• Oxidative pre-planting treatments modulate early establishment of onion sets. • HOCl and aqueous ozone act as dual-function disinfectant–elicitor agents in onion sets. • APX-driven redox homeostasis supports coordinated establishment and early development. • Strong oxidative treatments trigger CAT responses associated with growth penalties. • HOCl and aqueous ozone outperform Cu-based disinfection by preserving early growth. Onion sets ( Allium cepa small dried bulblets) are widely used for summer cultivation in Mediterranean regions, where direct seeding is unfeasible due to extreme conditions. However, bulblet production and storage often increase microbial contamination and lead to non-uniform sprouting, affecting early crop establishment. This study provides the first systematic evaluation of oxidative sanitizers in onion sets, assessing their dual role as microbial disinfectants and physiological elicitors under controlled conditions. The tested compounds -hypochlorous acid (HOCl), hydrogen peroxide (PEROX), and ozone (aqueous and gaseous)- were compared to a conventional copper-based treatment. We assessed their impact on microbial load, rooting and sprouting, seedling growth, oxidative damage (H₂O₂ accumulation, lipid peroxidation) and antioxidant responses (catalase, ascorbate peroxidase, soluble sugars and total antioxidant capacity). HOCl-treated bulbs showed reduced oxidative damage and increased antioxidant activity, which coincided with improved rooting (11 %), and sprouting (33 %) and greater uniformity during early development. Aqueous ozone also enhanced sprouting (∼30 %) and stimulated antioxidant responses although its bulb disinfection efficiency was lower, despite reducing soil bacterial content. In contrast, H₂O₂ and gaseous ozone were effective disinfectants but induced oxidative stress, resulting in reduced root growth and lower seedling performance. Principal Component Analysis revealed that HOCl and aqueous ozone clustered with APX activity and increased DPPH scavenging capacity, associated with more favourable early establishment, while H 2 O 2 and Cu-base treatments were associated to sugar accumulation and CAT activity. Overall, oxidative sanitizers such as HOCl and aqueous ozone may act as physiological elicitors that improve early development, beyond their disinfection effect. These findings support their potential as sustainable alternatives in onion set cultivation, with possible applications for improving early establishment while contributing to soil health.
Bárzana et al. (Sun,) studied this question.