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Dissertation/Thesis Abstract

On Germs and Germination: Uncovering the Hidden Ecology of Seedborne Bacteria and Fungi in Open-Pollinated Maize
by Nebert, Lucas Daniel, Ph.D., University of Oregon, 2018, 143; 10746309
Abstract (Summary)

Plants are inhabited by diverse species of bacteria and fungi, which affect plant health and fitness. Endophytes are bacteria or fungi that live within plant host tissues without causing symptoms of disease, and mediate important plant traits in agriculture, such as nutrient acquisition, disease resistance, and abiotic stress tolerance. However, we know little about the general ecology of endophytes, including which factors determine their compositions within plants. Seedborne transmission may represent an important source of bacterial and fungal endophytes, which can significantly impact the plant microbiome and plant traits. However, seeds are also a vehicle for transmission of plant pathogens. Seeds are commonly treated to control against seedborne pathogens, and increasingly bacteria and fungi are inoculated onto seeds to serve as biological control against pathogens. My dissertation explores the theoretical and applied ecology of seedborne endophytes of maize, including their interactions with pathogenic Fusarium fungi, and with seed treatments designed to control Fusarium.

In Chapter II, I examine factors that affect the transmission of seedborne fungal endophytes and Fusarium into maize seedlings, including the influence of soil microbiota, and the impact of disinfection and biological control seed treatments. In Chapter III, I determine the long-term effects of seed disinfection and biological control inoculants on maize bacterial and fungal endophytes and Fusarium pathogenicity across three different farms. In Chapter IV, I recruit maize seed growers across the Pacific Northwest and U.S. to participate in a broadscale study of seedborne endophytes. Across submitted seed samples, I find commonly occurring seedborne endophyte taxa, and delineate how maize varieties interact with environmental factors to affect the composition and diversity of seed-associated endophytes in seeds. Throughout these chapters, I explore the potential applications of seedborne endophytes in agriculture, particularly as a source for biological control against Fusarium in maize, and speculate how seed treatments can have significant, lasting impacts on the plant microbiome.

Indexing (document details)
Advisor: Bohannan, Brendan, Bridgham, Scott
Commitee: Light, Ryan, Ocamb, Cynthia, Roy, Bitty
School: University of Oregon
Department: Environmental Studies Program
School Location: United States -- Oregon
Source: DAI-B 79/09(E), Dissertation Abstracts International
Subjects: Ecology, Microbiology, Agriculture
Keywords: Corn, Endophyte, Fusarium, Maize, Microbiome, Seeds
Publication Number: 10746309
ISBN: 978-0-355-85891-4
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