Effect of long-term sugar beet cultivation on rhizosphere bacterial diversity, community structure and sugar yield of sugar beet

Long-term sugar beet cultivation in the black soil region of China not only affected sugar beet yield but also influenced rhizosphere soil bacteria. However, the relationship between sugar beet growth and rhizosphere soil bacteria is still indeterminate. Therefore, this study analyzed the sugar beet growth status, rhizosphere soil bacterial diversity, species, and functional composition of long-term cultivation fields (LCF) and initial planting fields (IPF) of sugar beet. The results showed that sugar beet leaf disease in the long-term cultivation fields was significantly aggravated and the sugar beet yield was significantly reduced compared with the initial planting fields. The content of available phosphorus in sugar beet rhizosphere soil and the diversity of the rhizosphere bacterial community were significantly decreased. The Proteobacteria and Actinobacteria were increased, while Acidobacteria were decreased, and the difference in species composition was significant. The abundance of metabolic functions related to nutrient cycling and the abundance of chemoheterotrophy ecological functions was decreased. The bacterial diversity of sugar beet rhizosphere soil was negatively correlated with the leaf disease index and positively correlated with sugar yield. The sugar beet yield was negatively correlated with the abundance of proteobacteria and actinobacteria, while positively correlated with the abundance of acidobacteria, chemoheterotrophy function, and nitrogen fixation function. This study identified the soil reasons for the decline of sugar beet yield in long-term sugar beet cultivation areas and provided a reference basis for improving soil properties and sugar beet productivity.