Date of Award

8-2011

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Plant and Environmental Science

Advisor

Knap, Halina T

Committee Member

Ranney , Thomas G

Committee Member

Adelberg , Jeffrey W

Abstract

The genus Magnolia includes over 250 species that range in ploidy level from diploid to hexaploid. Although there is basic information on ploidy levels of various species, sampling is limited with specific cultivars and hybrids. The objective of this research was to determine relative genome sizes and relationships to ploidy levels among a diverse collection of species, hybrids, and cultivars using flow cytometry. Nuclei were extracted, stained with 4’, 6–diamidino–2–phenylindole (DAPI), and analyzed using a flow cytometer. Relative genome sizes were determined using Pisum sativum as the reference genome. Genome size was calibrated with ploidy level for species with documented chromosome numbers. Relative genome size for a given ploidy level varied significantly among most taxonomic sections, indicating it is desirable to calibrate ploidy level with relative genome size for each section separately. Within a section, relative 2C genome sizes, for a given ploidy level, had narrow ranges and could be used to distinguish between euploid levels. Genome size estimates, determined with DAPI or propidium iodide (PI) fluorochromes, varied (by 0% to 14%) as a function of species and base pair composition. Both methods were suitable for determining euploid level. Base pair composition of representative Magnolia spp. ranged from 61.6% to 63.91% AT. The results provide insights into reproductive biology, substantiation of hybrids and induced polyploids, and comparison of methods for determining genome size that will facilitate the development of improved hybrids in the future.
Growth responses to basal salt composition, cytokinins, and phenolic binding agents were investigated in a series of experiments to refine in vitro culture protocols for Magnolia `Ann' for micropropagation and plant improvement applications. Murashige and Skoog basal medium (MS), supplemented with 2 μM benzylamino purine (BAP) with no phenolic binding agent (PBA) generated a 3.2× multiplication rate. Media containing activated charcoal (AC) produced elongated microcuttings more suitable for rooting and ex vitro establishment, but AC reduced in vitro shoot proliferation. However, during subsequent rooting, microcuttings supplemented with AC in vitro had higher ex vitro rooting, compared to those without AC regardless of in vitro indolebutyric acid (IBA) concentration. Plants subcultured on _ MS media containing 1g/L AC resulted in acceptable rooting percentages, lateral root development, leaf production, and overall plant appearance and vigor during ex vitro establishment.

Included in

Horticulture Commons

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