Protocol Optimization for in vitro Micro Propagation of Dioscorea bulbifera Linn. Germplasm

Abstract

Dioscorea bulbifera is a wild, underutilized yam species of nutritional and medicinal importance. It is known to treat ulcers, sores, wounds, spasms, dysentery, diabetes, and cancer and its bioactive component known as Diosgenin has exhibited anti-oxidant, anti inflammatory, antibacterial, plasmid curing, antidiabetic anticancer and anti-fertility activities. The current world demand for diosgenin is approximately between 50,000 and 80,000 kg per annum and the present world requirement of steroidal drugs for pharmaceuticals in terms of diosgenin is huge equivalent to about 10,000 tons of Dioscorea tubers per annum of which D.bulbifera provides 8-10% in addition to its highest nutritional value. In Uganda, this species inhabits forests such as Bwindi Impenetrable forest and Mabira central forest reserve among others. However, these forests are rapidly being destroyed due to deforestation. Domestication of this plant species is a viable alternative to contributing to its conservation, which can be promoted through establishing a seed system for it. Therefore, this study aimed at developing an in-vitro micropropagation protocol for Dioscorea bulbifera. Shoots were induced through culturing nodal explants on full-strength Driver and Kuniyaki Walnut (DKW) media supplemented with varying concentrations of Kinetin (Kn) (0.00, 1.50, 1.75, 2.00, and 2.25) mg/l and fixed concentrations of Benzyl aminopurine (BAP) (1.00 mg/l) and Naphthalene acetic acid (NAA) (0.50 mg/l). The shoots were rooted on half-strength DKW media supplemented with varying concentrations of Naphthalene acetic acid (NAA) (0.0, 1.5, 2.0, 2.5) mg/l. The highest number of shoots were formed on DKW medium supplemented with 1.75mg/l Kn + 1mg/l BAP + 0.5mg/l NAA at 100% compared to other shoot induction treatments. However, the hormone combination of 1.5 mg/l Kn + 1mg/l BAP + 0.5 mg/l NAA produced the tallest plantlets with the broadest leaves at mean shoot height and leaf diameter of 1.5750 cm and 1.3969 cm, respectively. On the other hand, 2.5 mg/l NAA induced the longest roots at mean root length of 6.719 cm and 100% of the shoots rooted at this hormone concentration compared to the other treatments.