Format: ORAL

Eli Hartung1, Soumyadev Sarkar2, Anna Kazarina1, Kian Fogarty1, Brad Olson1, Matt Galliart3, Jack Sytsma1, Ari Jumpponen1, Sonny Lee1, Loretta Johnson1

1 Division of Biology, Kansas State University, 2 University of Arizona, 3 Fort Hays State University

Andropogon gerardii (big bluestem) is a dominant grass of the US Great Plains and its broad distribution across a steep rainfall gradient has given rise to locally adapted wet and dry ecotypes. While abiotic factors that drive local adaptation have been well-studied, little is known about the role of soil microbiomes in local adaptation. We used reciprocal inoculation to investigate how home and away microbiomes affect local adaptation. We collected seed and A. gerardii rhizosphere soils from prairies in Kansas (dry ecotype, 580 mm rainfall year-1) and Illinois (wet ecotype, 1167 mm rainfall year-1). We cultured microbes from roots and native soils, and reciprocally inoculated wet and dry microbes weekly into wet and dry ecotypes growing in common garden soil for 12 weeks in greenhouse. We measured plant form and function weekly for a variety of ecological responses. We extracted mRNA from leaves to analyze transcriptome responses. Genetic background between ecotypes determined most of our results. In addition to ecotype, inoculation increased biomass, especially that of the dry ecotype by ~30%. Furthermore, ecotypes had higher chlorophyll absorbance when grown with local soil microbiomes suggesting biotic local adaptation. Gene expression differed between ecotypes with ~7000 genes differentially expressed between ecotypes. However, when ecotypes were inoculated with their local soil microbes, with whom they share evolutionary history, inoculum strongly affected diverse aspects of plant growth and development. We conclude that plant microbial interactions for ecological and genetic responses strongly depend on ecotype context.