INTROGRESSION OF IMPORTANT ECONOMICAL FEATURES OF Vaccinium elliottii INTO SOUTHERN HIGHBUSH BLUEBERRY By DIEGO CABEZAS A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2019 © 2019 Diego Cabezas To my wife and children ACKNOWLEDGMENTS I thank my parents, brother and sisters for their continued support and love throughout my life, for always being there when I need them, for their example and great influence in my life. I thank my wife Constanza for her love, constant care, and patience during this path. I thank my mentor Dr. Paul Genho for turning the course of my career in a positive direction. I thank him for giving me the tools to become a better person and for showing me the beauty of plant breeding. I thank Dr. Patricio Munoz for his constant advice and patience. I will be always grateful for his example and care. I thank Dr. Paul Lyrene for his support, time and efforts to make this project possible, for dedicating the time to answer my questions. I thank Elliot Norden for preparing the materials, so I was able to undertake this study. I thank Dr. Ivone de Bem Oliveira for her friendship, constant support and advice from the beginning. I thank Ayron Utreras for his influence throughout my life and his cheerfulness. I thank the blueberry breeding family for their support and care through my master. Specially Lauren Scott and her team for the long hours they dedicated to this project. I express gratitude to my committee members, Dr. Jose Chaparro, Dr. Esteban Rios and Dr. Pam Soltis. 4 TABLE OF CONTENTS page ACKNOWLEDGMENTS .................................................................................................. 4 LIST OF TABLES ............................................................................................................ 6 LIST OF FIGURES .......................................................................................................... 7 ABSTRACT ..................................................................................................................... 8 CHAPTER 1 INTRODUCTION .................................................................................................... 10 2 EVALUATING CROSS DIRECTION FOR INTERSPECIFIC HYBRIDIZATION OF VACCINIUM ELLIOTTII AND SOUTHERN HIGHBUSH BLUEBERRY ............ 15 Background Information .......................................................................................... 15 Materials and Methods............................................................................................ 16 Results .................................................................................................................... 20 Discussion .............................................................................................................. 22 3 PHENOTYPIC DIFFERENCES BETWEEN SOUTHERN HIGHBUSH, VACCINIUM ELLIOTTII AND THEIR HYBRIDS ..................................................... 32 Background Information .......................................................................................... 32 Materials and Methods............................................................................................ 33 Results .................................................................................................................... 37 Discussion .............................................................................................................. 40 4 SUMMARY AND CONCLUSIONS .......................................................................... 53 APPENDIX CROSS DIRECTION EVALUATION FOR INTERSPECIFIC HYBRIDIZATION OF VACCINIUM ELLIOTTII AND SOUTHERN HIGHBUSH BLUEBERRY ............ 56 LIST OF REFERENCES ............................................................................................... 57 BIOGRAPHICAL SKETCH ............................................................................................ 64 5 LIST OF TABLES Table page 2-1 Number of flowers pollinated…. .......................................................................... 27 2-2 Interspecific hybridization between SHB and V. elliottii ...................................... 28 3-1 Planting year, and years of evaluation for different hybrid family types. ............. 45 A-1 Crossability in interspecific hybridization between V. elliottii and SHB ............... 56 A-2 Seed germination in interspecific hybridization between V. elliottii and SHB ...... 56 6 LIST OF FIGURES Figure page 2-1 Seedlings placed in a greenhouse. ..................................................................... 29 2-2 Fruit set for 10 reciprocal crosses between V. elliottii and V. corymbosum. ....... 30 2-3 Average seeds per berry. ................................................................................... 30 2-4 Number of seeds obtained per pollinated flower................................................. 31 2-5 Germination percentage. .................................................................................... 31 3-1 pH of families. ..................................................................................................... 46 3-2 Total Soluble Solids. ........................................................................................... 46 3-3 Soluble solids by Total titratable acids. ............................................................... 47 3-4 Fruit firmness. ..................................................................................................... 47 3-5 Fruit firmness by size. ......................................................................................... 48 3-6 Fruit diameter. .................................................................................................... 48 3-7 Total Titratable Acids. ......................................................................................... 49 3-8 Total soluble solids by size. ................................................................................ 49 3-9 Fruit size and color. ............................................................................................ 50 3-10 Plant height......................................................................................................... 50 3-11 Plant vigor........................................................................................................... 51 7 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science INTROGRESSION OF IMPORTANT ECONOMICAL FEATURES OF Vaccinium elliottii INTO SOUTHERN HIGHBUSH BLUEBERRY By Diego Cabezas December 2019 Chair: Patricio Munoz Major: Horticultural Sciences Vaccinium elliottii is a wild diploid blueberry species relative to the tetraploid cultivated, Vaccinium corymbosum. This wild species possesses important horticultural traits that can contribute to enhance fruit quality and adaptation to the Florida’s environment. The ultimate goal of this study was to generate information towards introgressing favorable traits from V. elliottii into southern highbush blueberry (SHB). Two studies were performed, the first one consisting of evaluating the effect of cross direction on interspecific hybridizations between V. elliottii and SHB. For this, ten synthetic autotetraploid genotypes of V. elliottii derived from colchicine treatment were used as both male and female parents in distinct crosses with SHB. The results showed that when SHB was used as the female parent, significantly more berries were produced per pollinated flower compared to when V. elliottii was the female parent. However, a significant decrease in the average number of seeds per berry was detected when SHB as used as female parent. Overall, it was found that V. elliottii can be successfully hybridized with cultivated SHB in both directions, and that direction of the cross had a small effect on number of seeds per pollinated flower or on germination percent. The second project aimed at evaluating different stages of breeding using V. 8 elliottii. For this, the performance of genotype crossing combinations was evaluated in terms of fruit quality traits as fruit size, firmness, acidity, brix⁰, weight, and color, considering different breeding generations (i.e., F1, F2, and BC1). The results showed an increase in berry size on F1, F2, and BC1 berries when compared with V. elliottii, while F1 and F2 showed a decrease in size when compared to SHB berries. The highest levels of soluble solids, an indicator of sugar content, were detected in V. elliottii when compared to SHB, F1, F2, and BC1. SHB and BC1 families planted in the 2017 nursery had significantly lower acidity compared with V. elliottii. No significant differences in firmness were found between hybrids, SHB, and V. elliottii. Overall, fruit quality in BC1 hybrids increased when V. elliottii was introgressed into SHB. Overall results confirm the potential of exploiting interspecific hybridization between SHB and synthetic tetraploid V. elliottii in blueberry breeding. Genetic gains can be achieved independent of the direction of crossing. The evaluation of hybrid populations showed that fruit quality increased when V. elliottii is introgressed into SHB. In addition, a large amount of variability was obtained, generating material to be exploited by the University of Florida Blueberry Breeding Program. Therefore, these results provide essential information towards the introgression of important