ABSTRACT
Protecting plants from diseases generally requires a massive use of chemical compounds, such as fungicides. However, some of them cause unintended secondary effects such as occurrence of resistant strains and have an impact on environment and human health. In nature, plants are incessantly in contact with pathogenic microorganisms and, unlike mammals, lack mobile defender cells and an adaptive immune system. The innate ability of plants to detect pathogens is essential for their survival and thus they respond to attack with the activation of transcriptional and biochemical pathways that serve to prevent further damage by pathogens. Most macroalgal and derived polysaccharides activate plant defense responses and protection against a range of pathogens by activating salicylic acid, jasmonic acid and/or ethylene signaling pathways at a systemic. Alginates in extracts can induce oxidative burst in and the elicitor activity of the polymannuronic acid fraction from Chile increased the phenylalanine ammonia-lyase and peroxidase activities in wheat plants.
