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

Jun Chen,Muhammad U Khan,Xianjin Qin,Hongmiao Wu,Juanying Wang,Wenxiong Lin,Xiaoya Wei,Linkun Wu,Sheng Lin,Yanhong Wu,Zhigang Xiao

doi:10.3389/fmicb.2017.01748

Jun Chen, Muhammad U Khan + Show 9 more

Open Access

https://doi.org/10.3389/fmicb.2017.01748

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Abstract

Radix pseudostellariae 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 R. pseudostellariae. DGGE analysis was used to explore the shifts in the structure and diversity of soil Fusarium and Pseudomonas communities along a 3-year gradient of monoculture. The results demonstrated that extended monoculture significantly boosted the diversity of Fusarium spp., but declined Pseudomonas spp. diversity. Quantitative PCR analysis showed a significant increase in Fusarium oxysporum, but a decline in Pseudomonas spp. Furthermore, abundance of antagonistic Pseudomonas spp. possessing antagonistic ability toward F. oxysporum 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 F. oxysporum while inhibit the growth of antagonistic Pseudomonas sp. CJ313. Moreover, plant bioassays showed that Pseudomonas sp. CJ313 had a good performance that protected R. pseudostellariae from infection by F. oxysporum. In conclusion, this study demonstrated that extended monoculture of R. pseudostellariae could alter the Fusarium and Pseudomonas communities in the plant rhizosphere, leading to relatively low level of antagonistic microorganisms, but with relatively high level of pathogenic microorganisms.

Highlights

As much as 70% of medicinal plants suffer from consecutive monoculture problem, known as replant disease or soil sickness
The principal component analysis (PCA) of the Denaturing gradient gel electrophoresis (DGGE) profile was performed to demonstrate the relative position of four soil samples
PCA showed that the Fusarium community in CK, FP and SP was separated from TP by the Pseudomonas-Specific DGGE

Summary

Introduction

As much as 70% of medicinal plants suffer from consecutive monoculture problem, known as replant disease or soil sickness These problems are commonly observed in the production of many Chinese medicinal herbs, including Radix pseudostellariae, Rehmannia glutinosa, Panax notoginseng, etc (Zhang and Lin, 2009). R. pseudostellariae, a perennial tonic medicinal plant, belongs to the family Caryophyllaceae with extremely high medicinal value (Zhao W.O. et al, 2015). Consecutive monoculture of this plant in the same field leads to a serious decrease in both quality and yield of roots along with poor plant performance, which severely limited production and utilization of its medicinal plant virtues (Lin et al, 2015). In order to develop the full potential of the disease-suppressive microbial community in the biological control, we need more information to unravel the different roles of this potentially important species

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