THE DEVELOPMENT OF THE MODERN STRAWBERRY (FRAGARIA X ANANASSA): PHYSIOLOGY, BIOCHEMISTRY AND MORPHOLOGY OF PROGENITOR SPECIES (F. VIRGINIANA AND F. CHILOENSIS) AND RESULTING CULTIVARS A Dissertation Presented to the Faculty of the Graduate School of Cornell University In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy by Rebecca M Harbut August 2009 © 2009 Rebecca M Harbut THE DEVELOPMENT OF THE MODERN STRAWBERRY (FRAGARIA X ANANASSA): PHYSIOLOGY, BIOCHEMISTRY AND MORPHOLOGY OF PROGENITOR SPECIES (F. VIRGINIANA AND F. CHILOENSIS) AND RESULTING CULTIVARS. Rebecca M Harbut, Ph. D. Cornell University 2009 The cultivated strawberry (Fragaria x ananassa) in the northeastern United States has seen limited improvement in yield over the past century. Narrow germplasm diversity has been suggested to be a possible limitation and has resulted in evaluation of the progenitor species: F. chiloensis and F. virginiana for desirable characteristics. One of the possible avenues explored to improve the productivity of the cultivated strawberry is to increase the photosynthetic capacity through the use of F. chiloensis which has a high photosynthetic capacity. Previous research has relied exclusively on gas exchange data to quantify photosynthetic capacity; however, due to the complexity of regulatory processes that influence gas exchange it is difficult to identify the basis of the different gas exchange rates observed. Evaluation of the strawberry cultivar ‘Jewel’ and the two progenitor species was conducted to determine the basis of the observed differences in photosynthetic capacity. Results of this research suggest that the high photosynthetic capacity of F. chiloensis may be a based on higher light use efficiency, determined by chlorophyll fluorescence, and increased activity of key enzymes of the Calvin Cycle. As these photosynthetic parameters are based on gene expression, these higher rates may be genetically heritable. In order to determine the most effective use of the wild species to improve the cultivated strawberry, a field study of cultivars released during the last century was established to evaluate changes in horticultural and physiological characteristics that have occurred and to identify possible limitations to productivity. Results indicated that limited changes have occurred in carbon allocation patterns and photosynthetic characteristics and suggest that there may be opportunity to increase the productivity through altering carbon allocation patterns and increasing fruit number. The lack of change in photosynthesis suggests that improving photosynthetic capacity of the cultivated strawberry may lead to increased productivity. Further research evaluating hybrids of F. chiloensis and the cultivated strawberry may allow us to better exploit this characteristic. BIOGRAPHICAL SKETCH I grew up in beautiful British Columbia surrounded by mountains, ocean and berries. I started my plant science degree at UBC and then transferred to the Department of Plant Science at the University of Guelph where I completed my undergraduate degree and got turned on to the wonderful world of fruit by my advisor, Dr. Al Sullivan with whom I completed my masters degree. In 2004 I moved to Ithaca to start my PhD in berry crops with Dr. Marvin Pritts. I will be continuing my academic pursuits in the fruit realm in the Department of Horticulture at the University of Wisconsin-Madison. iii ACKNOWLEDGMENTS When I started my academic career I had no idea how many people would invest their time and efforts into my pursuit; and in retrospect I am amazed at the extent to which people have gone to make this experience as rewarding as it has been. I am extremely grateful for the opportunity to have had Marvin Pritts, as my advisor. He has been a mentor to me in matters of science, teaching, community service and has become a good friend. He will always be my benchmark of what a great horticulturist is. Despite having no experience in biochemistry when starting this degree, Lailiang Cheng was willing to take me on as a student and invest the time to develop my skills in biochemistry. I would also like to thank Tom Owens, an excellent teacher who always had an open door and Arthur Wilson, my guide through the fascinating world of education! Such an endeavor would not be possible without the support of great friends and family. The friendships I have made during my time at Cornell have made this experience rich and I know I have gained friends for life. Despite the great distance, my family has been a constant source of encouragement and I have appreciated all of their visits, pep talks and prayers! I can confidently say that this degree would never have been completed without my best friend and greatest supporter, Matt, who has poured so much of himself into this effort. He has allowed me to do things I would never have done on my own and kept me sane and laughing the whole way through. And of course my little Sofia who came along for the last leg of the race with me and has made the finish line sweeter than I could have ever imagined it would be! iv TABLE OF CONTENTS BIOGRAPHICAL SKETCH………………………………………..………….iii ACKNOWLEDGEMENTS.…………………………………………..………..iv LIST OF FIGURES……………………………………………………………viii LIST OF TABLES………………………………………………………………x CHAPTER 1 ................................................................................................................................ 1 THE RELATIONSHIP BETWEEN LEAF N STATUS AND PHOTOSYNTHETIC CHARACTERISTICS OF FRAGARIA X ANANASSA ‘JEWEL’........................................................ 1 INTRODUCTION.......................................................................................................................... 1 MATERIALS AND METHODS ...................................................................................................... 3 RESULTS ................................................................................................................................... 6 Growth Analysis. ....................................................................................................................... 6 Gas Exchange and Chlorophyll Fluorescence. ......................................................................... 8 Enzyme Activity. ...................................................................................................................... 10 Non-structural carbohydrates. ................................................................................................ 12 DISCUSSION ............................................................................................................................ 14 REFERENCES ....................................................................................................................... 21 CHAPTER 2 .............................................................................................................................. 26 UNDERSTANDING THE BASIS OF DIFFERENCES IN PHOTOSYNTHETIC CHARACTERISTICS OF THE PROGENITOR STRAWBERRY SPECIES F. VIRGINIANA AND F. CHILOENSIS. ............................................................................................................................ 26 INTRODUCTION........................................................................................................................ 26 v MATERIALS AND METHODS .................................................................................................... 28 RESULTS ................................................................................................................................. 31 Gas Exchange and Chlorophyll Fluorescence. ....................................................................... 33 Photosynthetic Enzymes .......................................................................................................... 34 DISCUSSION ............................................................................................................................ 37 REFERENCES ........................................................................................................................ 46 CHAPTER 3 .............................................................................................................................. 61 WITHIN SPECIES VARIABILITY OF GROWTH AND PHOTOSYNTHETIC CHARACTERISTICS OF F. CHILOENSIS AND F. VIRGINIANA ................................................. 61 INTRODUCTION........................................................................................................................ 61 MATERIALS AND METHODS .................................................................................................... 62 RESULTS ................................................................................................................................. 65 Growth Analysis. ..................................................................................................................... 65 Photosynthetic Data. ............................................................................................................... 67 DISCUSSION ............................................................................................................................ 70 SUMMARY ............................................................................................................................... 73 REFERENCES ........................................................................................................................... 74 CHAPTER 4 .............................................................................................................................