University of Arkansas, Fayetteville ScholarWorks@UARK Theses and Dissertations 7-2020 Genetics of Physiological Traits Associated with Drought Tolerance in Soybean (Glycine max) Sumandeep Kaur Bazzer University of Arkansas, Fayetteville Follow this and additional works at: https://scholarworks.uark.edu/etd Part of the Agronomy and Crop Sciences Commons, Cellular and Molecular Physiology Commons, and the Plant Breeding and Genetics Commons Citation Bazzer, S. K. (2020). Genetics of Physiological Traits Associated with Drought Tolerance in Soybean (Glycine max). Theses and Dissertations Retrieved from https://scholarworks.uark.edu/etd/3819 This Dissertation is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of ScholarWorks@UARK. For more information, please contact [email protected]. Genetics of Physiological Traits Associated with Drought Tolerance in Soybean (Glycine max) A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Crop, Soil, and Environmental Sciences by Sumandeep Kaur Bazzer Punjab Agricultural University Bachelor of Science in Biotechnology, 2013 Punjab Agricultural University Master of Science in Plant Breeding and Genetics, 2015 July 2020 University of Arkansas This dissertation is approved for recommendation to the Graduate Council. __________________________ Larry C. Purcell, Ph.D. Dissertation Director __________________________ __________________________ Jeffery D. Ray, Ph.D. Richard E. Mason, Ph.D. Committee Member Committee Member __________________________ __________________________ Mary C. Savin, Ph.D. Ken Korth, Ph.D. Committee Member Committee Member Abstract Soybean (Glycine max L.) is one of the major row crops in the United States, and its production is often limited by drought stress. Physiological traits from exotic germplasm that confer drought tolerance may be useful in improving commercial soybean production. For example, carbon isotope ratio (δ13C) is positively correlated with water use efficiency (WUE), 15 and nitrogen isotope ratio (δ N) is negatively correlated with N2 fixation; canopy temperature (CT) is an indicator for genetic variation in transpiration and stomatal conductance. Therefore, the objectives of this research were to identify the genomic regions associated with: (1) δ13C and 15 δ N using a population of 196 F6-derived recombinant inbred lines (RIL) from PI 416997 × PI 567201D that was phenotyped in four environments, (2) CT and δ13C using a population of 168 F5-derived RILs from KS4895 × Jackson that was phenotyped in multiple environments and irrigation treatments. In the PI 416997 × PI 567201D population, δ13C and δ15N had a wide phenotypic range in all environments, and PI 416997 had higher δ13C and lower δ15N values than PI 567201D. δ13C had high heritability (90%) whereas the heritability of δ15N was relatively lower (35%), indicating that δ15N was more affected by the environment. QTL mapping identified eight loci on seven chromosomes associated with δ13C, and these loci explained between 2.5 to 30% of the phenotypic variation. There were 13 loci on 10 chromosomes associated with δ15N, explaining 1.7 to 14.4% of the phenotypic variation. There were strong interactions between QTLs and environments for δ15N. In the KS4895 × Jackson RIL population, Jackson had a cooler canopy than KS4895, and the heritability of CT had low heritability (31%) across environments. There were 11 loci present on eight chromosomes associated with CT that individually explained 4.6 to 12.3% of the phenotypic variation. The heritability of δ13C in KS4895 × Jackson RIL population heritability was 83% when estimated over environments and over irrigation treatments. A total of 24 QTLs associated with δ13C were identified and clustered in nine genomic loci on seven chromosomes. The identified QTLs for δ13C, δ15N, and CT were co-localized with genomic regions associated with drought tolerance-related traits from previous studies. These genomic regions may be important resources in soybean breeding programs to improve tolerance to drought. Further research is needed to fine map the identified QTLs and validate markers linked with these regions . ©2020 by Sumandeep Kaur Bazzer All Right Reserved Acknowledgments I would like to thank my advisor, Dr. Larry C. Purcell, for his continued and selfless encouragement and support throughout my graduate studies. I am also very thankful for the faith that he has given me in conducting this research project. He always gave me valuable and precious advice whenever I encountered any research or personal problems. I appreciate him sharing his research experience and opinions with me. He often imparted me knowledge by example and through his dedication and passion for research. I will always keep the lessons he has taught me in mind and use them in my research career. I would also like to thank my advisory committee members: Dr. Jeffery D. Ray, Dr. Richard E. Mason, Dr. Mary C. Savin, and Dr. Ken Korth. I appreciate their understanding, precious suggestions, and patient help on my research project. Additionally, I would like to thank the members in our research group for their support: Dr. Andy King for his help with my lab, field work, and experimental design of my research project; Marilynn Davies for her help, suggestions, and her patient guidance on my research or my personal problems; Dr. Avjinder Kaler and Dr. Sadal Hwang for their help with building my research background; Caio dos Santos, Flávia Werner, Letícia Fontana, and Akshita Mishra for their help with my research work and for their friendship. I enjoyed the time working together with them, and I will never forget them. I would like to thank the Department of Crop, Soil and Environmental Sciences at the University of Arkansas for supporting my graduate studies and everyone working there. Finally, I would like to thank the United Soybean Board and the Arkansas Soybean Promotion Board for their financial support of my research project. Dedication I dedicate my dissertation to my family. My loving grandparents, Surjit Kaur and Santokh Singh, and parents, Nirmal Singh and Mohinder Kaur, who have done everything for me which I could never pay back. My sister and brother also gave tremendous support and love to me. My close friends’, Avjinder Kaler and Mohini Prabha Singh, support have given me great courage to face any difficulty and hardship in my life. And lastly, but far from least, I would like to thank my whole Bazzer family, for their support and blessing in my life. Table of Contents CHAPTER I. Introduction and Literature Review ...................................................................1 Introduction .....................................................................................................................................2 Literature Review …........................................................................................................................6 Soybean Yield and Impact of Drought ......................................................................................8 Mechanisms to Ameliorate Drought Impacts ……………….……...………………..………..9 Morphological Responses to Water Stress ….…………………....………………….…..…10 Physiological Responses of Water Stress ..............................................................................11 Breeding for Drought Tolerance ..............................................................................................12 Traits Associated with Drought Tolerance ……………………...…….................................13 Carbon Isotope Ratio .............................................................................................................13 Canopy Temperature .............................................................................................................15 Nitrogen Fixation ...................................................................................................................16 Mapping QTLs for Drought Tolerance Related Traits ............................................................18 Objectives .....................................................................................................................................21 References .....................................................................................................................................23 CHAPTER II. Identification of Quantitative Trait Loci for Carbon Isotope Ratio (δ13C) in a Recombinant Inbred Population of Soybean ........................................................................38 Abstract .........................................................................................................................................39 Introduction ...................................................................................................................................40 Materials and Methods ..................................................................................................................44 Field Experiments ………….……………...............................................................................44 Phenotypic Evaluations ............................................................................................................45 Statistical Analysis ...……………………………....................................................................46 GBS Library Construction, Genotyping and SNP Calling ......................................................48