Effects of a compound Trichoderma agent on Coptis chinensis growth, nutrients, enzyme activity, and microbial community of rhizosphere soil.

Background: Root rot diseases are prevalent in many Coptis chinensis Franch. production areas, perhaps partially due to the overuse of synthetic fertilizers. Synthetic fertilizers can also lead to soil degradation. Trichoderma is widely used in biofertilizers and biopesticides. This study applied a combination of four Trichoderma species (compound Trichoderma agent, CTA) to C. chinensis and evaluated its effects on growth, as well as rhizosphere soil nutrients, enzyme activities, and microbial community structure. The purpose of this study was to estimate the potential of using CTA as a biofertilizer for C. chinensis, and determine if it could, at least partially, replace synthetic fertilizers to control root rot disease and maintain soil fertility. Method: CTA, compound fertilizer and sterile water were applied to C. chinensis plants. After 60 days, the soluble sugar, soluble protein, chlorophyll of leaves, and individual weight of each plant were measured. The rhizosphere soil nutrient content, enzymatic activity, and the microbial community were also determined. The results were analyzed to evaluate the effect of CTA on C. chinensis growth and soil fertility. Results: CTA increased the soluble protein, chlorophyll, and individual weight of C. chinensis plants while compound fertilizer decreased chlorophyll. CTA increased the activities of urease and catalase in rhizosphere soil, whereas the compound fertilizer decreased urease, catalase, and alkaline phosphatase activities. CTA elevated soil pH, while compound fertilizer reduced it. CTA had no significant effects on soil nutrients and organic matter. CTA decreased the fungal number and alpha-diversity of fungi and bacteria, and both the fungal and bacterial communities were significantly different from the other two. CTA increased B/F value, which improved the rhizosphere microbial community. Both CTA and the compound fertilizer significantly altered the soil microbial community. The relative abundance of Ascomycota was higher and Basidiomycota was lower after CTA treatment than after the other two treatments, indicating that the soil treated with CTA was healthier than that of the other two treatments. CTA decreased harmful Ilyonectria mors-panacis and Corynebacterium sp. And increased beneficial Ralstonia picketti. Trichoderma spp. could exist in C. chinensis rhizosphere soil for a long time. The functional prediction results demonstrated that CTA reduced some rhizosphere phytopathogenic fungi. Correlation analysis showed that CTA elevated rhizosphere pH and enzyme activities. In summary, synthetic fertilizers damaged soil fertility, and the overuse of them might be responsible for root rot disease, while CTA could promote C. chinensis growth, improve soil and decrease the incidence and severity of C. chinensis root rot disease. Therefore, as a biofertilizer, CTA can, at least partially, replace synthetic fertilizers in C. chinensis production. Combining it with organic fertilizer will increase the potential of Trichoderma.

Effects of growing Coptis chinensis Franch in the natural understory vs. under a manmade scaffold on its growth, alkaloid contents, and rhizosphere soil microenvironment.

Background: The main planting modes currently used for the production of Coptis chinensis Franch are under the shade of a manmade scaffold or a natural understory. In this study, we analysed changes in the growth, development, and alkaloids of C. chinensis when grown in a natural understory compared with under a manmade scaffold. We also clarified the differences in the rhizosphere soil microenvironment, represented by soil physicochemical factors, enzyme activity, and microbial community structure of 1- to 5-year-old C. chinensis between the different planting modes. These results will provide theoretical guidance and scientific evidence for the development, application, and extension of ecological planting technologies for C. chinensis. Results: The results of this study showed that rhizome length, rhizome diameter, and rhizome weight all increased over time in both planting modes. The greatest rhizome length was reached in 4-year-old C. chinensis, while the greatest rhizome diameter and rhizome weight were obtained in 5-year-old C. chinensis. There was no significant difference in rhizome biomass between the two planting modes. The alkaloid content of the four common alkaloids in the rhizome of 5-year-old C. chinensis at the harvest stage met the standards found in the Pharmacopoeia of the People's Republic of China; the berberine content and total alkaloids in the rhizomes were significantly higher with natural understory planting compared to planting under a manmade scaffold. A redundancy analysis revealed that the physicochemical factors and enzyme activity of rhizosphere soil were significantly correlated with variation in microbial community structure. Soil pH, available potassium, bulk density, available nitrogen, catalase, and peroxidase were all significantly correlated with bacterial and fungal community structures. Among these, soil pH was the most important factor influencing the structures of the fungal and bacterial community. In the two planting modes, the differences in soil enzyme activity and microbial community structure mainly manifested in the rhizosphere soil of C. chinensis between different growth years, as there was little difference between the rhizosphere soil of C. chinensis in a given growth year under different planting modes. The levels of nitrogen, phosphorus, potassium, and organic matter in the rhizosphere soil under either planting mode were closely associated with the type and amount of fertiliser applied to C. chinensis. Investigating the influence of different fertilisation practices on nutrient cycling in farmland and the relationship between fertilisation and the soil environment will be key to improving the yield and quality of C. chinensis medicinal materials while maintaining the health of the soil microenvironment.