SUMMARY
A new route of in vitro mass propagation protocol of Gerbera jamesonii (H. Bolus ex Bolus f.) derived from application of thin cell layers (TCL) and adenine sulphate (AS) was successfully developed and established. Shoot tip explants and half-strength MS medium containing 0.25 mg/l N6-benzylaminopurine (BAP), 20 g/l sucrose and 7 g/l Swallow agar were used as explant source and basic medium. Different TCL of transversal TCL (tTCL) and longitudinal TCL (lTCL) in four slicing positions of 1, 2, 3 and 4; varieties and clones i.e. G. jamesonii ‘Black Jack’, ‘Carambole’, ‘Nuance’, ‘Violente’, 01.098 and 11.46 clone; AS concentrations viz. 0, 20, 40, 60, 80 and 100 mg/l were tested in the study. Each step of in vitro culture established had unique and specific results. In the initiation stage, first slicing position of ‘Black Jack’ shoot tip tTCL was the most optimal combination treatment to produce 7.0 shoots per explant with 13.5 leaves. The first slicing position on shoot tip explants of 01.098 clone tTCL and 20 mg/l AS in half-strength MS medium containing 0.25 mg/l BAP were the most optimal combination treatment in obtaining the highest number of shoots produced per shoot up to 9.4 shoots per shoot with 34.1 leaves and 2.37 cm length of leaves in the proliferation stage, however the treatment did not give significant effect compared to control. Under periodical subcultures on the basic medium, number of shoots and leaves increased gradually from the initial culture with 3-6 shoots per shoot and 9.4-11.6 leaves till the fourth subculture with 6-11 shoots per shoot and 16.7-28.8 leaves and declined thereafter. Subculturing of shoots in accordance to produce qualified shoots for planting materials could be carried out till sixth to seventh subculture. The highest shoot multiplication rate (SMR) was established on 01.098 clone with as high as 7.3. The well shoots were easily rooted on half-strength MS medium supplemented with 0.1 mg/l BAP, 0.05 mg/l NAA and 1.5 g/l AC. Plantlets were then transferred to ex vitro condition for acclimatization on a mixture of burned-rice husk and organic manure (1:1, v/v) with 85-100% survivability. The ‘Black Jack’ and 11.46 clone were the best genotypes on the acclimatization stage with 100% survivability of plantlets. Results of the study have implication that first slicing position of shoot tip tTCL can be applied in establishing of in vitro propagation protocol for other gerberas.