Date of Award
Master of Science (Biological Sciences)
School of Natural Sciences
Health, Engineering and Science
Ian J Bennett
Improvement of root production and ability to establish mycorrhizas from different Arbuscular Mycorrhizal Fungi (AMF) inoculum sources on two micropropagated teak (Tectona grandis L. f.) clones was examined at the acclimatisation phase. Teak shoots were maintained on a multiplication medium containing Murashige and Skoog (MS) nutrients and organics, 30 g L-1 sucrose, 0.5 μM benzyl amino purine, 0.5 μM kinetin, 2.5 g L-1 agar, 2.5 g L-1 gelrite and pH 5.8. After 35 days shoots were exposed to a rooting medium (RM) containing ¼ strength MS macronutrients, ½ strength MS iron, full strength MS micronutrients, and 20 g L-1 sucrose, 2.5 g L-1 agar, 2.5 g L-1 gelrite and pH 5.5. This RM was supplemented with indole-3-butyric acid (IBA) ranging between 0 – 160 μM to evaluate the most suitable IBA concentration for producing roots without affecting survival and growth in soil. Minimum and maximum times of exposure to IBA were also examined for periods from 4 to 28 days. Rooting in vitro, using soils made by combining sand:perlite (1:1, v/v), sand:peat (1:1, v/v), sand:peat:perlite (1:1:1, v/v/v) and agar, were also investigated as mycorrhization in vitro was pursued. Rooted teak plants were inoculated with isolated AMF spores, or inoculum product, or soil-based inoculum.
It was determined that exposure to IBA between 40 and 80 μM for 8 days, followed by transfer to RM without IBA for another 14 to 28 days, induced the most roots. Higher auxin concentrations (160 μM) did not produce more roots but decreased survival after transfer to soil. Rooting in vitro using pasteurised soils produced rooted plantlets with shorter roots than those produced on a solidified agar medium, but the plants were small and the roots did not develop so rooting ex vitro was adopted. Plants grown in inoculum comprising isolated spores showed significant differences in growth, although there were no visible features of AMF establishment. Similarly, plants grown with an unprocessed inoculum product showed hyphal development, but there were no arbuscules or vesicles evident. In contrast, 100% of the plants grown in an Australian organic farming soil treatment were colonized with AMF, and arbuscules, vesicles, spores and intra and extraradical hyphae formed. The latter plants were taller and had larger root surface areas than the other treatments after 20 weeks of acclimatisation. Surprisingly, mycorrhization was achieved despite a reasonable level of phosphorus in the soil. Variation in clone responses was also recorded. One of the clones, T201, showed a low multiplication rate and was less responsive to all treatments.
Early mycorrhization of teak plantlets might provide advantages when transferring the plantlets to the field; for example early mycorrhization might reduce transplant shock, reduce the need for inorganic fertilizers, and the extraradical mycelium could help populate the soil with AMF. Increased growth and root area found in this research cannot be solely explained by mycorrhizal establishment; it could also be a result of nutrients in the soil. Standardised rooting and mycorrhization protocols were developed for teak, but these could also be applied or adapted for other forest trees.
Ramirez Caro, M. I. (2014). Establishment of Arbuscular Mycorrhizal Fungi (AMF) on micropropagated teak (Tectona grandis L. F.). Retrieved from http://ro.ecu.edu.au/theses/1527
Available for download on Saturday, September 30, 2017