Controlling plant diseases is essential to the long-term viability of agriculture. As the most significant global agricultural liability, fungal phytopathogens infect a widespread array of host plants and epitomize a substantial menace to plant species. The use of bioproducts, including extract seaweed, is one potential lever to encourage this transition. Alginates, alginate oligosaccharide, laminarins, ulvans, phenols, and carrageneans are seaweed metabolites and chemicals that have been shown to have direct antifungal properties. These substances limit the growth of the fungi by breaking down their cell walls and causing oxidative stress. This provides considerable disease control in plants at an early stage and substantially lowers the incidence of disease. It is believed that by starting a cross-talk between the defense pathway and phytohormone, seaweed oligosaccharides and ulvans stimulate synthesis of plant protective compounds as well as physiological changes that prevent pathogen entry like lignification or accumulate cell wall degrading enzymes (chitinase or glucanase) or antimicrobial compounds (phenols, salicylic acid) at the sites of infection. This activates the ethylene, jasmonic, and salicylic acid pathways, which in turn increases the synthesis of several plant defense chemicals and activates pathogenesis-related genes (PR 1–3). Effective disease management has been facilitated by increased oxidative enzyme production to avoid oxidative stress induced by pathogen entry also.
Taking cannabis cultivation as an example, compounds such as polyphenols, terpenes, and chitinases not only directly inhibit the growth and reproduction of pathogens but also induce systemic acquired resistance (SAR) in cannabis plants, enabling them to more quickly activate defense mechanisms when attacked by pathogens, reducing the likelihood of disease. The brown algae polyphenols in seaweed possess strong antimicrobial activity, effectively inhibiting the pathogens that cause cannabis root rot. Terpenes, on the other hand, can volatilize to form a chemical barrier around the plant, deterring pests and pathogens. Furthermore, certain oligosaccharides in seaweed extracts act as signaling molecules, triggering the expression of defense genes within cannabis cells and increasing the production of phytoalexins and pathogenesis-related proteins, further enhancing the plant’s overall disease resistance.
This dual defense mechanism, mediated by natural seaweed extract, not only enhances cannabis’s resistance to biotic stress but also works synergistically with the antioxidant system to ensure healthy growth in complex environmental conditions, providing comprehensive protection for high-quality and high-yield cannabis.
In short, rather than a single mechanism for disease control, seaweed compounds instigate a cascade of reactions that activate plant defense offering multifold resistance and protection against phytopathogenic fungi. Organic seaweed extract for plants such as Dora KelpReal and AlgaNeo are examples of such seaweed biostimulants. These seaweed extract fertilizer products significantly promote a benign environment for plant growth, positively impacting the nutritional status and yield of plant products in an economical and sustainable manner.
