Date of Graduation

12-2019

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor

Ehsan Shakiba

Committee Member

Karen Moldenhauer

Second Committee Member

Andy Pereira

Third Committee Member

Ainong Shi

Keywords

Panicle Architecture, Plant Breeding, Plant Genetics, Plant science, QTL mapping, Rice

Abstract

Grain yield in rice consists of multiple yield components such as number of panicles/plant, number of tillers/plant, and number of seeds/panicle. Panicle architecture is an important yield trait yield as the number of seeds on a panicle greatly contributes to the overall panicle yield. A QTL analysis and mapping study on panicle architecture and yield-related traits was performed to identify major QTL and candidate genes associated with the traits. The first objective of the project was to do a yield study evaluating 15 agronomic traits between each of the four U.S. rice cultivars, ‘LaGrue’, ‘Lemont’, ‘Bengal’, and ‘Mars’, to determine which cultivars should be used in developing a bi-parental population. The results from this study showed LaGrue significantly exceeding Lemont in number of seeds produced on a panicle while Lemont had significantly longer panicles and higher 100 seed weight/panicle. LaGrue and Lemont were therefore chosen for development of a bi-parental population for the second objective of the project. The second objective was to detect major QTL for panicle architecture and yield-related traits. The study was conducted at the University of Arkansas System Division of Agriculture’s Rice Research and Extension Center in Stuttgart, AR and the Pine Tree Research Station near Colt, AR. The population was evaluated for plant height, heading date, panicle length, flag leaf length and width, number of primary panicle branches and number of secondary panicle branches. Results from QTL mapping showed two major QTL for plant height co-localized on chromosome 1 that explained a very high amount of phenotypic variation. On Chr. 8, two QTL for flag leaf length and two QTL for panicle length were detected at both locations which were co-localized in a 3.2Mbp region. A candidate gene known as Semi-dwarf 1(sd-1) was found on chromosome1 that gives rice plants a semi-dwarf height and increased lodging resistance. Six candidate genes, UBP1-5, UBP1-8, Wide and Thick Grain 1 (WTG1), OsSPL16, OsSPL14, and OsCOL15, were found to control panicle development and flag leaf development. The QTL detected would be useful for molecular breeding in the development of elite rice cultivars.

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