Doctor of Philosophy (PhD)


Plant Environmental Management and Soil Sciences

Document Type



The southern US environment is a very conducive environment for agriculture and fisheries. Rice farming, shrimping and water related activities help drive the local economy. However, there are several factors that impede the success of these activities. Sheath blight (SB) disease caused by Rhizoctonia solani is one of the major biotic constraints to high grain yield and quality for most commercial U.S. rice varieties. Although different breeding lines with high levels of "partial resistance" have been developed none has been used directly as a commercial variety. The first research objective of this research was to identify and develop advanced breeding lines for sheath blight resistance with high grain yield and quality through traditional breeding methods. The second research objective was to identify and evaluate non-synonymous SNP markersfor SB resistance. Seven elite breeding lines showed relatively high yields vs commercial checks in inoculated field plots. The selected lined carried SNP markers within candidate genes for sheath blight resistance including a regulatory gene on chromosome 9 was shown in RNA-Seq studies to play a role in resistance. This research demonstrated that a combination of traditional breeding and genomic approaches can facilitate rapid development of elite breeding lines with high grain yield and quality traits for southern U.S. environments.

The third research objective was focused on Salvinia molesta,giant aquatic fern which invades bayous, large lagoons and lakes and is considered as a major problem to Louisiana and Texas. Genetic and phenotypic diversity study of S. molestain these locations showed a significant variation for all five morphological traits measured both within and across collection sites. Although substantial morphological and molecular variations were detected both within and among populations, all data from this study suggested that these six populations were derived originally from the same clonal or related populations. A practical implication of this result is that different and location-specific control strategies for S. molesta most likely will be needed.



Committee Chair

Oard, James H.