Root-Associated Microbiomes of Panax notoginseng under the Combined Effect of Plant Development and Alpinia officinarum Hance Essential Oil

Abstract

Essential oils (EOs) have been proposed as an alternative to conventional pesticides to inhibit fungal pathogens. However, the application of EOs is considerably limited due to their highly volatile nature and unpredictable effects on other microbes. In our study, the composition of bacterial and fungal communities from the rhizosphere soil of P. notoginseng under four treatment levels of Alpinia officinarum Hance EO was characterized over several growth stages. Leaf weight varied dramatically among the four EO treatment levels after four months of growth, and the disease index at a low concentration (0.14 mg/g) of EO addition was the lowest among the P. notoginseng growth stages. The content of monomeric saponins was elevated when EO was added. Bacterial and fungal diversity in the absence of plants showed a decreasing trend with increasing levels of EO. Bacterial diversity recovery was more correlated with plant growth than was fungal diversity recovery. Compared with the control (no EO addition), a low concentration of EO significantly accumulated Actinomycota, including Acidothermus, Blastococcus, Catenulispora, Conexibacter, Rhodococcus, and Sinomonas, after one month of plant-microbial interaction. Overall, the results showed that both the plant growth stage and EOs drive changes in the microbial community composition in the rhizosphere of P. notoginseng. Plant development status had a stronger influence on bacterial diversity than on fungal diversity. EO had a more significant effect on fungal community composition, increasing the dominance of Ascomycota when EO concentration was increased. Under the interaction of P. notoginseng growth and EO, a large number of bacterial genera that have been described as plant growth-promoting rhizobacteria (PGPR) responded positively to low concentrations of EO application, suggesting that EO may recruit beneficial microbes in the root zone to cope with pathogens and reduce root rot disease. These results offer novel insights into the relationship between EO application, altered microbial communities in the plant roots, plant growth stage, and disease occurrence.

Biocontrol Activity of Aromatic and Medicinal Plants and Their Bioactive Components against Soil-Borne Pathogens

“…In addition to the typical root exudates, such as sugars, organic acids, amino acids, and sterols, aromatic crops can release novel chemicals in the soil that may have a long-lasting effect on the processes arbitrated by the surrounding microorganisms. Although the production of plant secondary metabolites is relatively low [ 110 , 116 , 197 ], volatiles can form a stable concentration gradient in the soil due to the lack of turbulence [ 109 ], and the build-up of pathogenic microorganisms and other predators can thus be inhibited [ 191 ]. However, several rhizospheric microorganisms have the potential to adapt and conduct endophytic or epiphytic life.…”

Combined application of resistance inducer and Trichoderma control two tobacco soil‐borne diseases by regulating the field soil microbial composition

“…As plant biocontrol agents, Trichoderma isolates have been reported to regulate the rhizosphere soil microbiome to suppress the plant soil‐borne diseases (Pang et al., 2017). RIs extracted from traditional Chinese medicine (TCM) also altered the fungal communities in the control of Panax notoginseng root rot (Zhou et al., 2022). However, the roles of Trichoderma and RI extracted from TCM, when applied in combination, on the tobacco rhizosphere bacterial and fungal communities remain unclear.…”