Abstract: Plant roots recruit enormous diverse microorganisms from the complex soil environment to construct rhizosphere microbial communities, which is beneficial to plant health. In this study, we collected rhizosphere and non-rhizosphere soil samples during the budding period, flowering period, and fruiting period of walnut. The high-throughput sequencing and the subsequent analysis of differential species and function, and microbial ecological network correlation were performed to characterize rhizosphere microbial communities during different growth periods. Results showed that there was difference in the dominant microorganisms dwelling in the walnut rhizosphere during different growth periods. The relative abundance of Bacillus and unclassified Fungi significantly increased during the budding period; unclassified Chloroplast, Cladosporium, Alternaria and Acaulium significantly increased during the flowering period; unclassified Micrococcaceae, Pseudomonas, Streptomyces, Gibberella and Mortierella significantly increased during the fruiting period. Among them, Bacillus (with a relative abundance of 3.0%), unclassified Chloroplast (4.5%) and Pseudomonas (17.9%) were the dominant beneficial genera in the rhizosphere soil during the budding period, flowering period, and fruiting period, respectively. The structure of rhizosphere microbial communities significantly differed during different growth periods (P<0.05). The results of topological features analysis showed that, compared to the non-rhizosphere soil, the microbial ecological network in the rhizosphere soil showed stronger, more complex, and tighter correlations. The network complexity of bacterial and fungal communities was the highest during fruiting period and budding period, respectively, while the positive correlation was the highest during the budding period and fruiting period, respectively. This study provided a theoretical basis for the collection of soil samples and the screening of beneficial bacteria for walnut growth promotion and biocontrol.

Key words: Juglans regia L., growth period, rhizosphere microorganism, high-throughput sequencing, differential species analysis, microbial ecological network.