## 4 Conclusions  
In the current work, alignates, LMW alginate derivatives, ticoidans from the brown seaweed _S. muticum_ and _C. myriophyloides_, and the glycoproteins isolated from _C. decorticatum_ were characterized chemically and structurally. These saccharide extracts were investigated for their ability to induce the PAL and TAL activities, polyphenol, and lignin contents in the leaves of the olive tree (Picholine Marocaine). Sulfated polysaccharides (FUCCM, AGB, and AGP) were found to be the most active at a low concentration (0.5 g/L) compared to alignates (unsulfated polysaccharides), indicating the main role of the sulfate group in the efficiency of the elicitor activity. Fucoidan, with an M\({}_{\text{w}}\) of 148 kDa and 12.83% of sulfates was more effective than the other polymer fractions. The activity of alginate polymers and their derivatives was related to their concentrations and chain length. When compared to ALSM (202 kDa), the low molecular weight alignates OASM (3 kDa), ALCM (76 kDa), and OACM (19 kDa) were more efficient in inducing PAL and TAL activities at low concentrations. In addition, oligoalginates (OASM) manifested the highest levels at 2 g/L. PAL/TAL ratios were \(<\) to 1, indicating that the TAL enzyme was highly expressed in the leaves of the olive tree in response to all saccharide fractions except for ticoidan. The expression of the TAL enzyme in olive tree leaf tissue was examined for the first time. These results highlight the use of alignates, LMW alignates, ticoidan, and glycoprotein from marine macroalgae, as inducers of natural defenses of the olive tree, to protect against phytopathogens in the context of sustainable development. However, future research should consider the protective effects of these molecules against biotic and abiotic stresses under field conditions. Conceptualization, M.A., Z.E.A.-T., C.D. and C.E.M. ; methodology, M.A., Z.E.A.-T., C.D., M.T. and C.E.M. ; software, M.A. ; validation, M.A., Z.E.A.-T., C.D. and C.E.M. ; formal analysis, M.A., Z.E.A.-T., C.D. and C.E.M. ; investigation, M.A., Z.E.A.-T., C.D. and C.E.M. ; resources, M.A., Z.B., M.D.O.E.-H. and H.R. ; data curation, M.A. ; writing--original draft preparation, M.A. ; writing--review and editing, M.A., Z.E.A.-T., C.D., C.E.M., G.P., P.D. and P.M.; visualization, M.A., Z.E.A.-T., C.D., I.F., S.A. and C.E.M. ; supervision, Z.E.A.-T., C.D. and C.E.M. ; project administration, G.P. All authors have read and agreed to the published version of the manuscript. This work was funded by the French Ministry of Europe and Foreign Affairs and the Moroccan, Algerian, and Tunisian Ministries of Higher Education and Scientific Research, within the framework of the [PERSON] program (PHC Maghreb), grant number 19 MAG36, and by the National Centre for Scientific and Technical Research (CNRST Morocco), grant number 4 UCA2018. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: Not applicable. Acknowledgments: We want to thank [PERSON] and [PERSON] from Universite de Rouen Normandie (INSA Rouen) for SEC-MALLS analysis. Conflicts of Interest: The authors declare no conflict of interest. References  
[PERSON]; [PERSON] [PERSON] Verticillium wilt of olive: A case study to implement an integrated strategy to control a soil-borne pathogen. Plant Soil**2010**, 344, 1-50. [CrossRef]  
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