Date of Award

9-1-2025

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Agricultural and Environmental Sciences

First Advisor

Fulya Baysal-Gurel

Abstract

Ornamental plant production is a continuously expanding industry in the United States and worldwide. Hydrangea species are highly valued in ornamental plant production, especially bigleaf hydrangea (Hydrangea macrophylla). Powdery mildew is of particular interest on bigleaf hydrangea as there are no resistant varieties. The causal agent of powdery mildew of bigleaf hydrangea is Golovinomyces orontii (formerly Erysiphe polygoni). The goal of this research was to provide solutions for powdery mildew disease of hydrangea through improved chemical control, development of laboratory-based research systems, and identification of genes related to powdery mildew. A detached-leaf assay was developed and evaluations correlated to whole plant results, which confirmed cultivars Veitchii and Nigra were most and least tolerant to powdery mildew, respectively. Leaves from inoculated and control plants were sampled at 12 timepoints after inoculation and used for transcriptome sequencing and analysis. Differentially expressed genes (DEGs) were identified by comparing normalized read counts between ‘Veitchii’ and ‘Nigra’ at each time period in a general linear model. An average of 7678 DEGs were identified at each time point. DEGs were chosen for functional verification through RT-PCR. Genes HydATP, HydCYSPRX, and HydUBC were identified as the most significant genes based on expression patterns. Finally, a chemical control study showed that low rates and long spray intervals of the fungicide Postiva provided similar control as higher rates and shorter intervals. Together, these results provide a comprehensive framework for control of powdery mildew disease in hydrangea through current best-management practices and future development of powdery mildew resistant cultivars.

Download

Included in

Agriculture Commons

Share

COinS