Biostimulants: The First Line of Defense Against Plant Diseases

Abstract

Abstract

AbstractBiostimulants are natural substances or microorganisms that stimulate plant physiological processes. Unlike fertilizers, they do not supply nutrients directly but enhance nutrient uptake, stress tolerance, and plant immunity. Key benefits include: enhanced root growth and efficiency, improved tolerance to salinity, drought, heat and cold, increased photosynthesis and chlorophyll content, activation of systemic acquired resistance SAR and PR proteins against pathogens, and improved soil properties with reduced chemical inputs. Main types include: Microbial biostimulants such as Trichoderma fungi that parasitize pathogens and produce chitinase enzymes, and PGPR bacteria like Bacillus and Lysinibacillus that fix nitrogen, solubilize phosphorus, produce antibiotics and siderophores. Non-microbial biostimulants include seaweed extracts, amino acids, humic and fulvic acids for soil and root improvement, and salicylic acid for immunity activation and delaying senescence. In conclusion, biostimulants act through direct antagonism of pathogens and by strengthening plant defense systems. They offer a sustainable solution to reduce pesticides and fertilizers, especially under abiotic stress conditions.