Date of Award

7-2014

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Plant and Environmental Science

Advisor

White, Sarah A

Committee Member

Jeffers , Steven N

Committee Member

Bridges , William C

Committee Member

Wells , Christina E

Abstract

The costs and need for clean water are increasing for greenhouse, nursery, and agricultural businesses. Runoff from irrigated agriculture and specialty crops also can take a toll on the surrounding environment, because irrigation runoff water can contain high amounts of nutrients, contaminants, and plant pathogens. To assuage the pollution contributed to runoff water and reduce the overall volume of water used, nurseries are starting to reuse irrigation runoff water. For this to be possible, the water first should be treated before reuse. Constructed wetlands are a biological treatment option that employs vegetation to collect, filter, and store runoff water. Some wetland plants may have the ability to filter pathogen propagules from runoff without becoming infected and then becoming sources of pathogen inoculum. The purpose of this study was to evaluate the susceptibility of three wetland plants in the genus Canna. (C. flaccida, C. ×generals `Carolina Pink, and C. ×generals `Bird of Paradise') to five species of Phytophthora (P. cinnamomi, P. citrophthora, P. cryptogea, P. nicotianae, and P. palmivora) that have been found in irrigation runoff water at ornamental plant nurseries. Plants were grown in Milli-Q water was amended with fertilizer and exposed to three isolates of a single species of Phytophthora. Six plants were exposed to one species of Phytophthora for each of the five species. Six plants were also grown but were not exposed to any species of Phytophthora. Zoospore presence and activity was monitored over the course of 28 days with leaf baits, and the infestation and infection of plant roots were evaluated at the end of each experiment. Roots from every Carolina Pink plant exposed to zoospores were infested, and 75% of the plants were infected. The leaf bait results for Carolina Pink plants indicated that zoospore activity did not decline during the 28 days in the presence of plants. Canna flaccida was less susceptible; 76% of the exposed plants were infested but only 23% were infected. The Bird of Paradise plants were even less susceptible to colonization by species of Phytophthora: only 33% of exposed plants were infested and 15% were infected. There was also a decline in leaf bait colonization in the presence of both Canna flaccida and Bird of Paradise plants when compared to treatment sets that contained Phytophthora only, even after plants were re-exposed to zoospores at day 14. Phytophthora cinnamomi was most successful at colonizing species of Canna plants, regardless of species or cultivar. The Carolina Pink cultivar cannot be recommended for use in constructed wetlands or vegetative buffers, because it was highly susceptible to species of Phytophthora and could potentially contribute to inoculum loads in recycled irrigation water. Canna flaccida and Bird of Paradise plants could be utilized in vegetative buffers, as they are less susceptible and seemed to help filter inocula from runoff water, as evidenced by decreased zoospore activity over time.

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