Abstract:
The Ethiopian lowland bamboo, (Oxytenanthera abyssinica, A. Rich), is an important plant
in both rural and urban areas of Ethiopia having myriad of uses ranging from construction,
furniture and handicrafts to food, bioenergy and medicinal values. The plant flowers once
after many decades and dies soon after flowering. The resulting genetically variable seeds
abort soon after fertilization and fail to sustain the generation due to short viability. Other
vegetative propagation methods pose difficulty in establishment as well as management and
more terribly count their ages from their mother plants and die shortly. Hence,
micropropagation from seed grown mother plants is one of the way outs to overcome this
problem. The present study was initiated at the National Plant Biotechnology Laboratory in
order to optimize in vitro protocol for mass propagation through nodal culture from one
year old bamboo plants grown in a glasshouse. The experiments were laid out in a
completely randomized design with 30 observational units per single treatment. MS basal
medium was used for all experiments. After efficacious sterilization that resulted up to
100% initiation without contamination, explants inoculated in the medium supplemented
with 2.5mgl -1 BAP resulted in 100% of initiated explants within four days. This treatment
showed other extra shoots of independent auxiliary buds sprouting from a single explant
that could incur effective signs of multiplication during initiation. For in vitro
multiplication, initiated shoots were cut in to lengths of 2 cm and treated with different
concentrations and combinations of BAP and Kinetin. In the 1st and 2nd stages of
multiplication, MS+2.5mgl -1 BAP +1.5mgl -1 kinetin resulted in higher number of shoots
per explant (5.90 and 5.84, respectively). However, MS+1.5mgl -1 BAP +1.5mgl -1 kinetin
resulted in higher number of shoots per explants in the 3rd and 4th stages. In terms of
multiple nodes per shoot, PGR free medium was the best of all the treatments. For root
induction, shoots inoculated on full strength hormone free medium developed roots (having
length of 7.3cm,>3 main roots and 36.7% rooting efficiency). Addition of wide range
concentrations of IBA (0.25-45mgl -1) resulted in drying of shoots without rooting. With the
exception of very high level of IBA concentration (50mgl -1), which showed little signs of
forced rooting, all rooting hormone treatments failed to initiate rooting. Remarkably,
straight acclimatization of the remaining percentage of shoots which failed to root in PGR
free medium and subsequent establishment by ex vitro rooting resulted in a survival rate of
43.33%, which increased the percentage of acclimatized plantlets at the same time. Hence,
in addition to the 83.3% rate of acclimatization obtained from the in vitro rooted shoots, the
overall acclimatization efficiency reached an overall survival rate of 63.3%. Therefore,
utilization of this protocol helps to generate planting materials in large scale and in short
period of time at fair cost.
