ABSTRACT WINSLOW, BENJAMIN KENT. Interspecific Hybridization and Characterization of Variegation in Ornamental Sweetpotato (Ipomoea batatas (L.) Lam.). (Under the direction of Dr. G. Craig Yencho). Sweetpotato (Ipomoea batatas (L.) Lam.) is an important food crop throughout the world and North Carolina is the top producer of sweetpotatoes in the US (NCDACS, 2011). The important contribution of sweetpotato to the global food production system is widely recognized. However, what is not generally recognized is that sweetpotatoes are also valued for their ornamental characteristics and ornamental sweetpotato (OSP) varieties have become an economically important crop in their own right. Novel OSP breeding, creating dramatic new plant types and leaf colors, has enabled sweetpotatoes to expand sales in the ornamental marketplace but there is considerable opportunity for the improvement of floral color and leaf variegation in this species. To improve these traits in future ornamental varieties, two separate breeding projects were conducted. The first breeding project was the interspecific hybridization of sweetpotato with morning glory species (Ipomoea L.). Since other species of Ipomoea have stunning floral diversity and other important ornamental traits, a series of interspecific crosses of sweetpotato with other Ipomoea species were conducted. Four hybrid families were produced with a total of 84 confirmed hybrid progeny. Sweetpotato crossed successfully with only two other closely related species, Ipomoea tabascana McDonald & Austin and I. trifida (Kunth) G.Don. Ipomoea tabascana was the most fecund paternal parent. The second breeding project involved the characterization of variegation in ornamental sweetpotato. Our large sweetpotato germplasm collection has over 100 variegated clones but only one of these variegated cultivars has been released. The major reason behind this lack of released variegated cultivars, is that the majority of the variegation that exist in our collection is not stable enough for large scale commercial production. Three distinct variegated phenotypes were chosen for analysis through phenotyping, testcrossing and physiological examination. It was revealed that each variegated phenotype arose from different mechanisms. A periclinal plastid chimera was discovered in ‘Tricolor’. ‘Okinawa’ and Sweet Caroline™ ‘Green Yellow’ were thought to have variegation controlled by transposable elements and the variegation in NCORN6712-057 may be the result of semigamy or transposon mediated anthocyanin instability. The information gathered from these clones in the creation of stable variegated cultivars future. © Copyright 2012 by Benjamin Kent Winslow All Rights Reserved Interspecific Hybridization and Characterization of Variegation in Ornamental Sweetpotato [Ipomoea batatas (L.) Lam.] by Benjamin Kent Winslow A thesis submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Master of Science Horticultural Science Raleigh, North Carolina 2012 APPROVED BY: _______________________________ ______________________________ Dr. G. Craig Yencho Dr. Dennis J. Werner Committee Chair ________________________________ ________________________________ Dr. Shyamalrau Tallury Dr. Alexander Krings DEDICATION To my mother and best friend- this thesis, as well as all of my other accomplishments in life, are dedicated to you. Without your love and guidance, this never would have happened. In loving memory: Susan Kent Winslow 1956-2012 ii BIOGRAPHY Benjamin Kent Winslow was born on May 26, 1984 in Towson, Maryland, the son of Dr. Raimond and Susan Winslow and older brother of Rebecca Winslow. He was raised in the Baltimore suburb of Timonium, Maryland, living in Webster Groves, Missouri and Golden Valley, Minnesota before returning to Maryland at the age of seven. He attended Baltimore County public schools and graduated from Dulaney High School in 2002. Horticulture fascinated Ben from an early age and his passion for gardening was nurtured by his family. Summers were spent with his four grandparents in Falmouth, Maine enjoying the outdoors and learning about gardening. It was no surprise to anyone that Ben chose to study horticulture and attended NC State University in the fall of 2002 majoring in Horticultural Science with an Agri-business minor. During his undergraduate years, Ben was an active member of the department’s ALCA team and conducted three different landscaping internships during his summer breaks. After graduation from the department in 2006, he continued to work at his grocery store produce job until joining the sweetpotato breeding and genetics project with Dr. G. Craig Yencho as a research technician in June 2007. In 2009, Ben began his M.S. degree at NC State University