Use of Alginate Extracted from Moroccan Brown Algae to Stimulate Natural Defense in Date Palm Roots

Abstract

Our study aimed to search for seaweed polysaccharides able to stimulate date palm defense mechanisms. Extraction, purification, characterization, and elicitor activity of sodium alginate (FSSA and BBSA) from Moroccan brown seaweeds Fucus spiralis and Bifurcaria bifurcata were investigated. FSSA and BBSA were characterized by proton nuclear magnetic resonance spectroscopy (1H-NMR) and size exclusion chromatography (HPLC-SEC). The mannuronic acid/guluronic acid (M/G) ratio of FSSA was M/G = 0.92 indicating that FSSA contained 48% and 52% of mannuronic and guluronic acids respectively, and the M/G ratio of BBSA was 0.47 indicating that BBSA contained 32% and 68% of mannuronic and guluronic acids respectively. Elicitor activity of FSSA and BBSA was carried out by developing an innovative study model on the date palm. The elicitor capacities were evaluated by investigating phenolic metabolism including phenylalanine ammonia-lyase (PAL) activity and total polyphenol content in seedling roots of date palm maintained in alginates solution (FSSA and BBSA) at different concentrations. The results obtained show that the PAL activity and the phenolic compound content were significantly stimulated with 1 mg·mL−1 of FSSA and BBSA; after 1 day of treatment with FSSA, and after 12 h of treatment with BBSA. These results show clearly those alginates extracted from Moroccan brown algae induced in date palm roots the stimulation of natural defense mechanisms.

Induction of Natural Defenses in Tomato Seedlings by Using Alginate and Oligoalginates Derivatives Extracted from Moroccan Brown Algae

“…These studies revealed clearly, the capacity of alginates, extracted from the brown seaweed Bifurcaria bifurcata , and oligoalginates derivatives to induce PAL activity ( Figure 1 ) and polyphenols biosynthesis ( Figure 2 ) in the leaves of tomato seedlings. Based on these results, and on previous study realized on date palms using the same alginates [ 12 ], we suggest that polysaccharides isolated from Bifurcaria bifurcata and their oligomers could be important elicitors to trigger the natural defenses of different plants enhancing protection against a wide range of phytopathogens. Additional studies are therefore required for exploring the protective effects of these molecules.…”

“…Extraction and purification techniques were potentially optimized to achieve higher yield of target compound. As described in the previous study [ 12 ], the yield of alginate was about 24% ( w/w ), and the chemical composition was revealed as 48.6% of total sugars, with the abundance of uronic acids (58.4%), and the presence of minor impurities (phenolic compounds, proteins, and sulfate groups). Total carbohydrates were determined by the Dubois method [ 13 ].…”

“…Alginate was extracted from the brown seaweed Bifurcaria bifurcata from the Moroccan coast. The polysaccharides were extracted through a series of steps involving acid and alkali heat treatment and purified by rinsing several times with ethanol, and then analyzed chemically and structurally [ 11 , 12 ]. Oligoalginates were obtained after radical depolymerization of the alginate by aqueous hydrogen peroxide (H 2 O 2 ) solution for 6 h at 70 °C.…”

“…The estimated M/G ratio from 1 H-NMR spectra shows higher values of guluronic acid (68%) than mannuronic acid blocks (32%, M/G < 1), indicating that the samples are rich in guluronic acid. All structural and chemical analyses of alginate were presented in the previous study with a detailed description [ 12 ]. The determination of the composition of alginates and their physical properties is an important criterion for knowing the gelling properties in order to select the appropriate concentrations for biological tests.…”

“…The polysaccharides and oligosaccharides used in this study were provided in the Institut Pascal, University Clermont Auvergne in France. The extraction and purification of alginate and oligoalginates derivatives, from the brown algae Bifurcaria bifurcata , were previously described in detail [ 11 , 12 ], and the Chemical Analysis, High-Performance Steric Exclusion Chromatography (HPSEC) (Agilent Technologies, Santa Clara, CA, USA) and NMR Spectroscopy Analysis (Bruker Scientific Instruments, Billerica, MA, USA), were established according to the published protocol.…”