Paenibacillus polymyxa and Bacillus cereus co-bacterial agent promotes ginseng resistance to diseases and improves yield, quality and pesticide degradation through regulating rhizosphere microbial community structure and potential function

Abstract

Background: The ginseng endophyte Paenibacillus polymyxa Pp-7250 (Pp-7250) have multifaceted roles such as preventing ginseng diseases, promoting growth, increasing ginsenoside accumulation and degrading pesticide residues, these effects still room for improvements. Composite fungicide is an effective means to improve the biocontrol effect of fungicide, but the effect of Pp-7250 in combination with its symbiotic bacteria on ginseng needs to be further researched, and its mechanism of action still remains to be elucidated. In order to elucidate the effect of Paenibacillus polymyxa and Bacillus cereus co-bacterial agent on the yield and quality of understory ginseng, as well as to investigate its mechanism of action. Firstly, the effects of Bacillus cereus (BS), Paenibacillus polymyxa Pp-7250(PS) and Paenibacillus polymyxa and Bacillus cereus co-bacterial agent (PB) treatments on ginseng yield, ginsenoside content, disease prevention and pesticide degradation rate were evaluated by field experiments. Secondly, differences in microbial communities in ginseng rhizosphere soils with different treatments were analyzed using high‐throughput amplicon sequencing. Finally, correlation analysis was performed to elucidate the mechanism of action of PB co-bacterial agent in improving the yield and quality of ginseng. Results: The results indicate that PB treatment improved ginseng yield, ginsenoside accumulation, disease prevention and pesticide degradation. The mechanism is that PB treatment increased the abundance of beneficial microorganisms Rhodanobacter, Pseudolabrys, Gemmatimonas, Bacillus, Paenibacillus, Cortinarius, Russula, Paecilomyces, Trechisporaincreased and decreased the abundance of pathogenic microorganisms Ellin6067, Acidibacter, Fusarium, Tetracladium, Alternaria, and Ilyonectria in ginseng rhizosphere soil. PB co-bacterial agent enhanced the function of microbial metabolic pathways, biosynthesis of secondary metabolites, biosynthesis of antibiotics, biosynthesis of amino acids, carbon fixation pathways in prokaryotes, DNA replication, terpenoid backbone biosynthesis, and decreased the function of microbial plant pathogen and animal pathogen. This study provided a theoretical reference for indepth research on improving the yield and quality of ginseng. Conclusion: The combined agent of Paenibacillus polymyxa and Bacillus cereus may be a potential biocontrol agent to promote the resistance of ginseng to disease, improve the yield, quality and pesticide degradation.