Endophytic seed microorganisms in legumes: Natural bioinoculants for sustainable agriculture

As global food demand rises against the backdrop of environmental and health concerns from intensive agrochemical use, there is an urgent need for sustainable crop-management strategies. In this perspective, seed-borne endophytic microbes, including bacteria and fungi, in legumes offer a naturally inherited bioinoculant system. This review integrates 35 Scopus and Web of Science studies to examine the occurrence, transmission dynamics, and functional diversity of endophytes within seeds of key legume species. Seed endophytes contribute to plant development and productivity through multiple mechanisms: atmospheric nitrogen fixation; solubilization of phosphorus and potassium; synthesis of siderophores and indole-3-acetic acid; and modulation of rhizosphere microbial communities, collectively enhancing germination rate, biomass accumulation, and yield. Under abiotic stress conditions, such as drought, nutrient deficiency, or contaminant exposure (metals and pesticides), such beneficial microbes promote root architecture remodeling, exopolysaccharide secretion, and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, thereby improving stress resilience. In biotic contexts, certain bacterial endophytes may contribute to biocontrol through antibiotic production, while fungal inoculants have been reported to synthesize alkaloids that can deter herbivores. By elucidating the multifaceted roles of legume seed endophytes, this review underscores their potential as a turnkey, eco-friendly bioinoculants, paving the way for greener agricultural practices without compromising crop performance.