Plants harbor diverse microbial communities that play a vital role in health and growth. Interactions between host plant and its microbial communities are pivotal to grassland function and ecosystem sustainability. Our focal plant, Andropogon gerardii (big bluestem), is a foundation perennial grass which comprises up to 80% of biomass in prairie and makes up the main forage for cattle. Widely planted in conservation grasslands, the species’ range spans a sharp precipitation gradient giving rise to wet and dry ecotypes in the Great Plains. Given the agricultural and conservation significance, we must understand how host-microbiome interactions affect functioning of ecotypes of this dominant grass across the precipitation gradient. We utilize a ten-year-long reciprocal garden experiment spanning western Kansas to Illinois where wet, mesic and dry ecotypes of A. gerardii have been reciprocally planted and phenotypically characterized. We aim to gain insights into the microbiome diversity of wet and dry ecotypes of A. gerardii and determine the extent to which host ecotypes interact with the microbiome and test for presence of core microbiome in these ecotypes. Here, we examine microbiomes of dry and wet ecotypes grown reciprocally in Hays Kansas (rainfall 580 mm) and Carbondale Illinois (rainfall 1200 mm) respectively.
Results/Conclusions
We used Illumina sequencing of 16S rRNA V4 amplicon from the rhizosphere of dry and wet ecotypes of A. gerardii in both Hays Kansas and Carbondale Illinois to characterize the bacterial assemblage within the rhizosphere. The evenness, represented by the Shannon index and the phylogenetic diversity, was in general similar between rhizosphere samples in both ecotypes. Regarding the beta diversity, Principle Coordinate Analysis (PCoA) with Bray-Curtis dissimilarity revealed that rhizosphere samples cluster separately based on ecotypes as well as locations, suggesting that the microbial community of the dry and wet ecotype is relatively unique from one another within these locations. This aligns with experimentally observed phenotypic variations between wet and dry ecotypes. For instance, the dry ecotype showed drought adaptation with reduced blade area, thicker leaves, and greater root:shoot ratio compared to the wet ecotype. The results from this study lay a foundation to establish the relationship between ecotypic impacts on the rhizobiome composition and function, microbially mediated processes and plant host interactions in A. gerardii. Understanding the microbiome of A. gerardii and its ability to confer drought tolerance are vital to predicting and developing tools for drought resistance and conservation