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

Meriem Aitouguinane,Pascal Dubessay,Soukaina Bouissil,Imen Fendri,Philippe Michaud,Zakaria Boual,Cédric Delattre,Zainab El Alaoui-Talibi,Cherkaoui El Modafar,Christine Gardarin,Halima Rchid,Anouar Mouhoub,Guillaume Pierre,Mohamed Didi Ould El-Hadj,Slim Abdelkafi

doi:10.3390/md18100521

Abstract

Polysaccharides extracted from marine algae have attracted much attention due to their biotechnological applications, including therapeutics, cosmetics, and mainly in agriculture and horticulture as biostimulants, biofertilizers, and stimulators of the natural defenses of plants. This study aimed to evaluate the ability of alginate isolated from Bifurcaria bifurcata from the Moroccan coast and oligoalginates derivatives to stimulate the natural defenses of tomato seedlings. Elicitation was carried out by the internodal injection of bioelicitor solutions. The elicitor capacities were evaluated by monitoring the activity of phenylalanine ammonia-lyase (PAL) as well as polyphenols content in the leaves located above the elicitation site for 5 days. Alginate and oligoalginates treatments triggered plant defense responses, which showed their capacity to significantly induce the PAL activity and phenolic compounds accumulation in the leaves of tomato seedlings. Elicitation by alginates and oligoalginates showed an intensive induction of PAL activity, increasing from 12 h of treatment and remaining at high levels throughout the period of treatment. The amount of polyphenols in the leaves was increased rapidly and strongly from 12 h of elicitation by both saccharide solutions, representing peaks value after 24 h of application. Oligoalginates exhibited an effective elicitor capacity in polyphenols accumulation compared to alginate polymers. The alginate and oligosaccharides derivatives revealed a similar elicitor capacity in PAL activity whereas the accumulation of phenolic compounds showed a differential effect. Polysaccharides extracted from the brown seaweed Bifurcaria bifurcate and oligosaccharides derivatives induced significantly the phenylpropanoid metabolism in tomato seedlings. These results contribute to the valorization of marine biomass as a potential bioresource for plant protection against phytopathogens in the context of eco-sustainable green technology.

Highlights

Today, pesticides are among the most widely used substances in agriculture worldwide to control losses caused by phytopathogens
Oligoalginates were obtained after radical depolymerization of the alginate by aqueous hydrogen peroxide (H2 O2 ) solution for 6 h at 70 ◦ C
The results presented by Abouraïcha et al reported that the phenylalanine ammonia-lyase (PAL) activity oligoulvans which strongly reduced wilting and mortality of tomato plants, by 44% and 54%, and phenolics content have been greatly enhanced in the apple fruit after elicitation by ulvan and respectively, compared to the control plants [6]

Summary

Introduction

Pesticides are among the most widely used substances in agriculture worldwide to control losses caused by phytopathogens. The increasing thrust toward the development of sustainable agriculture and green revolution technologies has led to the emergence of new molecules derived from natural sources, biopesticides Despite their non-toxic mechanisms and eco-friendly manner, their usefulness is increasingly restricted because of their expensive cost of production, the broad spectrum, which might lead to negative effects on non-target organisms, and low reliability due to low stability [2]. In this context, new promising alternative approaches were developed by researchers, one of them, the stimulation of the natural plant defenses using natural elicitors that does not exert selective effects on the pathogen. This strategy aims to induce plant resistance against a broad spectrum of microorganisms [3]

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