Abstract:

Objective: This study aims to explore the structure, diversity and functional characteristics of bacterial communities in the soil, bark and leaves of healthy and diseased Idesia polycarpa plants, so as to lay a foundation for pathogenic bacteria verification and biological prevention and control of I. polycarpa diseases. Method: Based on high-throughput sequencing technology, the differences of bacterial composition, diversity and function in different organs and rhizosphere soil of healthy and diseased I. polycarpa were analyzed by OTU number, identification group, diversity index and functional prediction. Result: The sequencing results showed that different organs and areas of I. polycarpa had their own unique bacterial groups. Proteobacteria, Actinobacteria and Acidobacteria were the main bacterial groups in the soil, and Cyanobacteria and Proteobacteria were the main bacterial groups in bark and leaves. The relative abundance of Brenneria and Hafnia-Obesumbacterium of Enterobacteriaceae in the bark of diseased I. polycarpa was significantly higher than that of healthy I. polycarpa. The results of diversity analysis showed that the diversity and richness of bacterial communities in all organs and areas of I. polycarpa were soil > bark > leaf from high to low. There was no significant difference in Chao1 index, Shannon index and Simpson index between healthy and diseased plants, and the Simpson index of bacteria in diseased tree bark was significantly higher than that of healthy bark. The PICRUSt function prediction showed that the genes related to biosynthesis in rhizosphere soil of diseased I. polycarpa were enriched, and the genes related to Staphylococcus aureus infection and amino acid metabolism in bark of diseased I. polycarpa were enriched. Conclusion: The bacterial community structure and diversity in different organs and areas of I. polycarpa are affected after the plants are infected. The bacterial community structure in the leaf area is less affected. There are significantly differences in the community structure and function of bacteria betwenn the rhizosphere soil and bark. The bacterial diversity in the bark area of infected plants increases significantly, and the forest pathogenic bacteria in the infected bark have high abundance, indicating that the main disease area of I. polycarpa is the plant bark area. This study provides a theoretical basis for studying the pathogenic mechanism and disease control of I. polycarpa.

Key words: Idesia polycarpa, high-throughput sequencing, bacterial community structure, diversity, PICRUSt functional prediction