Date of Award

5-2007

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Master of Science (MS)

Department

Botany and Plant Pathology

Advisor

Joyce E. Longcore

Second Committee Member

Seanna L. Annis

Third Committee Member

Seth Tyler

Abstract

Based on molecular phylogenetic analyses, the polyphyletic order Chytridiales, one of the four orders in the Chytridiomycota, contains several well-supported clades. One species, Chytriomyces angularis, however, does not group within the robust clades of the Chytridiales or any other chytrid order. The light-level morphology and zoospore ultrastructure of this aquatic species also differ from those of the type species of the genus Chytriomyces. I amassed nine additional pure culture isolates of soil-inhabiting chytrids with morphologies or rDNA sequences similar to C. angularis, including two isolates of C. poculatus, and studied the molecular phylogeny of these ten chytrids. Results of the Bayesian and maximum parsimony analyses of nucSSU and partial nucLSU rDNA sequences grouped the nine isolates and the type specimen of C. angularis in a monophyletic clade within the Chytridiomycota, exterior to the Chytridiaceae. I examined zoospores of two isolates by transmission electron microscopy, and determined that these isolates had ultrastructure similar to that of C. angularis. The variable morphology of four isolates compared to the two described species, C. angularis and C. poculatus, in addition to the molecular phylogeny and minor differences in their zoosporic ultrastructure supported the description of two additional species. Genetic, ultrastructural, and light-level morphological data support the establishment of the new order "Lobulomycetales," which contains the family "Lobulomycetaceae." I describe two new monospecific genera, "Maunachytrium" and "Clydaea" within this family and remove C. angularis and C. poculatus from the genus Chytriomyces and place them in the new genus "Lobulomycesr

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