Assessment of the Diversity of spp. and spp. in Rhizosphere under Monoculture by Combining DGGE and Quantitative PCR.

is a perennial tonic medicinal plant, with high medicinal value. However, consecutive monoculture of this plant in the same field results in serious decrease in both yield and quality. In this study, a 3-year field experiment was performed to identify the inhibitory effect of growth caused by prolonged monoculture of . DGGE analysis was used to explore the shifts in the structure and diversity of soil and communities along a 3-year gradient of monoculture. The results demonstrated that extended monoculture significantly boosted the diversity of spp., but declined spp. diversity. Quantitative PCR analysis showed a significant increase in , but a decline in spp. Furthermore, abundance of antagonistic spp. possessing antagonistic ability toward significantly decreased in consecutively monocultured soils. Phenolic acid mixture at the same ratio as detected in soil could boost mycelial and sporular growth of pathogenic while inhibit the growth of antagonistic . CJ313. Moreover, plant bioassays showed that sp. CJ313 had a good performance that protected from infection by In conclusion, this study demonstrated that extended monoculture of could alter the and communities in the plant rhizosphere, leading to relatively low level of antagonistic microorganisms, but with relatively high level of pathogenic microorganisms.