Carbohydrate Oxidase Gene Expression in Sunflower During Orobanche Cumana Infection

Carbohydrate oxidases (SCO) represent a class of enzymes involved in carbohydrate metabolism and in the generation of hydrogen peroxide (H₂O₂), a key molecule in redox signaling and in the activation of plant defense responses. In this study, the transcriptional responses of the SCO gene were analyzed in three sunflower genotypes exhibiting contrasting reactions to O. cumana infestation, using a controlled artificial infestation system. The resulting expression profiles were correlated with the resistance or susceptibility phenotypes of the analyzed genotypes. The results revealed significant transcriptional differences among genotypes. Resistant genotypes showed an early and tightly regulated induction of SCO expression during the pre-attachment phase, followed by moderate and sustained activation associated with effective restriction of parasite establishment. In contrast, the susceptible genotype Performer exhibited a delayed and unbalanced response, insufficient to prevent successful infestation.