Tracking milestone advances in exploiting Rhizobia in biocontrol of plant diseases

Abstract

Rhizobia, long recognized for symbiotic nitrogen fixation, have recently emerged as promising biocontrol agents against a broad spectrum of soil-borne plant pathogens. This concise review summarizes milestone advances demonstrating how rhizobia suppress fungal, oomycete and nematode diseases in both legume and non-legume crops. Disease suppression is mediated through direct mechanisms such as siderophore-mediated iron competition, antibiosis and secretion of cell wall-degrading enzymes, as well as indirect mechanisms involving induced systemic resistance and modulation of plant defense signaling pathways. Emphasis is placed on molecular interactions, phytoalexin induction and quorum sensing as central processes underlying rhizobial biocontrol. Key challenges and future research priorities for integrating rhizobia into sustainable plant disease management strategies are highlighted.