in sweetpotato breeding under the direction of Dr. G. Craig Yencho, while still remaining a research technician for the project. His graduate work was done on a part-time basis to allow for his full-time research technician duties with the project. After graduation, he will move to California to work as a plant breeder for Ball FloraPlant in Arroyo Grande, CA. He will focus on breeding new ornamental crops for the domestic and European markets. iii ACKNOWLEDGMENTS My journey through graduate school has been a long and winding one so I apologize in advance if I omit anyone, as there are so many people who made a positive contribution to my research. I’d like to begin by thanking my advisor, Dr. G. Craig Yencho. I am eternally grateful to you for taking a chance on me and allowing me to further myself through graduate work, even though I was not an ideal candidate. You made sure to question my assumptions and play “devil’s advocate”, which made me squirm, but also helped me grow and I am a better scientist as a result. I will always remember you “grunting” back at the hippos at Tala Game Reserve in Pietermaritzburg. I was fortunate to have a diverse, supportive, and flexible Master’s committee for my unorthodox graduate career. Dr. Denny Werner is the best teacher I have known and I am thankful for his knowledge and support for both my undergraduate and graduate career. Dr. Shyamalrau Tallury “Shyam” was always the calm voice of reason I so often needed. His talent as a cytologist is unparalleled. He graciously helped out with our lab-based research and allowed me to use his facilities and supplies. Thanks also to Dr. Alexander Krings who provided me with excellent help at data analysis that I admittedly lack. The sweetpotato breeding and genetics project has been my home for the past five years and I am deeply grateful to all of its members, past and present. Ken Pecota, also a technical adviser on my committee, is the most insightful, passionate, and intelligent breeder I have ever met and so much of what I know is because of him. I’m truly honored to be able to say thank you. Meri Reeber has been a huge help and a great friend. I’ve learned great organizational skills from her and she was right behind the tractor with me as we planted. iv Also behind that tractor with me were student employees Peyton Peterson, Austin Zanella, and Tracy Jarrell whose assistance and friendship was invaluable. Dr. Jessica Barb deserves thanks as she helped start this project with me back in 2008 by doing an excellent literature review that I expanded upon for my thesis. She helped plant the seed of interspecific work within Ipomoea that would later become part of this thesis. Thanks to Dr. Tom Ranney for allowing me to use his lab and flow cytometer at the Mountain Horticulture Crops Research and Extension Center in Mills River, NC. His technician, Nathan Lynch, provided me with expert advice and graciously ran some my remaining samples on his for me on his own time. Rachel McLaughlin, of course deserves many thanks. She is excellent at what she does and always sorted me out. The entire department of Horticultural Science is also responsible for my success and I would like to thank all of my horticulture professors and the other faculty and staff I have gotten to know in my ten year time with the department. Its diverse and comprehensive disciplines allowed me to do almost every aspect of my research in house. The staff that care for and maintain the research facilities of the Horticulture Crops Research Station, and Method Road and Horticulture Field Labs greenhouse facilities where my research was conducted are also deserving of commendation. Thanks to Dr. Janet Dow of the Flow Cytometry and Cell Sorting Laboratory, College of Veterinary Medicine at NC State University, who ran our variegated flow cytometry samples. George VanEsbroeck was also immensely helpful with the ovule culture and other lab work and was a great springboard for bouncing off breeding ideas. Dr. v Rhongda Qu and his lab technicians also graciously provided skill and materials for ovule culture. A very big thank you is due to Proven Winners who funded my research and especially to their Director of New Products, Dr. Rick Schoellhorn. Rick, you are a great friend, excellent mentor, and the best plant-geek out there. I look forward to working with you in the future. Finally, it is to my family that I am most grateful. Mom, Dad, Becky and all four grandparents provided all of the love and support I needed for a successful graduate career. I love you all. vi TABLE OF CONTENTS List of Tables ........................................................................................................................... ix List of