GLADIOLUS SCABRIDUS - THE ROAD TO CONSERVATION AND COMMERCIALISATION By TRACEY BARBARA CAMPBELL Submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Agriculture in Horticultural Science School of Agricultural Sciences and Agribusiness Faculty of Science and Agriculture University of KwaZulu-Natal Pietermaritzburg December 2005 OECLARATION I hereby declare that the research work reported in this thesis is the result of my own investigation, except where acknowledged. Signed: -'*"'-='---;t='----"7'~\ y Barbara Campbell We certify that the above statement is correct. Signed: _~_. '_ Prof J.P. Bower Supervisor Signed: Mrs R. van Niekerk / Co-supervisor To see the world in a grain of sand And a Heaven in a wild flower, Hold infinity in the palm of your hand And eternity in an hour William Slake (1757-1827) Then God said, "Let the land produce vegetation: seed bearing plants and trees on the land that bear fruit with seed in it, according to their various kinds". And it was so. The land produced vegetation: plants bearing seed according to their kinds and trees bearing fruit with seed in it according to their kinds. And God saw that it was good. Genesis 1: 11-12 ii ACKNOWLEDGEMENTS I would like to express my sincere thanks and appreciation to the following people and organisations: Prof John Bower for his supervision, guidance and encouragement. Renate van Niekerk for her valuable comments and suggestions. The John Travis Bursary Fund and Midland's Flower Initiative for financial assistance. Or Paul Shanahan, Prof Peter Greenfield, Or Albert Modi, Ms Colleen Carlson, Or Isa Bertling and all the staff in the Plant Sciences Department for their help and advice. Special thanks to Paul Hildyard, Teri Dennison, Lowie de Klerk, Selwyn Sampson, Dave Gregory, Barry Hunkin, Quenton Tharrot, Gail Papli, Kogie Pillay, Amen Ngidi and Thomas Zuma for their cheerful and willing assistance in the ordering of chemicals, glasshouse production,lab work and sorting out any crises that occurred. Or Jeff Finnie, Prof Dick Haynes and Or Ed Granger for advice in their areas of expertise. Rob Scott-Shaw and Brigitte Church at KwaZulu-Natal Wildlife for being so willing to give of their time and for supplying plant material. My fellow postgraduates, Zelda van Rooyen, Andrew Dominy, Thabiso Lebese, Molipa Mosoeunyane (Boetie), Bob Kalala, Nicky Taylor, Vivienne Deigna-Mockey, Delia Thompson, Julius Ochuodho, Alfred Odindo, Dambuza Ngomane, Mireille Asanzi, Rendani Nemakanga, Samson Tesfay, Nathan Phiri, Rorisang Mare and Mangani Katundu, for advice, friendship, laughter and encouragement. A special thank you to Ryan Cripps for assistance with the HPLC work. Jennifer Mander at The Institute for Natural Resources, Barry Killian, the dam operator at Bivane Dam, and Impala Water User Association for making the trip to Bivane Dam possible. iii Grateful thanks and appreciation to all the garden centres and florists who so willingly gave of their time to fill in the market research questionnaire. Thanks go to the customers of 'Our Secret Garden' in Hilton who also gave of their time in this regards. Johannes Maree at Hosgro for information and advice. Mr Nevil Tyler and NET Projects for the use of computer facilities. Jonathan Tyler for his encouragement and assistance. Janet Fuller and Neil Homerfor making the trip to Bivane Dam such an adventure. Your help was greatly appreciated. Neil, you are an inspiration! lan and Usa Hobson for their support and understanding and above all for being such good friends. Thank you for giving me the opportunity to learn so much about plants! My precious family for their endless patience, love and support and for putting up with months of long, stressful working hours. My heavenly Father: 'You are my God and I will give you thanks; you are my God and I will exalt you.' Psalm 118:28. iv ABSTRACT There is at present a growing concern and awareness of the endangered status of many indigenous South African plants in the wild, a number ofwhich have potential for commercial production. One such example is Gladiolus scabridus, a vulnerable species endemic to the mountains of northern KwaZulu-Natal and southern Swaziland. It has considerable potential due to its floral characteristics. However, little is known about its horticultural requirements. Thus propagation and cultural practices were investigated with the aim of both conservation and commercialisation of the species. The ideal conditions for G. scabridus seed germination were determined. The presence or absence of light had no significant effect. Optimum germination was achieved at 20 QC of both winged and dewinged seeds. Higher temperatures appear to have a negative effect on germination and none ofthe winged seeds germinated at 30 QC. Under