Valorization of Sugar Beet Byproducts into Oligogalacturonides with Protective Activity against Wheat Powdery Mildew

The shift toward sustainable agriculture emphasizes the need for eco-friendly biocontrol strategies. Oligogalacturonides (OGs), which are pectin-derived cell wall fragments, are promising plant defense inducers. This study evaluated two OGs mixtures, obtained from sugar beet byproducts, for their protective effect against Blumeria graminis f. sp. tritici (Bgt), the causal agent of wheat powdery mildew. OGs were generated by hydrolyzing pectins with two Arabidopsis thaliana polygalacturonases, ADPG2 and PGLR, expressed in Pichia pastoris. OGs-ADPG2 showed a degree of polymerization (DP) 1-10 and esterification (DE) 41%, while OGs-PGLR had DP 1-16 and DE 34.5%. Although neither inhibited Bgt spore germination directly, OGs-PGLR provided 31% preventive protection. Both OGs activated defense-related genes, but only OGs-PGLR induced lipoxygenase (9-LOX), initiating the octadecanoic pathway and oxylipin production. Overall, these results highlight the potential of OGs derived from sugar beet byproducts as sustainable alternatives to reduce phytochemical use in crop protection.