THE EVALUATION OF Cuphea pulchra AND Cuphea schumannii AS POTENTIAL NEW ORNAMENTAL CROPS FOR INTRODUCTION INTO THE FLORICULTURE INDUSTRY DISSERTATION Presented in Partial Fulfillment of the Requirements for The Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Jennifer Hrach Leopold, B.S. ***** The Ohio State University 2004 Dissertation Committee: Approved by Dr. James Metzger, Advisor Dr. Margaret McMahon ________________________ Advisor Dr. David Gardner Horticulture and Crop Science Dr. Michael Boehm Graduate Program ABSTRACT Two species, Cuphea pulchra and Cuphea schumannii, native to Brazil and Mexico respectively, were evaluated for their potential as new ornamental crops. Both species are characteristic of the genus as suffrutescent sub-shrubs bearing intensely colored orange, ribbed flowers. No information exists regarding the horticultural qualities of either species. The objectives of the current research were to evaluate the species for ornamental qualities and begin developing information pertinent to commercial production. Propagation by vegetative cutting was the most efficacious method of propagating both species. Use of a 0.1% indol-3-butyric acid rooting hormone promoted increased root development on C. schumannii stem cuttings but had no significant effect on C. pulchra cuttings. Initial greenhouse observations and the results of three consecutive years of outdoor trials demonstrated that C. schumannii possess relatively little horticultural potential, due to an indeterminate growth habit, high susceptibility to green peach aphid infestation and development of leaf intumescence under greenhouse conditions. Conversely, C. pulchra holds much promise as an annual, landscape/garden bedding plant with its compact growth habit, sustained heavy production of attractive flowers, and resistance to greenhouse and outdoor insect pests. ii Continued studies of the species evaluated methods of growth regulation, production temperature, and photoperiodic requirements for flowering. Evaluation of plants treated with chemical growth retardants daminozide, paclobutrazol, and chlormequat indicated that growth of C. schumannii can be effectively and uniformly controlled with a concentration of 5000 ppm daminozide. Evaluation of C. pulchra showed that the plant height and form can be most successfully controlled by removing the plant apex. Results of controlled environment growth chamber studies demonstrated that plants of both species were of higher quality and flowered most readily when maintained under a day/night temperature regime of 21ºC/18ºC in comparison to plants grown under a 13ºC/10ºC or 29ºC/26ºC temperature regime. A study evaluating the photoperiodic response of both species revealed that C. schumannii can be categorized as a day-neutral or a very weak facultative long-day plant, while C. pulchra is a facultative long-day plant. Preliminary investigations were performed to determine the nature of insect resistance in C. pulchra. Choice and no-choice settling assays were used to evaluate resistance to green peach aphid and revealed that resistance is due in large part (if not all) to the presence of glandular trichomes on the stem and flower surfaces. Preliminary analysis by thin layer chromatography showed that the main component of the trichome exudate was a compound(s) that co-chromatographed with acyl esters of sucrose. Acyl esters of glucose and sucrose have been shown to be the primary compounds responsible for plant resistance to insect herbivores of wild species of tomato, potato, and tobacco. iii Dedicated in Memory of Elaine R. Hrach, Ph.D. iv ACKNOWLEDGMENTS I take this opportunity to express my heartfelt gratitude to all of those who, over the last five years, have contributed to the success of this research. I wish to thank my advisor, James Metzger, for his guidance, willingness to share his wealth of knowledge, and for allowing me the opportunity to learn from my own mistakes and successes as a researcher. I thank Peg McMahon for her encouraging words and readiness to be an advisor, mentor, and role model. I also thank members of my dissertation committee, Dave Gardner who encouraged with his words “be proud of what you do” and Mike Boehm who was willing to serve as a committee member on short notice. Finally, I am most grateful to my parents Joe and Peg Hrach, and my wonderful husband Chris for their love and support of all that I do. v VITA May 29, 1977……………………………… Born – New Castle, Pennsylvania, U.S.A. 1999……………………………………….. B.S. Biology, Allegheny College 1999 – present…………………………….. Graduate Research and Teaching Associate, The Ohio State University PUBLICATIONS 1. Leopold, J.H., J.D. Metzger, and S.A. Graham. 