From “Foliar application of supplemental IBA combined with ascorbic acid or quercetin to stimulate rooting in Kalamata and Wardan olive cuttings” by Rashedy, Kamil, Mohammed, Eldeeb and Hamed (Journal of Applied Horticulture, 2026).
The study evaluates whether foliar IBA, combined with ascorbic acid (ASC) or quercetin (QC), can improve rooting in two olive cultivars with contrasting rooting ability. The authors report that IBA alone had limited effect on Kalamata and a negative effect on Wardan, whereas ASC—either alone or combined with IBA—consistently enhanced rooting in both cultivars. QC showed cultivar‑dependent responses, stimulating rooting in Wardan but not in Kalamata.
Rooting improvements were closely associated with biochemical changes: increased catalase (CAT) and peroxidase (POD) activity, and reduced polyphenol oxidase (PPO) and indole‑3‑acetic acid oxidase (IAAox). ASC at 50 ppm produced the highest rooting percentages (12.1% in Kalamata and 54.4% in Wardan), coinciding with strong increases in CAT and POD and marked reductions in IAAox and PPO. These enzymatic shifts indicate enhanced antioxidant capacity and reduced auxin degradation, conditions favourable for adventitious root initiation.
QC enhanced rooting only in Wardan, aligning with previous findings that phenolic profiles differ between easy‑ and difficult‑to‑root cultivars. Its effect appears linked to its role as a substrate in POD‑mediated reactions that protect endogenous auxin from oxidation.
Overall, the authors conclude that ASC is a reliable enhancer of rooting in both cultivars, while QC is effective only in Wardan. The results highlight the importance of cultivar‑specific biochemical environments and suggest that foliar ASC, with or without IBA, is a practical strategy to improve propagation efficiency in difficult‑to‑root olive cultivars.