Date of Award
Bachelor of Science Honours
Faculty of Science, Technology and Engineering
Dr Ian Bennett
The utilisation of eucalypts around the world is increasing, mainly through the development of plantations. Clonal propagation has become important in some countries for production of such plantation trees. Micropropagation has been utilised to produce clones of trees selected for specific characteristics such as disease resistance, salt tolerance and fast growth rates. However, a suitable micropropagation protocol for all eucalypts has not been produced. One component of the micropropagation protocol, in which there is considerable difficulty, is the induction of adventitious roots on micropropagated shoots. Of particular interest, is the development of these procedures for Eucalyptus marginata (Jarrah) that have been selected for dieback (Phytophthora cinnamomi. Rands.) resistance. The effect of different sugar sources was examined on the rooting of jarrah shoots. Sucrose, glucose and fructose were all effective in promoting roots on jarrah in vitro. The effectiveness of each sugar varied between clones. In particular, three clones produced higher rooting on a medium containing fructose. For two of these clones the increase was as high as 30%. Interactions between auxin, sugar and ethylene were examined. Optimum root induction was obtained when approximately 10µM of auxin (indole butyric acid) and 2% sugar (sucrose or fructose) was used in the medium. As auxin and sugar concentration in the medium increased, the amount of ethylene produced also increased. Similarly, this increase in auxin, sugar and ethylene reduced the chlorophyll content of the shoots. The use of fructose appeared to produce lower amounts of ethylene than sucrose when used at the same concentration. The ethylene produced seemed to have no effect on the rooting response. The increases in rooting provided in some clones may be applicable to other clones that are difficult to root. This may lead to more efficient micropropagation with more clones being able to be produced in large numbers. This will increase the genetic diversity of clones that is currently available for jarrah breeding programs.
Fairbanks, M. M. (1996). Effect of Carbohydrate Source, Auxin and Endogenous Ethylene Upon Root Induction of Eucalyptus marginata donn EX SM. In Vitro. Retrieved from http://ro.ecu.edu.au/theses_hons/704