Development of Biotechnological Tools for the Genetic Improvement of Selected Elite Clones of Eucalyptus Tereticornis Sm.

Abstract

Eucalypt is the most important plantation hardwoods in the world (Turnbull, 1991), yielding industrial wood, fuel wood, essential oils and important raw material for pulp and paper industry. In this study micropropagation for selected clones of Eucalyptus tereticornis was developed using nodal explants. Murashige and Skoog (MS, 1962) medium was used throughout the experimentation. It was supplemented with varying concentrations of BA and NAA. Cultures were established using nodal segments taken from freshly coppiced shoots and about 50% of nodal explants sprouted on medium supplemented with BA (2.5 µM) and NAA (0.5 µM). Shoot multiplication was found to be better on MS medium supplemented with 2.5 µM BA and 0.5 µM NAA in both the clones namely Y8 and T1. Incorporation of a steroid compound (referred to as ‘Compound A’ : earlier not known for its activity on plant tissues) into the basal MS medium showed beneficial effect on shoot proliferation as well as rooting in clone Y8 at concentration of 0.25 mg/l. In medium supplemented with BA (2.5 µM) and NAA (0.5µM) ‘Compound A’ was found to be beneficial for shoot proliferation only. Leaves segments taken from in vitro grown shoots were used as explants to establish the regeneration protocol. The explants were inoculated on modified MS medium supplemented with different concentrations of BA and 2,4-D. Shoots regeneration was observed on MS medium supplemented with 5.0 µM BA and 1.0 µM 2,4-D in both the clones. For rooting, 1-2 cm long shoots were cultured on root induction medium containing different concentrations of NAA, IBA and IAA (1 µM, 2.5 µM, 5.0 µM and 10.0 µM). Maximum rooting was obtained on medium supplemented with NAA followed by IBA and IAA. Plantlets were then successfully transferred to green house conditions with a survival rate of 70%. Attempts were made to develop a protocol for genetic transformation of Eucalyptus tereticornis clone Y8 using Agrobacterium tumefaciens and Particle gun bombardment. Callus was obtained from Agrobacterium infected as well as particle gun bombarded tissues on selection medium. Further efforts are being made to achieve regeneration from these calli.