Rhizosphere Microbiome Diversity in Field Pennycress (Thlaspi arvense L.) and its Implications for Plant and Soil Health in Eastern Washington

Andrew Spishakoff

doi:10.7273/000005373

Field pennycress (Thlaspi arvense) is a winter annual in the family Brassicaceae undergoing development as a cash and cover crop intended for biodiesel feedstock. Many of its characteristics make it a desirable choice for this purpose. It has a short growth period that allows it to be grown between rotations of other crops without competing, displays high cold tolerance, and has no food use that may raise the price. While currently largely grown in the Midwest United States, these traits make it a good candidate for winter oilseed farming in the inland Pacific Northwest (iPNW). However, given the different soils and much lower precipitation, the plant would be subject to different stresses and making agronomic cultivation more difficult in the iPNW. Current published literature points to the benefits of certain bacterial and fungal species in the rhizosphere of agricultural plants in terms of stress resistance. However, very little is currently known in regards to the microbial community present in the field pennycress rhizosphere. Therefore, studying the pennycress rhizosphere microbial community could give us insights into the organisms that confer abiotic stress resistance and which genetic lines might thrive in this environment. In order to improve some of the strong characteristics of the species, multiple pennycress mutant lines have been generated with a wide variety of useful traits. Nine genotypes were planted at three sites in Eastern Washington across a precipitation gradient with varying edaphic soil factors representative of the challenges facing dryland farming systems of the iPNW. At harvest, we collected whole plants, above- and below-ground biomass, with rhizosphere soil attached. The aerial parts of the plants were dried and weighed and the genomic DNA of the microbiome from the rhizosphere soil was used to generate amplicon libraries for both bacterial (16S) and fungal (ITS) communities. Analysis revealed the highest above-ground biomass from one specific mutant line (Spring32-10 Fad2) at the driest site, and several plant and soil health improving microbial taxa present in the rhizosphere of that mutant, such as Trichoderma spriale which enhances plant growth and provides drought resistance, and Planifilum spp. which are capable of diazotrophic Nitrogen (N) fixation. Future work will expand our understanding of the microbial diversity present across pennycress genotypes and heighten our ability to leverage the benefits of the microbiome for cultivation in the iPNW.

Rhizosphere Microbiome Diversity in Field Pennycress (Thlaspi arvense L.) and its Implications for Plant and Soil Health in Eastern Washington

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