Variation in the structure of microbial communities associated with 1 different alfalfa (Medicago sativa L.) cultivars

Zhou Juan^1*hao Jia Li²Zhuo Shi Dang²Yan Xiao Zhao²Hua Mei Li²Dong Ying Gao²

• ¹Hetao College, Bayan Nur, China
• ²Ningxia University, Yinchuan, China

Abstract: The rhizosphere is a critical zone for root–soil–microbe interactions, and plant species play a 6 major role in shaping its microbial community structure. Alfalfa (Medicago sativa L.), a widely cultivated 7 forage crop with high nutritional and economic value, serves as an ideal model for studying cultivar-specific 8 rhizosphere microbiomes. Using high-throughput sequencing, this study analyzed the rhizosphere microbial 9 communities of seven alfalfa cultivars. A total of 27,878 bacterial OTUs and 5,380 fungal OTUs were 10 identified across all samples. The dominant microbial phyla included Actinobacteria and Proteobacteria 11 (bacteria) as well as Ascomycota (fungi). Although the overall microbial community composition was 12 broadly similar across cultivars, some subtle differences were observed. Key bacterial genera such as 13 Bacillus, Arthrobacter, Nocardioides, and Gaiella were abundant in the rhizosphere. Notably, the cultivars 14 'JN7' and 'QJ' exhibited higher overall microbial abundance than the other cultivars. Soil properties were 15 found to differentially influence microbial abundance across the cultivars. Specifically, soil organic matter, 16 total nitrogen (TN), and total phosphorus (TP) significantly affected bacterial abundance, while TP, TN, and 17 available phosphorus were the key drivers of fungal community variation. Network analysis revealed 18 stronger co-occurrence relationships among bacterial taxa than among fungal taxa, and predominantly 19 positive associations were detected. This study provides insights into alfalfa cultivar-associated rhizosphere 20 microbiomes and provides a foundation for the development of targeted biofertilizers and optimized 21 cultivation strategies.