Theses and Dissertations


Xin YeFollow

Issuing Body

Mississippi State University


Shaun R. Broderick

Committee Member

Richard L. Harkess

Committee Member

Guihong Bi

Committee Member

Zhaohua Peng

Committee Member

Sorina C. Popescu

Date of Degree


Original embargo terms

Complete embargo for 1 year

Document Type

Dissertation - Open Access



Degree Name

Doctor of Philosophy


College of Agriculture and Life Sciences


Department of Plant and Soil Sciences


We evaluated the genetic diversity of Penstemon's Centromeric Histone 3 (CENH3), which localizes to chromosome centromeres in eukaryotes. From RNA extractions of 56 species, we successfully amplified two CENH3s (termed CENH3a and CENH3b), which share approximately 69% sequence homology across the length of the gene and about 85% across the histone fold domain (HFD). CENH3a is generally 72 bp longer than CENH3b and contains seven exons while CENH3b is made of five. Unlike studies of CENH3 in other plants, Penstemon's CENH3 N-tail was found to be highly conserved, indicative that the genus has undergone a short evolutionary history. Surprisingly, of the 99 CENH3 sequences obtained during this study, 32 appeared to be mis-spliced and contained premature stop codons. Of those aberrant transcripts, 84.4% originated from CENH3b genomic DNA. Most mis-spliced transcripts resulted from the retention of all or part of an intron. In some cases, all or portions of an exon were missing, including one that was missing the L1 motif. Second, we systematically cataloged interspecific breeding data in Penstemon, on which we then conducted a network analysis. The resulting network provides breeders with a better visualization of successful parental combinations and also identifies gaps in interspecific breeding. This method allowed for the identification of species with a high degree of interspecific compatibility, which we compared to the CENH3 sequencing data. Finally, we studied the performance of soil streaming in high tunnel production of tomatoes (Solanum lycopersicum L.). Our experiments revealed that soil steaming and mulch reduced weed coverage of Palmer amaranth (Amaranthus palmeri S. Watson), large crabgrass (Digitaria sanguinalis L.), and yellow nutsedge (Cyperus esculentus L.). Steam and mulch increased the tomato plant size, fruit size, fruit number, and fruit yield. Additionally, soil steaming reduced tomato southern blight, caused by Sclerotium rolfsii, by 5.8-fold. These findings provide promising results for high tunnel tomato producers, particularly those involved in organic production where pesticide and fumigation use is limited.


Funding was provided in part by the Mississippi Agricultural and Forestry Experiment Station Special Research Initiative, and by the USDA National Institute of Food and Agriculture, Hatch project #1006346, and Hatch project 1023679.