Date of Completion

2020

Document Type

Honors College Thesis

Department

Biological Sciences Program, CALS

Thesis Type

Honors College

First Advisor

Deborah A. Neher

Keywords

anaerobic soil disinfestation, vermicompost, soilborne disease suppression, organic amendments, Bray-Curtis similarity, soil microbiome

Abstract

Composts are not only beneficial to plants as available nutrients but for their suppression against pathogens such as the global fungal plant pathogen, Rhizoctonia solani. First, a plate competition assay and a suppressive colony assay were used to investigate the role of the soil microbiota in the suppression of R. solani by two different management techniques, anaerobic soil disinfestation (ASD) and vermicompost. R. solani grew more on agar plates with sterile soil than on plates with non-sterile soil, indicating the importance of the ASD and vermicompost microbiomes in R. solani suppression. R. solani was suppressed—indicated by zones of inhibition around colony forming units—by more bacteria than fungi. ASD soil contained more suppressive bacteria than vermicompost or untreated soil. Suppressive colonies of Actinobacteria from ASD and untreated soil were phenotyped for carbon utilization using Biolog EcoPlates™ and showed greater phenotypic diversity in ASD soils. Secondly, I characterize how incorporation of vermicompost and R. solani infestation of soil affects composition of soil and rhizosphere microbiomes and health status of radish (Raphanus sativus) plants. The composition of microbial communities in vermicompost and untreated bulk soil and rhizospheres were sequenced using 16S amplicons. Microbial community composition was influenced by sampling location (root vs. soil), amendment, presence of R. solani, and plant health status.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

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