Factors affecting micropropagation and acclimatization of an elite clone of Eucalyptus tereticornis Sm.

Several factors influencing micropropagation of a selected elite clone of Eucalyptus tereticornis Sm. were investigated. Amongst different cytokinins tested, 6-benzyleadenine proved to be the most effective cytokinin for shoot multiplication and elongation. The initial size of the shoot clump (inoculum) also influenced shoot multiplication and elongation. The number of shoots proliferated per culture vessel were significantly higher (342 shoots per culture vessel) when larger shoot clumps (15-20 shoots) were inoculated, compared to smaller shoot clumps (4-5 shoots), which resulted in a reduced shoot proliferation rates (245 shoots per culture vessel). However, the number of elongated shoots (65 per culture vessel) and shoot length (5.23 cm) were higher in cultures which were inoculated with smaller shoot clumps in comparison to those cultures which were inoculated with larger shoot clumps (54 shoots per culture vessel with shoot length of 4.17 cm). The maximum number of rooted shoots (80.7 %) was obtained on one fourth-strength MS medium supplemented with 5.0 mu M indolebutyric acid. The number of shoots proliferated, elongated, rooting frequency, and subsequent survival of plants after acclimatization were higher in cultures incubated under photosynthetically active radiation (PAR) compared to those incubated under cool fluorescent lights (CFL). Osmotic potential of the sap and chlorophyll content of cultures incubated under PAR were also higher than those incubated under CFL. Following transfer of plants to soil, inoculation with a suspension of Bacillus subtilis (plant growth-promoting bacterium) increased the survival rate of plants by 10 %, yielding successful transfer of 84 % of plants. Random amplified polymorphic DNA and inter simple sequence repeat analyses indicated a high level of clonal uniformity amongst regenerated plants and also with that of the mother plant.