2003. Development and evaluation of Cuphea pulchra and Cuphea schumannii as new landscape ornamentals. ISHS ACTA Horiculturae. 624: 85-91. FIELD OF STUDY Major Field: Horticulture and Crop Science vi TABLE OF CONTENTS Page Abstract…………………………………………………………………………….. ii Dedication.................................................................................................................. iv Acknowledgments...................................................................................................... v Vita…………………………………………………………………………………. vi List of Tables………………………………………………………………………. x List of Figures……………………………………………………………………….xv Chapters: 1. Review of literature………………………………………………………... 1 1.1. U.S. floriculture industry……………………………………………1 1.2. New crop research…………………………………………………..2 1.3. Evaluation of new floriculture crops………………………………..4 1.4. Cuphea……………………………………………………………... 7 1.4.1. Cuphea pulchra……………………………………………..9 1.4.2. Cuphea schumannii………………………………………....11 1.5. Issues surrounding plant acquisition………………………………..12 1.5.1. Bioprospecting……………………………………………...13 1.5.2. Convention on biological diversity…………………………13 1.5.3. Access and benefit sharing………………………………… 14 1.5.4. NBI-Ball agreement: a working example………………….. 15 1.6. Production research for a type III species………………………….. 16 1.6.1. Propagation………………………………………………… 16 1.6.2. Control of flowering……………………………………….. 19 1.6.3. Growth regulation………………………………………….. 22 1.6.4. Temperature………………………………………………... 25 1.6.5. Plant-insect interactions……………………………………. 27 1.7. Research objectives………………………………………………....31 vii 2. Initial observation of performance under greenhouse and simulated landscape conditions………………………………………... 32 2.1. Introduction…………………………………………………………32 2.2. Materials and methods……………………………………………... 34 2.2.1. Initial greenhouse observations……………………………..34 2.2.2. Outdoor Trials……………………………………………… 36 2.3 Results and discussion……………………………………………... 42 2.3.1 Initial greenhouse observations……………………………..42 2.3.2 Outdoor trials………………………………………………. 54 2.4 Conclusions………………………………………………………… 63 3. Propagative methods……………………………………………………….. 64 3.1. Introduction………………………………………………………… 64 3.2. Materials and methods……………………………………………... 66 3.2.1. Germination rates of untreated seed……………………….. 66 3.2.2. Seed embryo excision……………………………………… 67 3.2.3. Acceleration of cutting rooting with hormone treatment…... 69 3.3. Results and discussion……………………………………………... 70 3.3.1. Seed germination…………………………………………... 70 3.3.2. Seed embryo excision……………………………………… 73 3.3.3. Effect of rooting hormone on root development…………… 75 3.3.4. Effect of Hormodin®-1 on root development……………... 77 3.4. Conclusions………………………………………………………… 79 4. Preliminary investigation of the effects of temperature on growth and development…………………………………………………………… 80 4.1. Introduction………………………………………………………… 80 4.2. Materials and methods……………………………………………... 83 4.3. Results and discussion……………………………………………... 85 4.4. Conclusion…………………………………………………………. 93 5. Methods of growth regulation……………………………………………… 95 5.1. Introduction………………………………………………………… 95 5.2. Materials and methods……………………………………………... 99 5.2.1. Chemical growth retardants………………………………... 99 5.2.2. Photoselective filters………………………………………..103 viii 5.3. Results and discussion……………………………………………... 106 5.3.1. Chemical growth regulation………………………………... 106 5.3.2. Non-chemical growth regulation by photoselective filters… 125 5.4 Conclusions………………………………………………………… 128 6. Photoperiodic effects on flowering and growth……………………………. 130 6.1. Introduction………………………………………………………… 130 6.2. Materials and methods……………………………………………... 132 6.3. Results and discussion……………………………………………... 136 6.3.1. Cuphea schumannii…………………………………………136 6.3.2. Cuphea pulchra…………………………………………….. 141 6.4. Conclusions………………………………………………………… 146 7. Role of trichomes and trichome exudate in the resistance of Cuphea pulchra to green peach aphid……………………………………... 148 7.1. Introduction………………………………………………………… 148 7.2. Materials and methods……………………………………………... 154 7.2.1. Identification of trichome types……………………………. 154 7.2.2. Whole plant settling assay…………………………………. 154 7.2.3. Adult green peach aphid preference assay…………………. 157 7.2.4. Analysis of C. pulchra glandular trichome exudates………. 160 7.3. Results and discussion……………………………………………... 161 7.3.1. Identification of trichome types by SEM…………………... 161 7.3.2. Verification of deterrence by choice/ no-choice settling assay……………………………………………….. 165 7.3.3. Influence of glandular trichome exudate on green peach aphid settling…………………………………..170 7.3.4. Analysis of C. pulchra glandular trichome exudate……….. 173 7.4. Conclusions………………………………………………………… 175 8. General Conclusions………………………………………………………...178 References………………………………………………………………………….. 182 ix LIST OF TABLES Table Page 2.1 2001 Trial climate data. Average maximum