Underground structures and mycorrhizal associations of Solanum centrale (the Australian bush tomato) Angela Dennett Faculty of Agriculture, Food and Natural Resources University of Sydney Supervisors: Prof. Lester Burgess Dr Peter McGee Dr Maarten Ryder Acknowledgements Contributions to this project have been made by so many people from across Australia they are almost too numerous to acknowledge. Funding contributions towards this project were graciously received from the Desert Knowledge CRC. Personal thanks firstly to my main supervisor, Professor Lester Burgess, for guiding me through field observations; laboratory analysis and thesis assembly; and for being so willing to help even when it has taken up his personal time. Likewise, thank you to supervisors Dr Peter McGee of Sydney University and Dr Maarten Ryder of CSIRO Sustainable Ecosystems for giving this project direction and guidance in their specific areas of expertise. The assistance of all my supervisors has not only resulted in the production of this thesis but has inspired me to begin a career as a research scientist. Thanks also to Yvonne Latham, Marie O’Hanlon and Bruce Hawke for their extensive and invaluable contributions in both field and laboratory work. Furthermore, field work in Alice Springs could not have been conducted without the resources and advice generously contributed by the staff of the Alice Springs Desert Park and Horticultural department at Charles Darwin University in Alice Springs. Special thanks to Ruth Brown, Tim Collins, Jayde Kudrenko, Wayne Tregear, and Michael “the budding horticulturist” for providing tools and digging in the dirt in less than ideal conditions. Thanks to Max Emery of Pwerte Arntarntarenhe and Neville Bonney of Wallowa (the Palmer site) for allowing sampling on their properties and offering advice and assistance. Similarly, the permission to sample on Napperby Station and at Owen Springs Detention Centre (Hatt Rd) was gratefully received. Thank you to the technical staff and students in the Agronomy, Plant Pathology and Mycorrhiza Laboratories - Jarka Geisler, Ivan Desailly, Tim Knight, Suneetha Medis and Leonie Whiffen for guiding me through the diverse glasshouse and laboratory work; and to Dr Bob Caldwell for assisting me with the phosphorus analysis. Much appreciated assistance was also provided by Anne Simpson and Emine Korkmaz of the Electron Microscopy Unit in the many attempts to obtain root sections. I am also grateful for the information provided by David Symon of the South Australian Botanical Gardens, Tony Bean of the Queensland Herbarium and Brendan Lepschi of the National Herbarium - Australia’s experts on native Solanum spp.. Finally, I am indebted to my family for their encouragement and support throughout this project. Your love and concern has been a massive help and a great example, supporting me in my faith which got me through this year. Thank you. ii Underground structures and mycorrhizal associations of Solanum centrale (the Australian bush tomato) Contents Acknowledgements…………………………………………………………………..ii Abstract………………………………………………………………………………..iv Additional keywords…………………………………………………………….iv Part 1 – Literature review………………………………………………………1 - 47 Part 2 – Research paper………………………………………………………..48 - 96 Appendix 1………………………………………………………………..97 – 102 Appendix 2…………………………………………………….supplementary disc Literature review Word count – 9294 References – 121 (69 from 1999 to 2006) Tables – 5 Figures – 10 Thesis Word count – 8355 References – 76 (38 from 1999 to 2006) Tables – 7 Figures – 17 iii Abstract Solanum centrale (Solanaceae) is an Australian indigenous food plant with potential uses as a desert crop species. This project investigated the little understood underground structures and mycorrhizal associations of S. centrale to assist the domestication process. Eight naturally colonised and cultivated sites in South and Central Australia were observed and samples of lateral and fine (secondary) roots were taken for anatomical study and to determine resprouting ability in the glasshouse. In addition, a glasshouse trial spanning 10 weeks was conducted to determine the response of S. centrale seedlings to mycorrhizal fungi and phosphorus nutrition at zero P, low P (0.15 g) or high P (0.3 g), applied as soluble phosphate. S. centrale was found to form clonal communities connected by underground lateral roots. Shoots were produced at irregular intervals on lateral roots and responded extremely rapidly and favourably to simulated disturbance in the glasshouse. Tap roots were occasionally found with a shoot and lateral roots often turned downwards to grow vertically. Fine roots were sparsely located on laterals and were old and brittle at the driest sites. Despite this, mycorrhizas were observed in the fine roots at all field sites. In the glasshouse experiment, the effect of mycorrhizal fungi on root colonisation and plant growth and development varied depending on phosphorus application. Mycorrhizal fungi colonised 48% of root length in inoculated zero P plants but only 2% of roots at low P and no roots at high P. Inoculation with mycorrhizal fungi had no effect on dry weight, root length and plant height of low or high P plants, but significantly increased growth at the zero P level (P<0.05). However inoculation increased the average root phosphorus content by 42%, decreased root to shoot ratio by 92% and decreased root biomass by 41% at all P levels, despite negligible colonisation at low or high P. This suggests that the presence of mycorrhizal fungi in the rhizosphere influences plant morphology. Furthermore, the absence of mycorrhizal associations under high P suggests that no benefit is conferred to the host in high nutrient environments. This may prevent an unnecessary drain of photosynthate from the plant when P is not limiting. The positive response of S. centrale to mycorrhizal inoculation, and its ability to rapidly resprout from roots, highlights its suitability to an arid environment. This work demonstrates the potential of S. centrale as a cultivated desert food plant. Additional keywords Aboriginal food; arid-zone flora; root-sprouting; vegetative reproduction; phosphorus response; plant hormones. iv Part 1 ‐ Literature review Solanum centrale (bush tomato) – root system adaptations to aridity and importance in the Native Food Industry Angela Dennett Faculty of Agriculture, Food and Natural Resources University of Sydney Supervisors: Prof. Lester Burgess Dr Peter McGee Dr Maarten Ryder Contents I. INTRODUCTION....................................................................................................5 II. AUSTRALIAN NATIVE FOOD PLANTS..........................................................5 (1) Introduction.........................................................................................................5 (2) Aboriginal uses ..................................................................................................6 (3) The Australian native food industry................................................................7 (a) History of the native food industry ..............................................................7 (b) The native food industry today....................................................................9 (c) Growing bushfoods .....................................................................................10 (d) Industry goals...............................................................................................11 (4) Importance of native foods ............................................................................12 (a) Indigenous community development........................................................12 (b) Sustainability and conservation ................................................................13 (c) Global food security ....................................................................................14 III. SOLANUM SPP. IN CENTRAL AUSTRALIA................................................15 (1) Taxonomy.........................................................................................................15 (2) General Description ........................................................................................15 (3) Solanum centrale ............................................................................................18 (a) Taxonomy.....................................................................................................18 (b) Distribution....................................................................................................19 (c) Description....................................................................................................21 (d) Uses ..............................................................................................................24 (e) Growth and Production...............................................................................25 IV. ROOT SYSTEMS .................................................................................................28 (1) Introduction.......................................................................................................28 (2) Anatomy and morphology of root systems in arid regions........................29 (a) Introduction...................................................................................................29 (b) Acquisition of resources .............................................................................30 (c) Reproduction and survival..........................................................................31