Examining the root microbiome in wild populations of Solanum dulcamara across extremely contrasting habitats

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Kristin A. E. Aleklett and Åsa Lankinen, Department of Plant Protection, Swedish University of Agricultural Sciences, Alnarp, Sweden

Background/Question/Methods
While we have learnt a lot about the plant microbiome over the past decade, research has mainly been focused on model species or crops in agricultural systems. These studies provide useful information, but may miss out on the larger picture of how plant microbiomes are shaped and operate in the wild. In this study, we examined whether the root microbiome in wild populations of Solanum dulcamara L. (Bittersweet nightshade) varied across different types of environments (beach, forest, rural, urban), based on abiotic factors of the environment (eg. humidity, soil nutrient content) or if it hosted a similar root microbiome independently of which environment the species was growing in.
Solanum dulcamara is a perennial woody vine native to Eurasia, and a wild relative to commercially important crops such as potato and tomato. In North America, S. dulcamara is classified as invasive by the USDA as it spreads rapidly, propagating both vegetatively – growing large amounts of runners and shoots, and sexually – producing tomato-like seed-filled berries that are readily eaten and spread by birds. An interesting feature of S. dulcamara is that it is known to grow and thrive in extremely variable environments – from beaches to roadside ditches and swampy understories in the forest. It has even been suggested that there are different sun and shade ecotypes within the species, with different abilities to use light efficiently for photosynthesis. However, researchers have failed to fully link this ability to occupy contrasting habitats to local adaptation, and instead suggest that that the species manages to thrive in both flood and drought environments by having high levels of phenotypic plasticity.
Results/Conclusions
In this study, we surveyed eight wild populations of Solanum dulacamara, documenting population characteristics, surrounding plant and insect diversity, and individual plant traits. We then compared the microbial root communities between populations, four different habitat types (forest, beach, urban, rural) and to root microbiomes of a neighbouring plant species growing in the same environment. Our results show that sand-dune populations produced significantly more seeds than populations in wetter environments, potentially demonstrating a trade-off between sexual and vegetative reproduction based on moisture, and link these phenotypic differences to the bacterial and fungal microbiome of the root systems.