Dissertation
MOLECULAR CHARACTERIZATION OF TILLER NUMBER TRAIT IN WHEAT (Triticum aestivum L. em. Thell.)
Doctor of Philosophy (PhD), Washington State University
01/2015
Handle:
https://hdl.handle.net/2376/111272
Abstract
Wheat (Triticum aestivum L. em. Thell.) is an important cereal crop. Tiller number is a major yield-contributing trait in wheat, however, the physiological, genetic, or molecular mechanisms controlling tiller initiation and growth in wheat have not been studied in detail. The main goal of this study was to identify and characterize major gene(s) controlling tiller number trait in wheat. With the objective to identify a gene controlling the tiller number trait of wheat, tillering and branching related genes from other plants were used for a detailed bioinformatics analysis to find specific motifs and domains. Sequences corresponding to two different motifs were targeted for post-transcriptional gene silencing using Virus Induced Gene Silencing (VIGS). Hairpin constructs designed from motifs resulted into significant reduction in tiller number as compared to control. Based on the VIGS results, transgenic wheat lines were developed for stable silencing of the tiller gene. A 373bp sequence containing a part of the domain and variable N terminal was used in the hairpin RNAi construct. The range of gene silencing in the transgenic plants varied from 4% to 85%. The plant showing 85% reduction in gene expression produced a uniculm phenotype. Microscopic analysis of these RNAi plants showed absence or reduced bud formation in the leaf axils suggesting its role in bud initiation.
Motifs and domains identified in the tillering pathway were used as a query against wheat genome database to search a complete gene sequence in wheat. Cloning and sequencing of Wheat Tiller-1 gene resulted in three different clones with sequence similarity of more than 97% suggesting three homoeologous gene copies in the genome. Physical mapping of these copies in nulli-tetra and ditelosomic lines showed that the gene is located on the long arm of group seven chromosomes. Quantitative Real Time PCR analysis showed that this gene is expressed in root, stem, leaf, flag leaf and spike.
The applied part of my research focused on targeted use of marker-assisted selection for rapid introgression of genes and development of breeding lines. Using marker assisted background selection; two-gene imidazolinone resistance was transferred to Louise cultivar. Lines with desirable quality and yield were selected for field trials.
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Details
- Title
- MOLECULAR CHARACTERIZATION OF TILLER NUMBER TRAIT IN WHEAT (Triticum aestivum L. em. Thell.)
- Creators
- Rizwana Maqbool
- Contributors
- Kulvinder S Gill (Advisor)Diter von Wettstein (Committee Member)William F Schillinger (Committee Member)Xianming Chen (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Crop and Soil Sciences, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 121
- Identifiers
- 99900581728201842
- Language
- English
- Resource Type
- Dissertation