Identification of Autotoxic Compounds in Fibrous Roots of Rehmannia (Rehmannia glutinosa Libosch.)

Abstract

Rehmannia is a medicinal plant in China. Autotoxicity has been reported to be one of the major problems hindering the consecutive monoculture of Rehmannia. However, potential autotoxins produced by the fibrous roots are less known. In this study, the autotoxicity of these fibrous roots was investigated. Four groups of autotoxic compounds from the aqueous extracts of the fibrous roots were isolated and characterized. The ethyl acetate extracts of these water-soluble compounds were further analyzed and separated into five fractions. Among them, the most autotoxic fraction (Fr 3) was subjected to GC/MS analysis, resulting in 32 identified compounds. Based on literature, nine compounds were selected for testing their autotoxic effects on radicle growth. Seven out of the nine compounds were phenolic, which significantly reduced radicle growth in a concentration-dependent manner. The other two were aliphatic compounds that showed a moderate inhibition effect at three concentrations. Concentration of these compounds in soil samples was determined by HPLC. Furthermore, the autotoxic compounds were also found in the top soil of the commercially cultivated Rehmannia fields. It appears that a close link exists between the autotoxic effects on the seedlings and the compounds extracted from fibrous roots of Rehmannia.

In vitro antioxidant and antidiabetic activities of Rehmannia glutinosa tuberous root extracts

“…Its fresh and dried tuberous roots are used as a traditional Chinese medicinal ingredient for sedation, diabetes, haematological conditions, and insomnia [4][5][6] . The extract of its tuberous roots contains iridoids, monoterpenes, glycosides, fatty acids, amino acids, and microelements that have been reported to have various medical effects concerning reduction of blood pressure, blood circulation, immune capability, endocrine balance, and cardiovascular regulation [7][8][9] .…”

Screening and Identification of Harmful and Beneficial Microorganisms Associated with Replanting Disease in Rhizosphere Soil of Pseudostellariae heterophylla

“…Ma et al (2005) reported that phenolic acids not only affected the amount and diversity of microbial communities in soil, but also promoted growth of soil-borne pathogens such as Fusarium oxysporum and Phytophthora. It is reported that phenolic acids were isolated from fibrous roots and rhizosphere soil of R. glutinosa and might contribute to the autotoxicity of R. glutinosa (Li et al, 2012b). Qu and Wang (2008) found that phenolic acids selectively enhance specific microbial population in soil, and lead to the development of shifted communities with differing qualitative and quantitative compositions.…”

“…Previous studies showed that rhizospheric microbial dynamics largely governed proper soil ecosystem function and had close interaction with consecutive monoculture problems (Qu and Wang, 2008;Qi et al, 2009;Wu et al, 2009;Wu et al, 2011;Li et al, 2012b;Wu et al, 2013). Crop consecutive monoculture not only alters the physical and chemical properties of the soil, but also contributes to the development of diverse microbial groups in the rhizosphere (Minh, 2005;Lin et al, 2007;Yoneyama and Natsume, 2010;Berendsen et al, 2012;Ndabamenye et al, 2013).…”

“…Crop consecutive monoculture not only alters the physical and chemical properties of the soil, but also contributes to the development of diverse microbial groups in the rhizosphere (Minh, 2005;Lin et al, 2007;Yoneyama and Natsume, 2010;Berendsen et al, 2012;Ndabamenye et al, 2013). The autotoxic compounds were often isolated from consecutive monoculture soil, such as phenolic acid and aliphatic acid compounds, which could selectively enhance specific microbial populations in the soil which then leads to a shift in microbial communities (Qu and Wang, 2008;Li et al, 2012b). Wu et al (2011) analyzed the rhizospheric biological properties of consecutively monocultured R. glutinosa using soil metaproteomics and found that consecutive monoculture can induce the changes of microbes in the expression of proteins.…”

DNA Methylation in Rehmannia glutinosa Roots Suffering from Replanting Disease

“…Certain stresses which disturb plant growth and development have been shown to induce alterations in the pattern of methylation of genomic DNA (Ding et al, 2014;Zhong et al, 2015). Replanting disease in R. glutinosa is thought to be largely caused by the presence of its own root exudate in the soil (Wu et al, 2011;Li et al, 2012b;Ru et al, 2014), but it has not yet been established whether this acts as an agent of epigenetic alteration.…”