Date of Award

8-2009

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Plant and Environmental Science

Advisor

Jeffers, Steven N.

Committee Member

Kerrigan , Julia L.

Committee Member

Bridges, Jr. , William C.

Abstract

This project was composed of two separate studies. In one study, the species of Phytophthora that have been found associated with diseased floriculture crops in South Carolina and four other states were characterized and identified using molecular (RFLP fingerprints and DNA sequences for ITS regions and cox I and II genes), morphological (sporangia, oogonia, antheridia, oospores, and chlamydospores), and physiological (mating behavior and cardinal temperatures) characters. In addition, sensitivity to the fungicide mefenoxam was determined. In all, 87 isolates from 63 host plants that were collected over a 13-year period (1996 through 2008) were examined. Host plants came from 46 genera in 24 families. Seventy-four isolates came from plants grown in 16 counties in South Carolina, and 13 isolates came from plants grown in four other states: Maryland, New York, North Carolina, and Virginia. In all, 12 different species of Phytophthora were identified--including ten known species and two previously undescribed and potentially new species. The known species were: P. nicotianae(26 isolates), P. cinnamomi (14 isolates--including one isolate of P. cinnamomi var. parvispora), P. palmivora (13 isolates), P. drechsleri (10 isolates), P. cryptogea (8 isolates), P. citrophthora (4 isolates), P. citricola (4 isolates), P. capsici (2 isolates), P. tropicalis (1 isolate), and P. megasperma (1 isolate). Based on molecular and morphological characters, four isolates appeared to belong to previously undescribed and potentially new species. Fifty-eight of the host-pathogen associations investigated have not been reported previously and are new records. In the second study, a pre-plant sanitation treatment with 10% household bleach (i.e., 0.6% NaOCl) was applied to dormant bare-root daylily and hosta plants, and the effects on subsequent plant growth and development were determined. Plants were soaked for 0, 1, 5, and 10 minutes, rinsed in tap water, planted in pots, and grown for 40 to 56 days. These treatments proved to be safe to use. Plants that were soaked in bleach solution for 1 to 10 minutes before planting grew just as well as plants that were not soaked in bleach solution, and no evidence of deleterious effects on plant growth and development was found.

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