Abstract: The North American tallgrass prairie is a relatively understudied ecosystem that is increasingly threatened as global climate change increases average temperatures and drought frequency. Fire suppression, plowing under of native grasses, and the replacement of native plants with monoculture has altered the native soil and plant microbial communities. Associated microbial communities assist in the ability to adapt to extreme environmental conditions for many grasses. Tripsacum dactyloides (Eastern gamagrass) is a perennial grass native to the tallgrass prairie. It has a large range across central North America and has shown both drought tolerance properties and the ability to withstand periodic flooding.
Specimens of T. dactyloides were collected from native populations, across an east-west precipitation gradient, particularly present in Kansas, Oklahoma, and Texas. We chose 24 genotypes whose origins spanned this precipitation gradient and were then grown in a common garden for several years. We then established a field experiment in which we took 10 replicates of each genotype and subjected 5 to a drought treatment under rainout shelters, and the other 5 replicates to the ambient environment precipitation. We hypothesized that genotypes from western more regions would fare better under drought conditions, compared to genotypes from eastern more regions. We also hypothesized that the composition of the microbiomes would shift over the course of the drought treatment, to favor microbes that help the host plants tolerate drought. Our preliminary results indicate that the structure of the microbial communities in T. dactyloides is influenced by both the plant's genotype and the environmental at its location of origin, with microbes associated with plants from drought-prone locations showing greater drought resistance and an increased ability to confer drought tolerance to their host plants (p=0.02) Furthermore, our findings suggest that drought-adapted microbial communities confer significant growth benefits to T. dactyloides, with plants hosting these microbes exhibiting both increased total biomass (p=0.05) and larger root systems (p=0.01), relative to plants with non-drought-adapted microbiomes.
A greater understand of drought adaptation in plants and their microbial communities can help ensure healthy tall grass prairie function and findings from this research can be applied to conservation work in this fragile ecosystem. A greater understanding of the symbiosis between plants and their microbial communities is essential for developing more tolerant crops as agricultural systems are impacted by global shifts in climate patterns.
