Salinity Tolerance of Giant Swamp Taro (Cyrtosperma merkusii); In vitro and In vivo By Shiwangni RAO A thesis submitted in fulfilment of the requirements of the Degree of Master of Science School of Biological and Chemical Sciences Faculty of Science, Technology and Environment The University Of the South Pacific September, 2011 ©Shiwangni Rao 2011 0 Author Declaration I Shiwangni Rao, declare that this thesis is my own work and that, to the best of my knowledge, it contains no material substantially overlapping with material submitted for the award on any other degree at any institution, except where due acknowledgement is made in the text. i Supervisor Declaration This is to declare that this thesis titled “Salinity Tolerance of Giant Swamp Taro Cyrtosperma merkusii” submitted in fulfilment for the Degree of Master of Science in Environmental Science to the University of the South Pacific, is the original research work of Miss Shiwangni Rao conducted under our supervision and guidance. It contains no material that is overlapping with material submitted for the award on any other degree at any institution, except where due acknowledgment is made in the text. Principle Chief Supervisor; Dr. Anjeela Jokhan Dean Faculty of Science Technology and Environment University of the South Pacific P.O. Box 1168 Suva Principle Co-supervisors: Dr. Mary Taylor Genetic Resources Coordinator/Centre of Pacific Crops and Trees (CePaCT) Secretariat of the Pacific Community Private Mail Bag Suva Signature: Date: ____02/12/11_________ ii Dr. Arthur Webb Division of Science and Technology Secretariat of the Pacific Community Private Mail Bag Suva Signature: iii Acknowledgement I would like to acknowledge the very important people that have helped me throughout this research. First and foremost the Australian Government, who provided the funding for this research through the International Climate Change Adaptation Initiative (ICCAI). Dr. Anjeela Jokhan the chief principle supervisor for introducing me to the sponsors of this research. For being the academic guiding light throughout the research in terms of building the research and write-up. Dr. Mary Taylor the co-supervisor, for accepting me as a candidate for this research and allowing me to conduct my research at the Centre for Pacific Crops and Tress (CePaCT), Narere. For giving her full support despite her busy schedules and encouraging my exposure in the field of scientific research. Also for introducing me to the resource personnel’s and for her continuous academic and technical support. Dr. Arthur Webb co-supervisor, for his scientific and technical input and advice during the research, especial for the ground water salinity survey in Tuvalu. The staff of CePaCT, for teaching me tissue culture and for their moral and technical support during the experimental phase of the research. University of the South Pacific Research committee for considering this research as significant and the developments that can be achieved through it and giving their approval. The technical staff in the chemistry and biology departments namely Rosely Sharm, Shelvin Singh, Dinesh Sharma and Roselyn Lata. The Tuvalu Agriculture Minister Mr. Itai Lausaveve for guiding my stay in Tuvalu and for his technical support. The Kaupule members and agriculture officers of Nanumaga, Nanumea, Niutao, Nui and Nukulaelae for providing me with iv information and technical support. The very enlightening farmers of the six surveyed islands of Tuvalu for sharing their knowledge on the giant swamp taro. The Federated States of Micronesia, Pohnpei State Department Chief Agriculture officer Mr. Adelino Lorens, the office staff and the agriculture field technicians at the pilot farm. For all their technical support in the two day workshop in Pohnpei, helping in translation, collection of information in the farm. The farmers that participated in the workshop for sharing their bulk of knowledge and contributing in the development of the Giant swamp taro Cyrtosperma merkusii Descriptor List. I would also like to acknowledge my husband Mr. James Chand, for his continuously encouragement and pushing me to go the extra mile in my research. For being understanding, for his prayers and advice during the research. My Parents Mr Mahendra Prakash, Mrs. Shanti Mani and my sisters for their moral support and prayers. Finally, I would like to thank the many people that have not been listed above but have in their very own little way contributed to the smooth running and the successfully completion of this research project Thank you all. v Abstract Climate change related sea level rise together with adjustments to wind and wave patterns may cause an increase in the incidence of salt water intrusion into fresh ground water lenses, particularly in atoll islands. This saline intrusion may end up in Giant swamp taro (Cyrtosperma merkusii) cultivation pits, a crop which is a major food on these atoll islands and also a great part of their cultural identity. Hence, an increase in the salinity levels of the fresh ground water not only threatens the food security of these atoll island communities, but also their identity. In past literature, Giant swamp taro has been referred to as slightly salt tolerant. It has been seen to survive at a salinity level of around 2-3ppt (Dunn, 1976; Manner, 2006: Webb, 2007). However, these salinity levels are only claims and have not been tested in controlled trials. Therefore, there is an urgent need to investigate the salt tolerance potential of Giant swamp taro and utilize it as a buffer against increases in ground water salinity. Furthermore, the documentation along with sustainable conservation of giant swamp taro is also essential to prevent the loss of traditional knowledge and diversity of this important crop. Given that climate change is expected to increase the incidence of salt intrusion into giant swamp taro pits, the fundamental endeavours of this project were threefold (a) to investigate the incidence of salt water intrusion in Tuvalu (b) to develop the knowledge base of giant swamp taro through a descriptor list (c) to develop a rapid in vitro screening methodology for salt tolerance screening which could be used to assess the salinity tolerance of two groups of swamp taro cultivars, Ikaraoi and Katutu from Kiribati. A preliminary in vivo method for screening for salt tolerance was also developed. The ground water salinity survey in Tuvalu was carried out over a period of five weeks and six islands were visited. Measurements were taken using a salinity meter. The survey showed ground water salinity levels between 2006 and 2010 increased on Funafuti but not on the other islands. An in vitro method was developed for rapid screening. Using this methodology, the two cultivar groups from Kiribati were shown to survive salinity concentrations of VI 0% (0ppt), 0.5% (5ppt), 1.0% (10ppt), 1.5% (15 ppt) and 2% (20ppt) salt. However, the in vivo plants were only able to tolerate up to 0.5% (5pp) salt concentrations, possibly due to stress imposed by other environmental factors. However, further research is needed for both the ground water salinity survey and the salt tolerance screening. Further investigations would give both a clearer idea of the incidence of increase in ground water salinity levels and also the variation that might exist in salinity tolerance with different cultivars. A more clear understanding of the extent to which genetic diversity can affect salt tolerance would assist the selection of hardier cultivars. There is much significant scientific value to be gained from this project, as limited studies have been carried out generally on giant swamp taro and determining the level of salinity tolerance is essential so that farmers and communities know which cultivars they can use as they try to manage climate change. VII Contents Author Declaration ..................................................................................................... i Supervisor Declaration .............................................................................................. ii Acknowledgement ..................................................................................................... iv Abstract .................................................................................................................... VI 1.0 INTRODUCTION ................................................................................................ 1 2.0 LITERATURE REVIEW .................................................................................... 5 2.1 ATOLL GROUND WATER LENS ................................................................... 5 2.1.1 Threats to fresh ground water lens ............................................................... 7 2.2 SALINITY TOLERANCE IN PLANTS ........................................................... 9 2.2.1 Effects of increased soil salinity ................................................................ 11 2.2.2 Plant Response ........................................................................................... 13 2.2.3 Approaches to salt tolerance ...................................................................... 17 2.2.4 Salinity Testing .......................................................................................... 21 2.3 GIANT SWAMP TARO (Cyrtosperma merkusii) ........................................... 24 2.3.1 Origin ......................................................................................................... 27 2.3.2 Current Distribution