Ulvan in Agriculture: An Eco-Friendly Approach to Plant Disease Management

Plant pathogens can result in massive crop destruction globally, thereby increasing starvation, while conventional or synthetic pesticides are harmful to the environment and human health. The urgent need for sustainable and eco-friendly disease management strategies has driven interest in natural biocontrol agents. Ulva sp. produce a sulfated polysaccharide named ulvan, which serves as a multifunctional biostimulant with pronounced antibacterial, antiviral, and antifungal properties against a broad spectrum of phytopathogens. Its complex anionic structure plays a dual role by directly inhibiting pathogen growth through cell membrane disruption and biofilm suppression, while simultaneously inducing plant defense mechanisms through reactive oxygen species (ROS) signaling and activation of pathogenesis-related (PR) proteins. Recent advances in ulvan extraction, purification, structural analysis, and inhibitory mechanisms of phytopathogens are discussed in this review. Furthermore, the biodegradability and biocompatibility of ulvan highlight its potential applications beyond agriculture, including biomedical and sustainable biomaterial development. By comprehensively analyzing the bioactivity spectrum and mechanistic pathways of ulvan, this review proposes strategic approaches for integrating ulvan into environmentally friendly plant disease management systems, supporting its role in advancing a circular bioeconomy.