Date of Graduation

12-2012

Document Type

Thesis

Degree Name

Master of Science in Horticulture (MS)

Degree Level

Graduate

Department

Horticulture

Advisor

Jon T. Lindstrom

Committee Member

John R. Clark

Second Committee Member

J. Brad Murphy

Third Committee Member

Ashley P. Dowling

Keywords

Biological sciences; Agavoid; Asparagaceae; DNA barcoding; Manfreda; Systematics; Taxonomy

Abstract

The genus Manfreda Salisb. of Asparagaceae is a genus of potential horticultural interest and is currently subject to breeding efforts at the University of Arkansas. A lack of taxonomic clarity however undermines the classification of potential inter - and intrageneric hybrids. The study aims to assess existing species delimitation within the genus Manfreda employing morphology while investigating the potential utility of Consortium for the Barcode of Life Plant (CBOL) DNA Barcodes for identification of specific taxa and an External Transcribed Spacer (ETS) - Internal Transcribed Spacer (ITS) DNA barcode for developed hybridized taxa.

Observation of 855 herbarium specimens facilitated phylogenetic and Principal Component Analysis of morphology. Phylogenetic analysis employing Maximum Parsimony and Bayesian techniques of qualitative characters failed to identify any interspecific relationships with sufficient confidence. Principal Component Analysis identified 14 species exhibiting uniformity in categorical characters. The residual seven were subjected to further review employing existing literature, biogeographical and morphological data from herbarium specimens. The study supported specific designations of 19 of 21 species studied. A proposal for Manfreda pubescens (Regel & Ortgies) Verh.-Will. ex Espejo & López-Ferr. to be relegated to a varietal rank of Manfreda maculata (Mart) Rose was concluded based on a lack of consistent derived characters as well as biogeographical and ecological continuity.

Utility of the CBOL Plant DNA Barcode for identification of Manfreda species was investigated employing phylogenetic and nucleotide networking techniques. The CBOL Plant DNA Barcode failed to identify any interspecific relationships via Maximum Parsimony or Bayesian techniques. Sufficient variation however was available for differentiation of each species of Manfreda via composition of a nucleotide network map. Results allude to minimal divergence between species of Manfreda, yet sufficient derived characters for functionality of CBOL Plant DNA Barcodes.

Analysis of an ETS - ITS DNA barcode for identification of intergeneric hybridized taxa of Agave L., Manfreda and Polianthes L. could not be conducted due to inefficiencies in DNA amplification techniques. The ETS gene region could not be amplified, a trial of three different amplification parameters was conducted and a lack of appropriate PCR primers was identified as the cause of no amplification. Amplification of the ITS gene region was successfully achieved; however, subsequent analysis of the electropherogram alluded to intra-individual polymorphisms within the genome. Therefore,it was concluded that the utility of the ITS region is negligible for DNA barcoding of the maag 01-07-13, mapo 01-04-07 and mapo 05-04-02 intergeneric hybrids.

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