Marine algae oligosaccharides: Eco-friendly elicitors for sustainable agriculture

Abstract

With an increasing demand for agricultural production to meet global needs, the emphasis is on enhancing crop yields over expansion on arable farming lands. Traditional methods to combat plant diseases involving fungicides, bactericides, and insecticides have raised concerns due to their adverse effects on health and the environment. Consequently, there is an urgent need for novel and environmentally friendly approaches to control plant diseases. Elicitors are defined as substances that stimulate the production of specific bioactive components. These compounds, when applied in small quantities, activate plant defense mechanisms. Seaweeds, classified into three major groups, play crucial roles in marine ecosystems and have great economic significance. Among the aquatic flora, these marine algae are especially notable for their high content of marine algae polysaccharides (MAP), including carrageenan, alginate, fucoidan, laminaran, agarose and ulvan that have been reported to act as elicitors of plant defenses. When hydrolyzed, MAPs yield marine algae oligosaccharides (MAOs), which garnered more significant interest in recent years because of their superior solubility. This review presents a holistic view of seaweeds as natural elicitors, primarily focusing on MAPs and MAOs in enhancing the defensive capabilities of plants. We discuss various methodologies deployed to process MAOs from MAPs, and provide a comprehensive comparison of their efficacies. Further, we explore their application regimens of as elicitors for plant defense, particularly in the context of sustainable agriculture.