No Accession-Specific Effect of Rhizosphere Soil Communities on the Growth and Competition of Arabidopsis thaliana Accessions

Soil communities associated with specific plant species affect individual plants' growth and competitive ability. Limited evidence suggests that unique soil communities can also differentially influence growth and competition at the ecotype level. Previous work with Arabidopsis thaliana has shown that accessions produce distinct and reproducible rhizosphere bacterial communities, with significant differences in both species composition and relative abundance. We tested the hypothesis that soil communities uniquely affect the growth and reproduction of the plant accessions with which they are associated. Specifically, we examined the growth of four accessions when exposed to their own soil communities and the communities generated by each of the other three accessions. To do this we planted focal accessions inside a ring of six plants that created a “background” soil community. We grew focal plants in this design in three separate soil treatments: non-sterile soil, sterilized soil, and “preconditioned” soil. We preconditioned soil by growing accessions in non-sterile soil for six weeks before the start of the experiment. The main experiment was harvested after seven weeks of growth and we recorded height, silique number, and dry weight of each focal plant. Plants grown in the preconditioned soil treatment showed less growth relative to the non-sterile and sterile soil treatments. In addition, plants in the sterile soil grew larger than those in non-sterile soil. However, we saw no interaction between soil treatment and background accession. We conclude that the soil communities have a negative net impact on Arabidopsis thaliana growth, and that the unique soil communities associated with each accession do not differentially affect growth and competition of study species

Multi-Generation Ecosystem Selection of Rhizosphere Microbial Communities Associated with Plant Genotype and Biomass in Arabidopsis thaliana

The role of the microbiome in shaping the host’s phenotype has emerged as a critical area of investigation, with implications in ecology, evolution, and host health. The complex and dynamic interactions involving plants and their diverse rhizospheres’ microbial communities are influenced by a multitude of factors, including but not limited to soil type, environment, and plant genotype. Understanding the impact of these factors on microbial community assembly is key to yielding host-specific and robust benefits for plants, yet it remains challenging. Here, we conducted an artificial ecosystem selection experiment for eight generations of Arabidopsis thaliana Ler and Cvi to select soil microbiomes associated with a higher or lower biomass of the host. This resulted in divergent microbial communities shaped by a complex interplay between random environmental variations, plant genotypes, and biomass selection pressures. In the initial phases of the experiment, the genotype and the biomass selection treatment had modest but significant impacts. Over time, the plant genotype and biomass treatments gained more influence, explaining ~40% of the variation in the microbial community’s composition. Furthermore, a genotype-specific association of plantgrowth-promoting rhizobacterial taxa, Labraceae with Ler and Rhizobiaceae with Cvi, was observed under selection for high biomass

Morphological differentiation in a common garden experiment among native and non-native specimens of the invasive weed yellow starthistle (Centaurea solstitialis)

Understanding the differences between weedy and non-weedy plant populations is important because they may provide clues to genetic factors that create invasive species, as well as important insights into local adaptation. We studied weedy, non-native (California and Argentina) and non-weedy, native populations (Republic of Georgia and Turkey) of Centaurea solstitialis in a common garden setting. Specimens grown from non-native seed stock were generally taller, had longer leaves with more surface area, and flowered earlier than plants grown from native seed stock. Plants from California tended to be much taller, on average, than plants from any other country, and plants from the Republic of Georgia tended to bolt much later than plants from other countries. When we compared neutral genetic variation at microsatellite or simple sequence repeat markers using AMOVA to quantitative morphological variation, we found that quantitative variation was much more likely to be partitioned among regions than genetic variation. We also evaluated F ST values against Q ST (F ST/Q ST analysis) and found evidence for possible selection on plant height and leaf length in the non-native regions. Our results suggest that local adaptation may play a role in the success of C. solstitialis as an invasive weed.Fil: Eriksen, Renée L.. University of Massachusetts-Boston; Estados UnidosFil: Desronvil, Theodora. University of Massachusetts-Boston; Estados UnidosFil: Hierro, Jose Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; ArgentinaFil: Kesseli, Rick. University of Massachusetts-Boston; Estados Unido

Mean mass (±SE) of focal plants Col, Cvi, <i>Ler</i>, Rld with each of the four background accessions, in all three soil types (• sterile soil, ▾ non-sterile soil, ▪ preconditioned soil).

<p>Mean mass of sterile, and non-sterile, solo plants are given by lines surrounded by dark gray and light gray regions depicting ±SE. Means and SE for solo plants are shown for reference and are the same for all background accessions because they grew without background plants (N = 15).</p

Mean leaf number, inflorescence height, and silique number (±SE) showing significant interactions between focal accession (• Col, ○ Cvi, ▾ <i>Ler</i>, Δ Rld) and background accession.

<p>Letters indicate significant differences between treatments using a Tukey-Kramer post-hoc paired comparison adjustment (N = 15).</p

Schematic diagram of the experimental design.

<p>Each circle represents an experimental treatment. Letters represent individual plants. C = Col; V = Cvi; L = <i>Ler</i>; R = Rld.</p

Mean mass (±SE) of focal plants in sterile, non-sterile, and preconditioned soil (N = 15).

<p>Mean mass (±SE) of focal plants in sterile, non-sterile, and preconditioned soil (N = 15).</p