Structural and Functional Analysis of the Bacterial Community in the Soil of Continuously Cultivated Lonicera japonica Thunb. and Screening Antagonistic Bacteria for Plant Pathogens

Continuous cropping is the main form of cultivation in Chinese agriculture. The bacterial community plays an important role in maintaining the healthy growth of plants. However, there are few reports on the composition and dynamics of the bacterial community structure under continuous cropping of Lonicera japonica Thunb. High-throughput sequencing was used to monitor the variation in the soil bacterial community structure of different monocropping years of Lonicera japonica Thunb., as well as the correlation between soil characteristics and bacterial community. Meanwhile, antagonistic bacteria for Fusarium oxysporum pathogens were isolated and functionally verified by culture-dependent techniques and pot experiments. Bacterial community diversity and structure changed significantly with the increase in the years of Lonicera japonica Thunb. succession. However, some beneficial bacteria, such as Bacillus and Nitrosospira, were gradually depleted. The complexity of the bacteria co-occurrence networks decreased with increasing years of cropping. FAPROTAX-based functional prediction showed that the abundance of genes related to carbon, nitrogen, sulfur metabolism and chitinlysis were reduced with the extended crop succession. Furthermore, the three Bacillus strains that were strongly antagonistic toward Fusarium oxysporum and the pot experiment demonstrated they significantly promoted Lonicera japonica Thunb. growth. Our research provides theoretical support for the development of microbial fertilizers that are beneficial to plants.