Arbuscular mycorrhizal fungus (AMF) establishes beneficial associations with most terrestrial plants and is known to enhance tolerance against salinity stress. However, the specific role of AMF-mediated soil enzyme activation and downstream signaling mechanisms in rice remains poorly understood. In this study, we investigated the effect of Claroideoglomus claroideum on soil enzyme dynamics (protease, sucrase, invertase, β-glucosidase, and urease) and their contribution to NaCl stress alleviation in two rice varieties. Rice seedlings were inoculated with AMF and exposed to 175 mM NaCl under controlled conditions. Mycorrhization significantly increased the activities of soil enzymes, with protease, urease, sucrase, invertase, and β-glucosidase enhanced by 60, 61, 70, 140, and 32%, respectively. Enhanced enzymatic activities promoted nutrient mobilization and root exudation, leading to higher accumulation of N-rich osmolytes such as proline and sugar-derived metabolites such as glucose. These compounds not only contributed to osmoprotection and secondary metabolite production (anthocyanins and flavonoids) but also supported microbial resilience in the rhizosphere. Importantly, AMF association triggered Ca2+ signaling events that strengthened antioxidant defenses, corroborated by increased Fe2+ uptake and elevated superoxide dismutase, catalase and peroxidase activities. Collectively, these mechanisms alleviated oxidative damage and improved physiological performance under NaCl stress. This study highlights the crucial role of AMF in linking soil enzyme activity with Ca2+ signaling and Fe-assisted antioxidant machinery, providing a sustainable biological strategy for mitigating salt stress in rice cultivation.
Joel et al. (Mon,) studied this question.