Micropropagation of Plectranthus edulis (Vatke) Agnew

Abstract

Plectranthus edulis (Vatke) Agnew belongs to the family Lamiaceae which occurs both as a wild and cultivated species. The Major constraints in the cultivation of P. edulis through the conventional propagation methods are shortage of planting materials and a long maturation period. Therefore, the objective of this study was to develop protocol of micropropagation that enables multiplication of P. edulis. Explants were sterilized using, different concentrations of NaOCl for different times of exposure. MS medium supplemented with different types and concentrations of auxin and cytokinins were used for culture initiation, shoot multiplication and root induction through nodal and shoot tip culture. Sodium hypochlorite (NaOCl) at a concentration of one percent (1 %) and exposure time of 5 minutes gave the highest percentages (74.50±0.50, 69.83±0.76) of clean culture for nodal and shoot tip, respectively. 6-(BAP) Benzylamino purine at 1.5 mg/l was found to be an optimum concentration for shoot induction, yielding 91.67±0.58 for nodal and 85.57±0.51 for shoot tip explants. The combination of 2.0 mg/l BAP with 1.0 mg/l NAA was found to be the optimum concentration yielding 10.28±0.06 and 6.12±0.01 shoots per explants for nodal and shoot tip respectively for shoot multiplication. Half strength MS medium with 2.0 mg/l IBA and 1.0 mg/l NAA gave the highest rooting percentage with optimum root number and length. Up on acclimatization and transplanting, 85 % survival efficiency was observed on soil mix ratio of 2:1:1 decomposed coffee husk, forest soil and sand respectively. There were no observable variations with respect to morphology and growth characteristics to the greenhouse raised parent plant. The results obtained in this study permit the development of mass propagation protocol that could enable large scale commercial production of P. edulis and provide a possible system towards genetic improvement of the crop using nodal as well as shoot tip explant sources.