| The overall goal of this research was to use an integrated approach of molecular, cytological, and genetic methods to study and characterize forage bermudagrasses (Cynodon spp.) and cotton (Gossypium spp.) genomes. Forage bermudagrasses were characterized as a small genome ranging from 2.08 x 109 to 2.629 x 10 9 bp. Results using flow cytometry successfully classified the ploidy levels of some selected varieties. However, due to confounding effects in the DNA content, the ploidy levels of some ecotypes could not be determined.;Four PCR-based DNA fingerprinting techniques, Amplified Fragment Length Polymorphism (AFLP), Chloroplast-specific Simple Sequence Repeat Length Polymorphism (CpSSRLP), Random Amplified Polymorphic DNA (RAPD), and Minisatellite Amplified Fragment Length Polymorphism (MAFLP) were used to compare different DNA-based technologies and evaluate genetic relationships among the forage bermudagrasses. Genetic relationships within the 31 forage bermudagrasses were determined using total of 472 polymorphic markers generated by 15 AFLP, 10 CpSSRLP, 10 RAPD and 10 MAFLP primers or primer pairs. Results from the present study indicated that forage bermudagrasses have a narrow genetic base, ranging from 0.60 to 0.97. The AFLP technique provided the highest number of DNA markers, allowing a high-resolution genotyping from all lines or materials. Several ecotypes were found to be unique and some others showed close relationships to known varieties.;Novel methods of Simple Sequence Repeat Length Polymorphism (SSRLP) and AFLP differential display techniques were developed to identify transcripts associated with cyt-V, a cytoplasmic mutant in cotton. Ultrastructural observations using Transmission Electron Microscopy (TEM), chlorophyll and carotenoid contents, chloroplast protein profiles, transcript patterns and chloroplast-specific DNA markers revealed the location of cyt-V on the chloroplast genome. In another study, SSRLP markers were used to construct a genetic linkage map from an F2 population developed from the crosses of Texas Marker-1 (TM-1), a genetic standard line in Upland cotton and Ligon Lintless-1 (Li1), a mutant Upland cotton with pleiotropic effects producing only short fibers and distorted leaves. A total of 5 SSR loci were found linked with the Li1 locus. Molecular mapping results also demonstrated that the Li1 locus was located in the short arm of chromosome 22 based on analysis of chromosome-deficient cytogenetic stocks. |
