CHITOSAN-BASED SEED COATING: A MULTIFUNCTIONAL PLATFORM FOR SEED ENHANCEMENT, STRESS RESILIENCE AND BIOTIC PROTECTION

Abstract

Chitosan-based seed coating is gaining attention as a biodegradable approach for integrating seed enhancement, stress tolerance and biological protection within a single treatment system. This review critically examines the role of chitosan in seed coating and related seed-treatment applications, with emphasis on germination and seedling establishment, root development, abiotic stress tolerance, pathogen suppression, insect pest management, defence activation and compatibility with beneficial microorganisms. Evidence from direct coating studies indicates that appropriately formulated chitosan can improve germination, seedling growth, antioxidant defence, membrane stability and in selected crops, yield. Complementary evidence from seed priming, soaking and other seed treatments further demonstrates potential for improving tolerance to salinity, drought and osmotic stress. The multifunctional effects of chitosan are associated with its film-forming capacity, cationic nature, antimicrobial activity and ability to elicit plant defence responses. Enhanced antioxidant and defence-related enzyme activities, reduced oxidative damage, improved ion homeostasis and maintenance of membrane integrity provide physiological evidence for these responses. However, chitosan performance is highly dependent on molecular weight, degree of deacetylation, concentration, formulation pH, coating thickness, additives, seed characteristics and environmental conditions. Excessive coating concentrations may restrict hydration and gas exchange, while unsuitable formulations can adversely affect germination or beneficial microbial viability. Although field studies have demonstrated improvements in crop performance and yield, field-scale evidence remains limited, particularly for formulation-specific coating systems. A critical distinction between true seed coating and other seed-treatment methods is therefore essential when interpreting the available evidence. Future research should focus on standardized characterization of chitosan, quantitative evaluation of coating properties and coating load, mechanistic understanding, formulation optimization, microbial compatibility, field validation, and assessment of scalability and economic feasibility. Overall, chitosan-based seed coating represents a promising multifunctional platform for sustainable seed management, but its broader agricultural application requires formulation-specific optimization and stronger field-based validation.