Title page for ETD etd-03282003-123427

Type of Document Master's Thesis
Author Abler, Steven W.
Author's Email Address sabler@vt.edu
URN etd-03282003-123427
Title Ecology and Taxonomy of Leptosphaerulina spp. Associated with Turfgrasses in the United States
Degree Master of Science
Department Plant Pathology, Physiology, and Weed Science
Advisory Committee
Advisor Name Title
Couch, H. B. Committee Chair
Baudoin, Antonius B. A. M. Committee Member
Ervin, Erik H. Committee Member
  • ITS
  • Leptosphaerulina
  • EF-1á
  • phylogenetics
  • morphology
  • turfgrass
Date of Defense 2003-01-31
Availability unrestricted
Leptosphaerulina spp. are common fungi that have been reported to colonize several turfgrass species. Controversy exists regarding the relationship of Leptosphaerulina spp. and their turfgrass hosts. The fungus has been classified as a saprophyte, senectophyte, weak pathogen, and pathogen of turfgrasses. There has also been conflicting reports regarding the delineation of species within the genus Leptosphaerulina. Because of the uncertainty regarding the ecology and taxonomy of the genus in relation to turfgrasses the present study was undertaken. The ITS and EF-1á gene regions were sequenced and analyzed to compare to the multiple taxonomic schemes reported in the literature. The ITS region offered no resolution of species; however, the phylogeny of the EF-1á gene was consistent with the six-species model of Graham and Luttrell. Inoculation experiments were performed on unstressed and artificially stressed plants to determine whether the fungi are pathogens, senectophytes, or saprophytes of turfgrasses. Perennial ryegrass and creeping bentgrass plants were stressed by placing them in a dew chamber set at 38ºC, 100% R.H., and no light for two and one days respectively. Plants were inoculated with cultures of Leptosphaerulina isolated from turfgrasses, and maintained at optimum conditions reported for infection and colonization. There was no visible difference between inoculated and uninoculated plants, and examination of cleared and stained leaves with a light microscope revealed spores that germinated and produced appressoria, but failed to penetrate the epidermal cells. The lack of infection and colonization suggests that Leptosphaerulina spp. are saprophytes of turfgrasses.
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