Understanding the mechanisms of drought resistance in plants are critical, as the negative effects of climate change become more apparent. Since microorganisms in the rhizosphere play an important role in drought resistance, understanding the interactions between plants and its rhizobiome are vital to investigate plant host resilience under continuing threats of climate change. For this study, we focus on Andropogon gerardii – an ecologically dominant big bluestem of the Great Plains with wide distribution from western Kansas to Illinois. Bluestem grasses are a leading food source for livestock and are planted for restoration on over 5 million acres. In this study, we take advantage of a ten year long reciprocal garden experiment, where the seeds of native wet, mesic and dry ecotypes of A. gerardii have been reciprocally planted from western KS (rainfall 500 mm) to Illinois (1200 mm). Here, we examine the microbiomes of these ecotypes grown in the most extreme conditions in Colby KS, as a surrogate for the dry conditions expected in the future. Our overall goal is to gain insights into plant-host-microbiota associated with drought resiliency. This is done by analyzing the microbiome diversity of the rhizosphere ecotypes and how they differ in response to extreme drought.
Results/Conclusions
We extracted the root microbial DNA and profiled the 16S rRNA V4 amplicon to determine the bacterial rhizosphere’s compositional differences between the A. gerardii ecotypes. Our results showed that the host’s ecotype had an influence on the bacterial community composition but not necessarily on its diversity. The community composition in wet and mesic ecotypes was more similar to each other, congruent with strong plant phenotypic similarities, as compared to the dry ecotype. On the other hand, the bacterial community on the dry ecotype was not only different from the other two ecotypes, but there was also a high degree of dissimilarity within the ecotype, demonstrating the impact of the environment on the bacterial composition. Specifically, we found Streptomycetaceae and Rhodobacteraceae were of higher relative abundance in the dry ecotype alone. Streptomycetaceae (phylum Actinobacteria) is well known to be more abundant in precipitation-limited soils. This study enabled us to take the first step in identifying the core microbiome that may increase drought resistance in plant hosts. Identifying the functional role of these bacterial populations and their interaction with the plant host is crucial to enhance the growth of a dominant grass in the face of climate change.