Establishment to senescence: plant-microbe and microbe-microbe interactions mediate switchgrass sustainability

Mary K. Firestone, University of California, Berkeley (Principal Investigator)

Kelly Craven, Michael Udvardi, Wolf Scheible, Malay Saha, Samuel Roberts Noble Foundation

(Co-Investigators)

Jizhong Zhou, Liyou Wu, University of Oklahoma (Co-Investigators)

Jennifer Pett-Ridge, Lawrence Livermore National Laboratory (Co-Investigator)

Eoin Brodie, Trent Northen, Peter Nico, Lawrence Berkeley National Laboratory (Co-Investigators)

Plants and microorganisms have coevolved for millions of years. Understanding the biochemical and genetic basis of beneficial plant-microbial interactions is a major challenge for agriculture, forestry, and invasive species management. Better knowledge of the molecular interactions between plants and microbes will benefit sustainable crop management generally. This is particularly relevant to plants such as switchgrass, a native perennial grass, which has been identified as one of the most promising bioenergy crops in the U.S. Switchgrass has the potential to provide high-yielding biomass even on marginal soils that are unsuitable for traditional agricultural crops. A persistent concern for bioenergy cultivation of switchgrass, with low-input management, is improving seedling establishment and resistance to abiotic and biotic stresses. We hypothesize that successful establishment and sustainable cultivation of switchgrass in marginal soils is in part enabled by beneficial plant-microbial interactions, and that key ecosystem services ranging from carbon sequestration and increased soil fertility to promotion of diverse soil microbial and mesofaunal communities result from a complex network of plant–microbial interactions.

To understand the bases of switchgrass productivity and potential environmental effects in marginal soils, we propose to dissect the key molecular mechanisms that differentiate plant–microbial interactions within superior genotypes adapted to a range of resource limitations. Analyses will target plant-microbe interactions during establishment, to gain insight into how symbiotic and associative microbes improve plant performance and biomass production under nutrient- and water-limited conditions. Our experiments will incorporate multiple levels of experimental complexity. We will identify core mechanisms using simplified systems and validate hypothesized mechanisms using field experiments.

Our work has four primary objectives: (1) Identify high- and low-performing switchgrass genotypes in marginal soils; determine the functional succession of plant-associated microbial communities during successful switchgrass establishment. (2) Characterize plant–microbe and microbe–microbe interactions in switchgrass and its associated microbial community, particularly when challenged by water or nutrient stress. (3) Determine how low-input switchgrass production in marginal soils may enhance ecosystem sustainability metrics such as: carbon storage, nutrient availability, and soil food webs. (4) Integrate and synthesize experimental data to identify plant-microbes interactions and the underlying mechanisms critical to switchgrass effects on ecosystem sustainability.