All praise belongs to Allah, Lord of the world, the Most Gracious and the Most Mercifull, Master of the day of the Judgement, You (Alone) we worship and you (Alone) we ask for help (for each and everything), guide us to the Straight Way, The Way of those on whom You have bestowed Your Grace not of those who earned You Anger nor of those who went astray [Al-Fatiha]. Promotor: Prof. dr. ir Marie-Christine Van Labeke Ghent University, Faculty of Bioscience Engineering Departement of Plant Production, Belgium. Dean: Prof. dr. ir. Marc Van Meirvenne Rector: Prof. dr. Anne De Paepe MORPHOLOGICAL, ECOPHYSIOLOGICAL AND BIOCHEMICAL RESPONSES TO SALT STRESS IN EGGPLANT (SOLANUM MELONGENA L.) Sami Hannachi Thesis submitted in fulfillment of the requirements for the degree of Doctor (PhD) in Applied Biological Sciences Nederlandse titel: Morfologische, ecofysiologische en biochemische reacties op zoutstress bij aubergine (Solanum melongena L.) Hannachi, S. (2016) Morphological, ecophysiological and biochemical responses to salt stress in eggplant (Solanum melongena L.). PhD Thesis, Ghent University, Ghent, Belgium. ISBN-number: 978-90-5989-893-6 The authors and promotor give the authorization to consult and to copy parts of the work for personal use only. Every other use is subject to the copyright laws. Permission to reproduce any material contained in the work should be obtained from the author. Members of the jury Promoter: Prof. dr. ir Marie-Christine Van Labeke Department of Plant Production, Ghent University, Belgium. Chairman: Prof. dr. ir. Geert Haesaert Department of Applied Biosciences, Ghent University, Belgium. Examination committee: Prof. dr. ir M’barek Ben Naceur Head of National Bank of Genes of Tunisia, Ministry of Agriculture, Tunisia. Dr. Angelo Signore Department of Agro-Environmental and Territorial Sciences, University of Bari "Aldo Moro", Italy. Prof. dr. ir. Kathy Steppe Department of Applied Ecology and Environmental Biology, Laboratory of Plant Ecology, Ghent University, Belgium. Prof. dr. ir. Stefaan Werbrouck Department of Applied Bioscience, Ghent University, Belgium. Acknowledgements Thanks ALLAH for helping me completing this work. Without his guidance, this work would never have been accomplished. I would like to express my deep gratitude to my supervisor Prof. dr. ir. Marie-Christine Van Labeke for accepting me as her Ph.D student, for her competent supervision, continuous support and for her invaluable help in my private life in Belgium. I cannot imagine a better supervisor. Her excellent academic guidance, her warm personality, and her friendship to all foreign students have encouraged me and furthered my development as a scientific researcher. I am very much indebted for her valuable suggestions and intensive help during the preparation of this dissertation, for her ability to freely discuss / open minded attitude during discussion and constructive criticism in editing the manuscript. I would also like to convey my gratitude to the jury members prof M. Ben Naceur, dr. A. Signore, prof. Katy Steppe and prof. S. Werbrouck for agreeing to participate in putting the final hand to this work through their constructive comments that improved the final version of the thesis. I would also like to most sincerely thank all my colleagues and technical staff at the lab of Horticulture and In Vitro Biology, Department of Plant Production, Faculty of Bioscience Engineering, Ghent University for their understanding, valuable advice and most of all friendship, which helped me to make it through all difficult situations. I wish to thank also Prof. dr. ir. Kathy Steppe, dr. ir. Ingvar Bauweraerts and all the staff of the Laboratory of Plant Ecology, for providing me the “LiCor-6400”, for their kindness and assistance. I would like to thank the Tunisian government (Alternating Scholarship) for the financial support during the first period of my stay and Ghent University (BOF) for the financial support during the last six months of my Ph.D which made my dream come true. Next, I want to thank my parents my father, Bechir and my mother, Fatima, symbol of my life and all the happiness that I experienced and I still want to live. My parents are for me not merely the subject of a simple paragraph or footer text in which I pompously conclude this part of life. No, my parents allowed me to identify my star among many others, and to reach this stage safely and dignified manner. I want to let them know that if I wanted to finish my thesis it is for them and I hope I made them proud. Thanks God for providing me such parents. I also want to express my fondness for my sisters Sawssen, Anissa, Dhouha, Ikram, and my brothers Soufien and Firas. They are always there to support me, encourage me and make me see life in color through them. So thirst to live forever our love moments of complicity and sympathy. My god, bless them. I am also thankful to many friends that I met and who contributed to make Ghent a pleasant and memorable part of my life, despite of the different language and culture. TABLE OF CONTENTS Summary .................................................................................................................................. vii Samenvatting............................................................................................................................. xi List of abbreviations ................................................................................................................ xv Scope .......................................................................................................................................... 1 Chapter 1 General introduction ............................................................................................ 7 1.1 The vegetable sector in Tunisia ....................................................................................... 7 1.2 The importance of eggplant production ........................................................................... 8 1.3 Description of eggplant .................................................................................................. 11 1.3.1 Origin ................................................................................................................. 11 1.3.2 Classification...................................................................................................... 12 1.3.3 Botanical description of eggplant ...................................................................... 14 1.3.4 Physiology of flowering, fruit set and fruit ripening ......................................... 17 1.4 Salt stress: Causes and responses of plants .................................................................... 19 1.4.1 Introduction ........................................................................................................ 19 1.4.2 Causes and types of salinity ............................................................................... 21 1.4.3 Plant responses to salt stress .............................................................................. 24 1.5 Mechanisms of salinity tolerance of plants .................................................................... 29 1.5.1 Osmotic adjustment ........................................................................................... 29 1.5.2 Ion exclusion or inclusion .................................................................................. 32 1.5.3 K+/Na+ and Ca2+/Na+ ratios discrimination ....................................................... 33 Chapter 2 In vitro regeneration of eggplant........................................................................ 39 2.1 Introduction .................................................................................................................... 39 2.2 Materials and methods ................................................................................................... 41 2.2.1 Plant Material ..................................................................................................... 41 2.2.2 Effect of TDZ on callogenesis and organogenesis ............................................ 42 2.2.3 Effect of light quality on callogenesis and organogenesis ................................. 42 i 2.2.4 Statistical Analysis ............................................................................................. 42 2.3 Results ............................................................................................................................ 43 2.3.1 Effect of TDZ on callogenesis ........................................................................... 43 2.3.2 Effect of TDZ on direct organogenesis .............................................................. 45 2.3.3 Effect of light quality on callogenesis: .............................................................. 47 2.4 Discussions .................................................................................................................... 49 2.4.1 Effect of TDZ ..................................................................................................... 49 2.4.2 Effect of light quality on the weight of callogenesis and the number of shoots 49 2.5 Conclusion ..................................................................................................................... 50 Chapter 3 Effect of salt stress on germination and seedling growth in eggplant (Solanum melongena L.) .........................................................................................................................