TOMATO SEED PRIMING WITH WATER-SOLUBLE POLYSACCHARIDES FROM JANIA ADHAERENS PROMOTES PLANT GROWTH AND INCREASES PLANT RESISTANCE TO SOILBORNE PATHOGENS

Marine macroalgae are a source of natural bioactive compounds, such as polysaccharides, that deserve exploitation in the field of plant disease management. Moreover, current European regulations require that priority should be given to alternative products than synthetic pesticides. In agriculture, algae have been mostly used for their beneficial properties on plant development. In this study, we showed that tomato seed biopriming with water-soluble polysaccharides (WSPs) from the alga Jania adhaerens protects seedlings and adult plants from the soilborne pathogens Fusarium oxysporum f.sp. lycopersici, Pythium ultimum and Rhizoctonia solani artificially inoculated in a growing substrate. First, WSPs were characterized by FT-IR spectroscopy and seedling emergence, disease severity, and expression of genes related to phenylpropanoid, chlorogenic acid, SAR and ISR pathways, and chitinase and β-1,3 glucanase activities were investigated after seed priming. WSPs FT-IR spectra showed typical bands assigned to alduronic acids and glycosidic linkage formation in polysaccharides. Depending on the WSPs dose, seed treatment enhanced seedling emergence, reduced disease severity and increased plant growth. Moreover, HQT, HCT, PAL, PR1 and PR2 genes were significantly upregulated together with β-1,3 glucanase activity. These results show that algal WSPs have the potential for being considered as natural compounds for soilborne pathogens control in sustainable agriculture.