BIOCHEMICAL and COLORIMETRIC STUDY of FLOWER COLOR in PHLOX SPECIES THESIS Presented in Partial Fulfillment of the Requirements
Total Page:16
File Type:pdf, Size:1020Kb
BIOCHEMICAL AND COLORIMETRIC STUDY OF FLOWER COLOR IN PHLOX SPECIES THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Andres Bohorquez-Restrepo, B.S Graduate Program in Horticulture and Crop Science The Ohio State University 2015 Thesis Committee: Dr. Pablo Jourdan, Co-Advisor Dr. Joseph Scheerens, Co-Advisor Dr. Michelle Jones Copyrighted by Andres Bohorquez-Restrepo 2015 ABSTRACT Flower color is arguably the most important phenotypic feature of ornamental plants and extensive selection and breeding is done to develop new colors. Variation in flower color can be caused by different factors such as the composition and concentration of pigments, vacuolar pH and the presence of cofactors. The same color in two flowers may be the result of different mechanisms. Yet quantifying color variation can be challenging. Digital imaging coupled with analytic software is a powerful tool that can transform qualitative measurements of phenotypic characters like color and shape into quantitative data. Such a tool permits both a more objective analysis of traits that can be difficult to measure, as well as integration with molecular and biochemical data. In this study, a germplasm collection of Phlox was examined both for flower color variation as well as for anthocyanidin pigment composition. Phlox is a genus native to North America that includes an array of colorful flowers often described as purple, lilac, pink, red, orange and blue. The principal pigments of Phlox flowers are anthocyanins, but little is known about pigment variation in this genus. Tomato Analyzer (TAn) software was used to examine the variation in color from digital images of flowers of 89 Phlox accessions from the Ornamental Plant Germplasm Center. These accessions included representatives of 17 ii species distributed across the three major sections of the genus. Hierarchical cluster analysis was used to classify the flower color in the sampled population into ten different clusters based on colorimetric data. These clusters provide an objective color category system that can be used to describe the variation in flowers within Phlox. The most frequent color in the germplasm collection was the commonly described “phlox purple” or “pink”, here named Red-Purple, that could be separated into three clusters that distinguished subtle variations in lightness within this group. The Red-Purple group accounted for around 80% of the accessions and was widely distributed across the three sections of the genus. Another color cluster, named Lavender, was primarily found in numerous samples within a single section. The species with most variation in color were P.subulata, P.pilosa, P.carolina, P.ovata and P.paniculata. To complement the colorimetric analysis, anthocyanidin pigments were extracted from the flowers and the relationship between pigments and colorimetric parameters was analysed. All six main anthocyanidins (delphinidin, cyanidin, petunidin, malvidin, pelargonidin and peonidin) were found in the population. Delphinidin and cyanidin were the major anthocyanidins in most of the samples; petunidin and malvidin often co-appeared; malvidin and delphinidin were often found in an inverse relationship. Pelargonidin and peonidin were absent in the majority of samples, but the presence of pelargonidin resulted in color that identified a different cluster. Variation in lightness within the Red-Purple group of clusters coincided with fluctuations in petunidin and malvidin content. Linear regressions suggested iii petunidin may be an important component of variation in colorimetric parameters, possibly due to its relationship to malvidin and delphinidin. While general trends in anthocyanidin pattern and color were observed, different pigment composition could result in the same color, and nearly identical pigment composition could yield different colors. Thus, flower color in Phlox is only partly influenced by anthocyanidin composition and other factors play an important role. This work presents the most extensive color survey in Phlox to date, from both a biochemical and colorimetric perspective. The defined color clusters provide a useful objective system to describe flower color in the genus and facilitate more extensive characterization of an expanding germplasm collection. The anthocyanidin patterns provide a tool to identify potentially interesting parents in crosses aimed at modifying flower color. The findings provide information relevant for the study of anthocyanin biology in Phlox and for breeding improved cultivars of this important ornamental genus. iv Dedication A los Abicaru v ACKNOWLEDGEMENTS First and most important my parents Rodrigo and Amanda, for their eternal support. There are not enough words to explain how thankful I am. I love you. Ian, I also fall short in words to express my gratitude. You have been on this trip with me since the beginning, thank you for your never ending patience, love and unconditional support. Joe and Pablo, your guidance through this journey is invaluable. It warms my heart to see you guys teaching with so much passion after all these years. My colleagues and friends from the Grotewold lab: Isa, Katherine, Katja and Bettina. I guess you are all my big sisters now, thank you for your friendship and continuous support, I’ve learned quite a lot from all of you! Erich, I thank you as well for introducing me to the extraordinary world of the anthocyanins. OPGC members, you guys rock! It has been very entertaining sharing my work space and all those lunches with you guys. Special thanks to Peter (Phlox wizard), Steven, Michelle (Third committee member), Dominic and all the unsung heroes that contributed one way or another to this process. Muchisimas gracias. vi VITA March 23, 1985 ..............................................Born, Medellin, Colombia 2009 ...............................................................B.S. Biology, Universidad de Antioquia 2010-2011 ......................................................Research Assistant, Grotewold Lab The Ohio State University 2011 to present .............................................Graduate Teaching Assistant/Graduate Research Assistant, Department of Horticulture and Crop Science, The Ohio State University PUBLICATIONS Pourcel L., Irani N., Bohorquez-Restrepo A. & Grotewold E. (2012) Anthocyanin Biosynthesis, Transport and Regulation: New Insights from Model Species. In Recent Advances in Polyphenol Research, Volume 3. Wiley-Blackwell, UK. Pp. 143-154. Pourcel L., Irani N., Koo A., Bohorquez-Restrepo A., Howe G. & Grotewold E. (2013). A chemical complementation approach reveals novel genes and interactions of flavonoids with other pathways. Plant J. 74:383-397. FIELDS OF STUDY Major Field: Horticulture and Crop Science vii TABLE OF CONTENTS ABSTRACT ...................................................................................................................ii DEDICATION ...............................................................................................................v ACKNOWLEDGEMENTS ..............................................................................................vi VITA ............................................................................................................................vii LIST OF FIGURES .........................................................................................................x LIST OF TABLES ...........................................................................................................xiii Chapters: 1. Digital Imaging to Classify Phlox Flowers by Colorimetric Parameters .................1 Introduction ...................................................................................................1 Materials and Methods ..................................................................................10 Results ............................................................................................................12 Discussion.......................................................................................................15 2. Anthocyanidins in Phlox and Their Relationship to Flower Color..........................31 Introduction ...................................................................................................31 Materials and Methods ..................................................................................37 Results ............................................................................................................40 viii Discussion.......................................................................................................45 Conclusions and Future Prospects .............................................................................72 Appendices: Appendix A Colorimetric Analysis Data and Scans ........................................76 Appendix B Chromatography Data ................................................................122 Appendix C Multiple Linear Regressions in R ................................................127 Appendix D Relative Abundance and Concentration of Anthocyanidins in Minor Species ...........................................................................................................131 References .................................................................................................................135 ix LIST OF FIGURES 1.1 Representative flower color variation in Phlox. Left: range of flower shapes and