Date of Award:

5-1-1995

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Biology (Molecular Biology)

Committee Chair(s)

Elizabeth Hood

Committee

Elizabeth Hood

Committee

Noelle Cockett

Committee

Paul Wolf

Abstract

Amaranthus is a genus containing approximately 60 species, of which three are cultivated because their seeds exhibit a high protein content compared to the traditional monocot grains. Many wild Amaranthus species possess agriculturally desirable traits like drought and salt tolerance, and pathogen resistance. A phylogenetic tree of the genus Amaranthus was constructed in order to elucidate the relationships between the wild and cultivated Amaranthus species for breeding purposes in order to establish amaranth as a valuable alternative dry-land crop. Our tree was based upon restriction site analysis of two chloroplast DNA regions and a nuclear DNA region. The chloroplast regions consisted of 1) an intergenic spacer in transfer RNA genes and 2) the ribulose-1,5-bisphosphate carboxylase gene followed by an open reading frame. The nuclear region was the internal transcribed spacers (ITS) 1 and 2 flanking the 5.8S gene in the ribosomal DNA. These regions were amplified by the polymerase chain reaction and digested with a total of 38 restriction endonucleases. Eleven phylogenetically informative restriction site mutations and seven size polymorphisms among the 30 Amaranthus species making up the ingroup were noted. The heuristic search was used to determine the most parsimonious tree for each separate data set (chloroplast, nuclear, and insertional) and for two combined matrices (chloroplast/nuclear and all data sets). Overall, there was a low level of variation among the 30 species (14% polymorphic restriction sites) generating unresolved trees and suggesting a recent evolution for Amaranthus. Between-data-set congruence was evaluated to examine the accuracy of the combined trees, which revealed that the chloroplast and nuclear data sets were congruent but the insertional data set was not. Similarity between all data sets was represented by three species groupings. In addition, the molecular phylogeny provides a basis for selection of breeding pair for crop development. The phylogeny also suggests that drought tolerance evolved independently numerous times, and as a result, may be controlled by genes under strong selection pressure.

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