Protocol Optimization for In Vitro Propagation of the Ethiopian Lowland Bamboo (Oxytenanthera abyssinica, A. Rich) through Nodal Culture

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.