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Title of Thesis

QTLs Conferring Root Arachitecture in an Interspecific Gossypium Hirsutum x Gossypium Barbadense Population

Author(s)

Muhammad Babar

Institute/University/Department Details
Department Of Biotechnology / Quaid-I-Azam University, Islamabad
Session
2009
Subject
Biotechnology
Number of Pages
183
Keywords (Extracted from title, table of contents and abstract of thesis)
QTLs, Conferring, Root, Arachitecture, Interspecific, Gossypium, Hirsutum, Gossypium, Barbadense, F2 Population, root-crop, breeding

Abstract
Genetic modification of the rooting system may lead to more drought tolerant upland cotton. A number of different root and physiological traits have been suggested as important mechanism of drought tolerance of cotton. This study was conducted to identify and map quantitative trait loci (QTLs) conferring root architecture in an interspecific cross Gossypium hirsutum x Gossypium barbadense population. An F2 population was developed which differed greatly in root characteristics. A genetic map covering 3190.50 cM, with 219 marker loci and 26 linkage groups, was constructed by using this F2 population. The Two F2 populations were grown in tube and pots experiments. Tap root traits (length, weight, and lateral root numbers) were evaluated. QTL analysis via composite interval mapping detected 17 QTLs, for three root traits including 3 QTLs for fresh root weight, 6 QTLs for lateral root numbers, and 2 QTLs for tap root length in tube experiment, while in pot experiment, 3 QTLs for fresh root weight and 3 QTLs for lateral root numbers were identified. Individually the QTLs accounted for 11-28% of phenotypic variation. Common QTLs were indentified for fresh root weight and lateral root numbers on chr. 18 & chr. 25 respectively, in both pot and tube experiments. The QTLs for root traits, firstly detected in Gossypium, may provide a basis for marker-assisted selection to improve productivity in root-crop breeding.

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S. No. Chapter Title of the Chapters Page Size (KB)
1 0 CONTENTS

 

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INTRODUCTION

1.1 Cotton
1.2 Gossypium: Evolution, Polyploidization and Domestication
1.3 Drought
1.4 Genetics of drought
1.5 Breeding approaches for drought tolerance
1.6 New genomic tools for cotton improvement
1.7 Roots for water supply and drought tolerance
1.8 Mapping QTLs for root characteristics
1.9 Application of molecular markers
1.10 Prospects for better exploiting the potential of root systems for drought
1.11 Objectives

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3 2 REVIEW OF LITERATURE

2.1 Cotton drought
2.2 Genetic dissection of crops under arid conditions
2.3 Mapping quantitative trait loci associated with drought tolerance
2.4 Root growth parameters and drought resistance
2.5 Mapping QTLs for root morphology

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4 3 MATERIALS AND METHODS

3.1 Parental screening
3.2 Development of mapping population
3.3 Simple Sequence Repeats (SSR) or microsatellite analysis
3.4 Poly Acrylamide Gels Electrophoresis (PAGE) for resolving microsatellite DNA fragments
3.5 Microsatellite data analysis
3.6 Amplified Fragment Length Polymorphism
3.7 Linkage map construction and QTL Mapping

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5 4 RESULTS

4.1 Screening of cotton varieties Pima S6 & M120 for root characteristics
4.2 Inter specific population development for mapping root QTLs
4.3 Correlation among the root traits in both F2 populations
4.4 Construction and characterization of inter specific linkage map
4.5 QTLs mapping for root traits in Tube and Pot experiments
4.6 Comparison of QTLs identified in both populations
4.7 Impact of selection from various environments (Dry vs Irri)

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DISCUSSION

5.1 Performance of parental lines Pima S6 (Gb) & M120 (Gh)
5.2 Analysis of phenotypic values
5.3 Polymorphismbetween parents and F2 population
5.4 Implication of segregation distortion
5.5 Genetic linkage map
5.6 Linkage groups and chromosomal assignment
5.7 QTLs analysis for Cotton roots morphological traits

5.8 Comparison of QTLs identified in both populations
5.9 Putative homoeologous QTLs
5.10 Polyploidy & phenotypic transgression for root characteristics
5.11 QTLs for drought under dry and irri environments
5.12 QTLs valuable in marker assisted selection

5.13 Conclusion

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LITERATURE CITED & APPENDICES

 

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