Date of Award

5-2026

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Biology

Thesis Sponsor/Dissertation Chair/Project Chair

Jennifer Adams Krumins

Committee Member

Matthew Schuler

Committee Member

Dirk Vanderklein

Abstract

Plants recruit soil microorganisms to help mediate biotic stressors such as herbivory, forming dynamic communities in the rhizosphere known as the root microbiome. This study investigated whether artificial herbivory could induce shifts in the root microbiome of tomato (Solanum lycopersicum) and cucumber (Cucumis sativus) and whether those shifts could be transferred to subsequent plants as a soil legacy effect. Plants were grown in sterilized or non-sterilized soil with or without simulated herbivory across two experimental phases, with Phase 2 plants receiving inoculum conditioned by Phase 1 plants. Bacterial community composition was assessed via 16S rRNA amplicon sequencing and analyzed using alpha diversity (Shannon index) and beta diversity (Bray-Curtis/PCoA) metrics. Soil sterilization history and the continuity of microbial inoculum across experimental phases were the dominant determinants of both diversity and composition, with the effects of herbivory being contingent upon these soil legacy factors. In non-sterilized soils, herbivory led to increases in Shannon diversity of subsequent plants, whereas in sterilized soils the same disturbance triggered a decrease, suggesting that an intact and diverse microbial community is a prerequisite for adaptive recruitment responses to herbivore stress. Community composition converged within treatment groups between experimental phases, with non-sterilized samples showing greater compositional continuity across phases than their sterilized counterparts. These findings highlight the foundational role that soil legacy and legacy continuity play in structuring belowground bacterial communities and have important implications for integrating microbial ecology into sustainable agricultural practices.

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