Date of Award

Fall 2025

Project Type

Thesis

Program or Major

Biological Sciences

Degree Name

Master of Science

First Advisor

Anna O'Brien

Second Advisor

Victoria Jeffers

Third Advisor

Matthew MacManes

Abstract

Microbial inoculants present a potential alternative to artificial fertilizers and other chemical products in agriculture, yet microbial products derived from non-native microbes may pose ecological risks or fail to thrive. On the other hand, creating microbial inoculants from local microbes via “microbiome breeding” can be unpredictable. Here, the aquatic plant Lemna minor (duckweed), microbes isolated from duckweed, and microbes isolated from other, co-occurring aquatic plants was used to evaluate if the evolutionary distance between hosts from which microbes are sourced is a predictor of the success in “breeding” locally derived microbiomes to promote duckweed growth. “Microbiome breeding” was performed on communities built from 25%, 50%, or 100% duckweed-associated microbes, paired with 75%, 50%, or 0% microbes from another, locally co-occurring host, where the phylogenetic distance of this other host to duckweed varied across 6 levels.

While the derived communities did not have on average significantly different effects on growth from the ancestral communities, high variation between treatments and replicates demonstrated the unpredictability of microbiome breeding. However, a non-linear relationship between host phylogeny and the relative growth rate of the derived communities was observed, such that starting communities including microbes from very close or very distantly related hosts improved breeding effectiveness. 16s rRNA sequencing on the initial and end communities shows a loss of diversity and convergence of microbiomes that initially differed over the course of the experiment.

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