Microecological mechanisms of mountainous forest cultivated ginseng growth vigor and saponin accumulation, and the characterization of bionic microbial fertilizer

Abstract

Introduction: A study on the soil microecological mechanisms influencing the growth vigor and saponin accumulation of mountainous forest cultivated ginseng (MFCG) under various forest types.

Methods: Using MFCG from different forest types as experimental material, the correlation and functional analysis of MFCG growth vigor, ginseng saponin content, and soil nutrient elements in their rhizosphere were conducted to clarify the soil microecological mechanisms by which different forest types affect the growth vigor and saponin accumulation of understory ginseng. Based on these microecological mechanisms, a bionic microbial fertilizer was developed and characterized.

Results: The agronomic traits and saponin content (Re, Rc, Rb2, and Rb3) of MFCG in the Pinus sylvestris var. mongholica Litv. (PSV) group were significantly higher than those in the Quercus mongolica Fisch. ex Ledeb. (QMF) and Larix gmelinii (Rupr.) Kuzen (LGK) groups (p < 0.05). The total content of these four monomeric saponins in the PSV group was 35.1 and 45.56% higher than that in the QMF and LGK groups, respectively. Significant differences (p < 0.05) were observed between the PSV group and the QMF and LGK groups in terms of the rhizosphere soil microbial diversity and physicochemical indicators such as nutrient elements. The agronomic traits and saponin content of MFCG were positively correlated with chemical indicators in the rhizosphere soil, including Cu, Ca, Mg, Zn, B, Fe, Mo, Mn, Organic matter (OM), Available phosphorus (AP), Available nitrogen (AN), and Available potassium (AK). Based on the microbial diversity and nutrient elements positively correlated with MFCG in the rhizosphere soil, a bionic microbial fertilizer formula was optimized.

Discussion: The microecological mechanism behind the growth vigor and saponin accumulation of understory ginseng involves an increase in beneficial microorganisms and nutrient elements, along with a reduction in harmful microorganisms and detrimental elements. The bionic microbial fertilizer promoted MFCG growth and saponin accumulation while improving soil nutrient levels, bulk density, and water-holding capacity.

Keywords: bionic microbial fertilizer; ginseng; growth vigor; microecological mechanisms; saponin accumulation.

Figure 1

(A–G) Agronomic traits of MFCG. Different letters above the plots indicate significant differences between treatments (n = 20).

Figure 2

The concentrations of nine major ginsenosides in MFCG. (A–D) High-performance liquid chromatogram of ginsenosides detected from MFCG. S, Standard curves of nine ginsenosides; 1–9: Rg1, Re, Rf, Rb1, Rg2, Rc, Rb2, Rb3, Rd. detected from ginseng. (E–N) Ginsenoside content of MFCG. Different letters above the plots indicate significant differences between treatments (n = 4).

Figure 3

Effects of different forest types on the diversity of rhizosphere microbial communities in MFCG. (A1,A2) Venn diagrams of OTUs for soil fungi and bacteria, respectively. (B1–B4) ACE index, Chao 1 index, Shannon index, Simpson index for fungi. (B5–B8) ACE index, Chao 1 index, Shannon index, Simpson index for bacterias (*p < 0.05, **p < 0.01, n = 4). (C1,C2) PCoA results of fungal and bacterial communities, respectively (p < 0.05, n = 4).

Figure 4

Analysis of soil microbial community composition and dominant communities among different forest types MFCG rhizosphere soil under different. (Α1,A2) Cumulative histograms of fungi and bacterial community composition (relative abundance (%) of ASVs at the phylum level). (B1,B2) Intergroup ANOVA of the top ten fungi and top ten bacteria with highest relative abundance at the genus level, respectively. Different letters above the plots indicate significant differences between treatments (p < 0.05, n = 4).

Figure 5

Functional predictions of fungi and bacteria in the rhizosphere soil of ginseng under different forest types. (A1–A3) Functions of fungal communities predicted by FUNGuild. (B1) Level 1 Functional prediction of bacterial communities. (B2) Level 2 Functional prediction of bacterial communities. (B3) Level 3 Functional prediction of bacterial communities (n = 4).

Figure 6

Correlation between Ginsenoside content, agronomic traits and rhizosphere microbial community based on Spearman’s correlation coefficient. (A1,A2) Analysis of the relationship between the top 10 fungi and bacteria and ginsenosides. (B1,B2) Analysis of the relationship between the top 10 fungi and bacteria and ginseng agronomic traits. RFW, Root fresh weight; RT, Root thickness; ST, Stem thickness; LW, Leaf width; PH, Plant height; LL, Leaf length; MRL, Main root length. (C1,C2) Correlation analysis of the chemical properties of MFCG rhizosphere soil with ginsenoside content and agronomic traits, respectively. OM, organic matter; AN, available nitrogen; AP, available phosphorus; AK, available potassium; Asterisks denote significant differences (*p < 0.05, **p < 0.01, ***p < 0.001, n = 4).