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Evaluating Ethylene Sensitivity Using Mature Plant Screens and the Seedling Hypocotyl Response

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Evaluating Ethylene Sensitivity Using Mature Plant Screens and the Seedling Hypocotyl Response Evaluating Ethylene Sensitivity Using Mature Plant Screens and the Seedling Hypocotyl Response THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Nichole Frances Edelman, B. A. Graduate Program in Horticulture and Crop Science The Ohio State University 2013 Master's Examination Committee: Dr. Michelle L. Jones, Advisor Dr. Pablo Jourdan Dr. Claudio Pasian Copyrighted by Nichole Frances Edelman 2013 Abstract Ethylene (C2H4) is a gaseous hormone produced by plants in response to environmental stress and during growth and development. Sensitive seedlings exposed to ethylene gas will exhibit an exaggerated apical hook, thickened hypocotyl, and reduced hypocotyl elongation. Collectively these symptoms are known as the triple response, and have been used as a screen to identify ethylene mutants. Exposure to ethylene gas at the mature plant stage can induce flower, bud, or leaf abscission, flower senescence, leaf chlorosis (yellowing), or leaf epinasty (downward curvature). Sensitivity can vary between species and by developmental stage or tissue (flower vs leaf). Ethylene can damage plants during production, shipping, and retailing. The objectives of this research were 1) to determine if the seedling hypocotyl elongation screen could be used to predict the sensitivity of mature plants at the marketable stage; 2) to identify ethylene sensitivity differences (levels of sensitivity and symptoms) between accessions within Solanaceae; and 3) to identify ethylene sensitivity differences at different developmental stages (seedling, juvenile, and mature plants). Seedlings were germinated on filter paper saturated with 1- aminocyclopropane-1-carboxylic acid (ACC) and sensitivity was determined based on the hypocotyl lengths relative to the control (0 µM ACC). Mature plants were treated with 10 µL·L-1 ethylene gas for 24 hours, and the severity of the response was used to ii classify ethylene sensitivity. The first experiment evaluated 18 bedding plant species while the second evaluated 40 Solanaceous accessions. A classification of low, medium or high sensitivity to ethylene was assigned to plants at both developmental stages. The results showed that the seedling hypocotyl elongation screen did not consistently predict mature plant sensitivity. Ethylene sensitivity varied between species and cultivars within the Solanaceae family, and sensitivity also varied by developmental stage. Information from this research can be used by growers to identify nonresponsive or low ethylene sensitive varieties for long-distance shipping and to identify medium to highly sensitive varieties that would benefit from treatment with ethylene inhibitors (1-MCP). Plant breeders and scientists can also use this information to identify breeding lines with lower ethylene sensitivity. iii Acknowledgments I would first like to thank my advisor, Dr. Michelle Jones without whose amazing guidance and support none of this would have been possible. I would also to thank the other members of my student advisory committee, Dr. Pablo Jourdan and Dr. Claudio Pasian for their suggestions on research and critical review of the chapters. I would like to thank the members of my lab including Laura Chapin, Eileen Ramsay, Shaun Broderick, and previous member Cassi Sewell for support, technical and statistical assistance, and review of my chapters. I would also like to thank Dr. David Francis for statistical advice. I would like to acknowledge the Ohio Agricultural Research and Development Center (OARDC), and The Ohio State University D. C. Kiplinger Floriculture Endowment for funding and supporting this research. I would also like to acknowledge Ball Horticulture Company and Green Circle Growers for providing seeds and cuttings used in the experiments. Last, I would like to thank my parents and friends for their support and love, and to those who encouraged me in my career goals and furthering my education. With their help and support I had to courage to keep pursuing my goals. iv Vita 1999-2004 ......................................................Euclid High School 2004-2005 ......................................................Notre Dame College 2005-2008 ......................................................B. A. Biology, Hiram College 2011 to present ..............................................Graduate Research Associate, Department of Horticulture and Crop Science, The Ohio State University Publications Michelle Jones and Nichole Edelman. 2013. How to prevent ethylene-related losses during the postproduction care and handling of crops. Greenhouse Management. Fields of Study Major Field: Horticulture and Crop Science v Table of Contents Abstract ............................................................................................................................... ii Acknowledgments.............................................................................................................. iv Vita… .................................................................................................................................. v List of Tables ..................................................................................................................... ix List of Figures ..................................................................................................................... x Chapter 1: Introduction ....................................................................................................... 1 History of Ethylene ......................................................................................................... 1 Ethylene Synthesis .......................................................................................................... 3 Ethylene Signaling and Perception ................................................................................. 4 Plant Responses to Ethylene ........................................................................................... 7 Importance of Ethylene in the Horticulture Industry .................................................... 11 Ethylene Inhibitors ........................................................................................................ 13 Chapter 2: Comparative Evaluation of Seedling Hypocotyl Elongation and Mature Plant Screens for Determining Ethylene Sensitivity in Eighteen Bedding Plant Species .......... 19 Abstract ......................................................................................................................... 19 vi Introduction ................................................................................................................... 20 Materials and Methods .................................................................................................. 23 Seedling Hypocotyl Elongation Screen .................................................................. 23 Plant Culture for Mature Plant Screen .................................................................. 24 Mature Plant Ethylene Treatment .......................................................................... 25 Statistical Analysis ................................................................................................. 26 Results ........................................................................................................................... 26 Ethylene Sensitivity of Seedlings ............................................................................ 26 Ethylene Sensitivity of Mature Plants .................................................................... 28 Classification of Seedling and Mature Plant Ethylene Sensitivity ......................... 30 Discussion ..................................................................................................................... 31 Chapter 3: Evaluating Ethylene Sensitivity within the Family Solanaceae at Different Developmental Stages ....................................................................................................... 62 Abstract ......................................................................................................................... 62 Introduction ................................................................................................................... 63 Materials and Methods .................................................................................................. 66 Plant Materials ....................................................................................................... 66 vii Seedling Hypocotyl Elongation Screen .................................................................. 67 Plant Culture for Mature Plant Screen .................................................................. 67 Mature Plant Ethylene Sensitivity Screen .............................................................. 68 Evaluation of Tomatoes at Two Developmental Stages ......................................... 70 Statistical Analysis ................................................................................................. 70 Results ........................................................................................................................... 70 Ethylene Sensitivity within the Solanaceae Family ................................................ 71 Evaluation of Tomatoes at Two Developmental Stages ......................................... 70 Discussion ....................................................................................................................
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