT) activity in E. trifolii and E. pisi infections, respectively. Moreover, phenolic compounds and flavonoids accumulated in E. trifolii -infected PR accessions (6–48 HAI). For rust, APX activity rose at 48 HAI in PR accessions. These findings suggest that partial resistance (PR) in grass pea is characterized by restricted pathogen invasion and a dynamic regulation of reactive oxygen species (ROS)-scavenging enzymes, with responses varying across pathosystems. This highlights the importance of pathogen-specific selection strategies to minimize the risk of resistance breakdown and promote durable disease resistance in breeding programs. • Partially resistant (PR) accessions limited pathogen development at 48 h after infection. • Increased activity of APX and SOD in PR accessions infected with powdery mildews. • Phenolics and flavonoids accumulated in PR accessions infected with E. trifolii .