Rhizosphere community recruitment dynamics of the common dandelion (Taraxacum officinale)

Background/Question/Methods

Microbial communities within the rhizosphere are essential to plant growth and health. Relationships between plants and their microbes are specialized such that plant species-specific rhizosphere communities tend to be different from even the bulk soils immediately surrounding the plant. Despite the important role of microorganisms in plant rhizospheres, there is a paucity of knowledge regarding recruitment of these communities by the host plant. Understanding the establishment of species-specific microorganisms can provide unique insights into a plant’s range limits, tolerances, and even historical biogeography. In order to investigate the dynamics of the plant-microbe relationship across a wide range of ecosystems, the ubiquitous invasive weed, the common dandelion (Taraxacum officinale), is the focus of the current study. The objective of the study was to determine the ability of the dandelions, following sterilization, to recruit their associated rhizosphere community out of different soils. After collection from a central location, dandelion roots were surface sterilized and transplanted in 30 different soils. Rhizosphere communities were assessed after 1 and 4 weeks of growth and compared to bulk soil and unmanipulated dandelions. Bacterial and fungal assemblages were determined by amplicon sequencing on the Illumina platform amplifying portions of the 16S and 18S rRNA genes, respectively. 

Results/Conclusions

One week after sterilization and transplantation, microbial communities in the rhizosphere were not distinct from those in source soil. Principle coordinate analysis revealed tight clustering of communities from transplanted replicates with those from bulk soil from the same source location, while unmanipulated rhizospheres were tightly clustered. Four weeks after manipulation, however, preliminary results show that the relationship between rhizospheres and bulk soil were no longer strongly associated, and microbial communities of transplanted dandelions began to more closely resemble those of unmanipulated dandelions. Analysis of the core community of the 4 week samples showed 12 OTUs present in at least 90% of the recruited rhizosphere samples. Of these, 11 OTUs were also core in the unmanipulated rhizospheres while only 3 were shared with the bulk soils. Two OTUs were common across all sample types. These results suggest dandelions are capable of recruiting a core microbiome out of any soil type. This core microbiome may not only be an important contributor to the invasive success of this ubiquitous weed, but may also have potential applications for expanding range limits and tolerances of other plant species.