Doctor of Philosophy (PhD)



Document Type



Coastal erosion and wetland deterioration are serious and widespread problems affecting Louisiana’s coastal zone. The application of agronomic and molecular techniques for improving crop species is well documented. However, these have not been routinely applied to species of ecological and environmental value. Spartina alterniflora is used extensively for shoreline protection and tidal marsh restoration because of its aggressive spreading habit and tolerance to salinity. The progress of marsh revegetation projects is limited by the costs and labor associated with vegetative propagation of Spartina. Hence, a breeding program was initiated to develop improved smooth cordgrass accessions with superior seed producing ability to accelerate coastal restoration projects by developing a seed-based propagation. The objectives were to: 1) evaluate the variation among the accessions collected from South Louisiana S. alterniflora native populations, and characterize accessions selected for use in genetic improvement; and 2) assess variability at the molecular level among selected plants used to establish a breeding program. One hundred twenty-six accessions of S. alterniflora were collected across South Louisiana in 1998. The accessions were characterized for location, date of collection, seed weight, and percent germination. Biplot and cluster analysis were used to analyze patterns of variation among accessions and locations. Vegetative and reproductive traits were evaluated during the growing seasons. Significant differences occurred among accessions for traits measured during vegetative stage and days to first panicle emergence. Date of collection contributed to overall variation among accessions, reflecting differences in maturity at the time of collection. Vegetative growth and differences in rust reaction allowed characterization of S. alterniflora accessions. Positive correlations were observed among vegetative traits, and negative correlations between those traits and rust reaction. Seven superior genotypes were selected for future population improvement. To assess genetic diversity within and between superior accessions, molecular and phenotypic characterizations were used to compare 40 selected genotypes, which were subjected to DNA fingerprinting using RAPD and AFLP. Cluster analysis results revealed considerable natural variation among the original collections for traits contributing to plant establishment from seed. The differences in clustering pattern demonstrate the usefulness of molecular markers in assessing genetic diversity more accurately.



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Committee Chair

Stephen Harrison



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