Root exudation and rhizosphere microbial recruitment are influenced by novel plant trait diversity in carrot genotypes

Authors: ANDERSON, HANNAH - University Of Wisconsin; CAGLE, GRACE - University Of Wisconsin; MAJUMDER, ERICA - University Of Wisconsin; SILVA, ERIN - University Of Wisconsin; DAWSON, JUILE - University Of Wisconsin; Simon, Philipp; FREEDMAN, ZAC - University Of Wisconsin

Submitted to: Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2024
Publication Date: 7/11/2024
Citation: Anderson, H., Cagle, G., Majumder, E., Silva, E., Dawson, J., Simon, P.W., Freedman, Z. 2024. Root exudation and rhizosphere microbial recruitment are influenced by novel plant trait diversity in carrot genotypes. Soil Biology and Biochemistry. 197. https://doi.org/10.1016/j.soilbio.2024.109516.
DOI: https://doi.org/10.1016/j.soilbio.2024.109516

Interpretive Summary: Terrestrial plants evolved in close association with soil microorganisms, mediating both positive and negative plant-microbe interactions through root growth and the rhizosphere. The rhizosphere, defined as the narrow zone of soil in direct contact with an actively growing plant root, is a hotspot for plant-soil substrate flow and microbial activity. It is well documented that rhizosphere microbial community composition and functions differ from that of the bulk soil in a given field, and these differences could ultimately shape plant and soil functional outcomes as a result of shifts in microbial metabolism, for example, by increasing soil nutrient availability. Given these plant-microbe interactions, the aim of this study was was to advance understanding of the mechanisms that shape rhizosphere microbial communities across a spectrum of plant trait diversity by co-investigating the diversity of root exudate (which refers to the chemicals excreted by the carrot on the root surface), soil composition and rhizosphere microbial community in a field setting. We found that both the composition of carrot root exudates and the variation in microbial communities were strongly and significantly associated with carrot genotype. This variation likely has an effect on carrot growth and on the nutrient composition of the carrot crop. These results are of interest to carrot growers, vegetable breeders, soil scientists, microbiologists, and consumers.

Technical Abstract: Root exudate composition can influence of rhizosphere microbial recruitment and is tightly controlled by plant genetics, however, little research has profiled root exudate in vegetable crops or determined their role in rhizosphere microbial community and metabolite composition. It is also not well understood how root exudates and resulting rhizosphere dynamics shift across plant trait diversity and with the development of novel crop genotypes. To address these knowledge gaps, this study paired metabolomics and microbiome analyses to evaluate potential associations between the composition of exudates, soil bacterial and fungal communities and soil metabolites across four genotypes of organically produced carrot of differential breeding histories, including two experimental genotypes and two cultivars. An heirloom genotype and a novel nematode resistant genotype had a significantly different root exudate profile compared to other genotypes tested. The composition of root exudates was strongly and significantly associated with bacterial, but not fungal communities across all genotypes. Moreover, plant genotypes differentially modified soil microbial diversity and composition. Several of the taxa responsive to genotype were previously demonstrated to carry out plant-growth related functions including ammonia oxidation, nitrogen fixation, and phytohormone production. Taken together, the results of this study suggest that novel crop trait diversity and breeding.