ideal conditions, fresh seed showed significantly higher vigour and viability than stored seed although the germination of stored seed was hampered by a higher internal fungal content. Successful tissue culture protocol was established for G. scabridus axillary bud and cormel halve explants. During the initial shoot initiation and proliferation stages (stage I and 11), the significantly higher shoot numbers occurred in the absence of growth regulators in both explant types. However, shoots with 1.0 mg 1-1 6-benzyl-amino-purine (BAP) and 0.5 mg 1-1 1-naphthalene-acetic-acid (NM) were healthier in appearance. Higher levels of 5.0 mg 1-1 NM inhibited shoot production and encouraged root development in cormel halve explants. During stage 11, axillary bud explants showed root and cormlet development. More roots were initiated without growth regulators, whilst 5.0 mg 1-1 NM resulted in significantly better cormlet development. Shoot and cormlet growth of cormel halve explants during stage II was not significantly affected by the presence or absence of NM and BAP. Significantly more roots were produced with 5.0 mg 1-1 NM. During stage III (rooting), the presence of activated charcoal (AC) was essential for the initiation and development of roots in vitro. Root and cormlet development in all explant types was significantly affected by the interaction between the previous treatments from stages I and 11 and the new treatments. During stage IV (hardening off) , most explants died down in the hardening off media leaVing resting cormlets. There was a significant interaction between 1.0 mg 1-1 NM and 0.3 % AC from stage Ill, resulting in significantly more cormlets in both axillary bud and cormel halve explants. There was successful cormletgrowth aftercold storage which is advantageous in reducing the need for acclimatization. v G. scabridus corms were successfully forced out of their normal flowering period. Temperatures of 10,5.5 and 2 QC showed successful corm initiation although the corms need to be stored for longer at warmer temperatures. It is suggested that a treatment of 2 QC for 6 weeks is the optimal condition for forcing G. scabridus corms. Although originating from a stressful environment, G. scabridus appears to show capacities for improved growth undercontrolled conditions. Fertilizer applications enhanced growth and reduced the time to flowering. Nitrogen (N) was found to be important for vegetative growth, flowering and daughter corm development, whereas potassium (K) influenced cormel production. Fertilizer with higher N and lower K is appropriate for the beginning and middle of the growing season and then adjusted to a lower N and higher K fertilizer to promote cormel formation. G. scabridus was found to produce prolific numbers of cormels which is an important source of plant material. Mineral leaf analysis showed that optimum levels for wild species are lower than those for hybrid gladioli with the optimum levels affected by physiological corm maturity and subsequent plant growth. Norms for postharvest handling of cut G. scabridus spikes have been developed. Spikes held in 2 % sucrose had a longer vase life and better floret opening and quality than those kept illl iBl in distilled water, Prolong , Chrysal , 2 % sucrose and 2 % ethanol, 1 % sucrose, 4 % sucrose, 1 % sucrose and 0.5 % Jlt<il!l, 2 % sucrose and 0.5 % JIKiBland 4 % sucrose and 0.5 iBl % JIK , 2 % fructose and 2 % glucose. The use of commercially available solutions should be used with caution. Florets produced a climacteric-like CO2 peak, but levels of ethylene were unmeasurable. Cold storage and the use ofpolypropylene sleeves delays senescence. G. scabridus spikes secrete droplets of a sticky substance which was confirmed to be extra floral nectar through HPLC analysis. Market research revealed a positive response to the species from consumers and retailers alike with potential for cultivation as a cut flower and bedding plant. However, the cost will determine supply and demand. A field study conducted at Bivane Dam, northern KwaZulu-Natal, confirmed that G. scabridus colonies prevail in rocky, quartzite outcrops where they become wedged between the rocks. Plants were found at different stages of development with populations of not more than 108 plants per colony. Soil data of G. scabridus sites was compared to that of two sites nearby. It was found that G. scabridus soils are higher in phosphorus (P), zinc (Zn) and organic carbon. Leaf analysis confirmed that they have adapted their growth to low nutrient levels. The G. scabridus studies have clearly shown that the species can be successfully moved from a wild plant to a commercially viable one and in so doing its conservation status can also be improved. vi CONTENTS