Objective This study aimed to investigate the mutualistic symbiotic mechanism between arbuscular mycorrhizal fungi (AMF) communities from natural grasslands and Medicago sativa seedlings, providing a theoretical foundation for identifying suitable native high-quality microbial resources.

Method We collected two AMF community inoculants from temperate meadow steppe and typical steppe in Inner Mongolia of northern China and used microbial filtrates without AMF propagules as controls. Two M. sativa varieties, Beilin 201 and Zhongmu No.1, were inoculated with these AMF communities. By analyzing the symbiotic relationship between AMF community and M. sativa and their effects on seedling growth and nutrient absorption, we evaluated the symbiotic effect of AMF communities from natural grasslands on M. sativa seedlings.

Result (1) There were significant differences in composition and structure of AMF communities from different grassland types, and all communities successfully established symbiotic relationships with two varieties of M. sativa. Glomus and Claroideoglomus were dominant genera in inoculated root systems. (2) Compared with no inoculation, AMF inoculation significantly increased the aboveground biomass and phosphorus content in plant tissues of M. sativa, but significantly reduced the nitrogen content in plant tissues but reduced nitrogen content. Notably, plants inoculated with AMF from the typical steppe exhibited a significant negative effect on nitrogen uptake, resulting in a significant decrease in plant nitrogen-to-phosphorus ratio (P < 0.05). The mycorrhizal growth response, phosphorus uptake effect, and nitrogen uptake of Beilin 201 were significantly greater than those of Zhongmu No. 1. (3) The mycorrhizal phosphorus uptake response of Beilin 201 after inoculation showed a significant positive correlation with the diversity of AMF within the roots, whereas the mycorrhizal phosphorus uptake response of Zhongmu No.1 exhibited a significant negative correlation with AMF diversity (P < 0.05), which means that a diverse diversity of AMF community may be more conducive to phosphorus uptake by Beilin 201.

Conclusion The AMF community from natural grasslands can significantly promote the growth and phosphorus absorption of M. sativa seedlings, but this ecological function is influenced by characteristics of M. sativa varieties. The composition of AMF community plays a crucial role in determining these ecological functions. Therefore, when selecting native AMF community for inoculation, it is essential to consider the compatibility between plant varieties and AMF communities to maximize optimal production and ecological benefits.