Journal of Advances in Biology & Biotechnology

The increasing environmental concerns associated with excessive synthetic pesticide use and pathogen resistance have encouraged the investigation of sustainable approaches to plant disease management. Seaweed extracts are potential biostimulants because their bioactive constituents can influence plant growth and activate endogenous defence responses. This review examines the principal seaweed-derived components associated with disease resistance, particularly polysaccharides, alginates, laminarins, carrageenans, ulvans and phenolic compounds. It considers their roles in receptor-mediated signalling, reactive oxygen species generation, mitogen-activated protein kinase pathways and interactions among salicylic acid, jasmonic acid and ethylene. These processes may contribute to defence priming, the activation of antioxidant and defence-related enzymes, the accumulation of phenolics and phytoalexins, and the reinforcement of plant cell walls. Reported applications indicate potential activity against fungal, bacterial, viral and nematode pathogens, through direct antimicrobial effects or the induction of host resistance. However, treatment outcomes depend on seaweed species, extraction methods, chemical composition, formulation, application rate, crop genotype and environmental conditions. Commercially available formulations demonstrate opportunities for agricultural use, although inconsistent extract composition and limited field validation constrain broader application. Further chemical characterisation, standardisation of extraction procedures, crop-specific optimisation and integrated molecular investigations are needed to improve reproducibility. The available evidence supports the continued evaluation of seaweed-derived biostimulants as components of integrated plant disease-management strategies rather than as universally effective replacements for conventional treatments.