Doctor of Philosophy, The Ohio State University, 2023, Plant Pathology

Plants exist in a constantly evolving microbial environment that significantly influences their growth, development, and overall well-being. Within this microbial milieu, certain bacteria play a pivotal role in enhancing plant health and growth. These beneficial bacteria are collectively referred to as plant growth-promoting bacteria (PGPB). They offer valuable services to plants, including improved nutrient absorption, heightened growth stimulation, and increased resilience against pathogens and the other environmental adversities. PGPB engage with plants through diverse modes of interaction, such as root colonization, endophytic association, or rhizosphere competence. An in-depth comprehension of the molecular mechanisms and ecological dynamics governing these interactions is essential for unlocking the potential of PGPB in promoting sustainable agriculture and environmental remediation. In Chapter 1, I provide an overview of current methods used to detect and diagnose Pseudomonas syringae. This encompasses traditional approaches like culture isolation and microscopy, as well as modern techniques such as PCR and ELISA. Furthermore, I explore the upcoming advancements in this domain, emphasizing the necessity for highly sensitive and specific methods to detect pathogens even at low concentrations. Additionally, I delve into approaches for diagnosing P. syringae infections when they coexist with other pathogens. Chapter 1 Figures can be found in Appendix A. In Chapter 2, I present a significant protocol for monitoring the progression of gray mold fungal infection at various developmental stages of strawberries. I detail three distinct in vivo inoculation methods for Botrytis cinerea on strawberry plants, focusing on early, middle, and late stages of strawberry growth. Chapter 2 Figures can be found in Appendix B. In Chapter 3, I introduce Bacillus proteolyticus OSUB18 as a novel inducer of ISR (Induced Systemic Resistance). This bacterium enhances plants' r (open full item for complete abstract)

Committee: Ye Xia (Advisor); Christopher Taylor (Committee Member); Yu (Gary) Gao (Committee Member); Lisa (Beck) Burris (Committee Member); Jonathan Jacobs (Committee Member) Subjects: Agriculture; Agronomy; Biochemistry; Bioinformatics; Biology; Botany; Cellular Biology; Plant Biology; Plant Pathology; Plant Sciences

Doctor of Philosophy, The Ohio State University, 2020, Horticulture and Crop Science

An intensive production system is used to produce greenhouse floriculture crops, marketed for their flowers and attractive foliage. Chemical, environmental, and cultural methods are used to manage biotic and abiotic stresses during production. Additional tools are needed by growers because of growing concerns around the negative impact of plant production on humans and the environment. The objective of this research was to evaluate potential tools to improve floriculture crop resilience under stress during production and post-production. Botrytis cinerea causes disease in most major greenhouse crops and is resistant to several fungicides. Additional control methods, like plant growth promoting bacteria (PGPB) that can improve plant performance by increasing plant resilience to stress are needed. A collection of 60 bacterial strains was evaluated in a dual culture assay and an initial greenhouse trial with Petunia × hybrida `Carpet Red Bright' to identify strains for the biocontrol of B. cinerea. Daily flower disease severity ratings were used to select seven strains that were evaluated in the validation greenhouse trial. Three Pseudomonas strains were selected for the greatest reduction in B. cinerea infection. The efficacy of PGPB and the plant's susceptibility to B. cinerea were affected by fertilization. Petunia × hybrida `Carpet Red Bright' was treated with bacteria or a commercial biocontrol product and fertilized with synthetic chemical or organic fertilizer at a low or high rate. Measured plant growth and flower disease severity revealed that plants with the high rate synthetic fertilizer were the largest and had the lowest disease severity. Reduction of disease severity varied between bacterial and fertilizer treatment combinations. Plants treated with one bacterium had reduced disease severity at the high rate synthetic chemical fertilizer but not at the low rate organic fertilizer. Specific fertility programs provide crops with needed macro and mi (open full item for complete abstract)

Committee: Michelle Jones (Advisor); David Francis (Committee Member); Francesca Hand (Committee Member); Pablo Jourdan (Committee Member); Matthew Kleinhenz (Committee Member) Subjects: Agriculture; Horticulture