In vitro Plant Regeneration of Cyphomandra betacea through Nodal Culture

Abstract

Cyphomandra betacea (Cav.) is commonly known as tamarillo or tree tomato. This species is mainly used for its edible fruits which have a high nutritional value and contain relatively high amounts of vitamins B6, C, E and provitamin A. The cultivation of tamarillo in Rwanda is facing major challenges caused mainly by viral diseases like tamarillo mosaic virus (TaMV). These pathogens are difficult to control and are transferred by vegetative propagation, often resulting in heavy productivity losses and poor quality fruits. The conventional methods of propagating Tamarillo are both slow and inefficient. This study was conducted to develop an efficient, rapid propagation protocol for C. betacea through in vitro nodal culture. The effect of phytohormones on bud break and subsequent microshoot proliferation from nodal explants was evaluated. The nodal explants were cultured on Murashige and Skoog media supplemented with different concentrations of Benzyl amino purine (BAP), 2- isopentenyl adenine (2iP) and kinetin as well as 100 mg/l myo-inositol 3% sucrose and gelled with 0.3% gelrite. The Tukey test showed that there were highly (p=0.001) significant differences among the different cytokinin levels for microshoot elongation in tamarillo. Although, microshoots developed in all the media evaluated, BAP at 40 μM/l was the most effective in inducing bud break and multiple shoots. This media induced multiple shoots at an average rate of 1.42±0.34 shoots per node and the highest shoot length of 39.25±9.05mm after 35 days in culture. The microshoots were able to root without addition of an exogenous auxin and the plantlets successfully hardened in the greenhouse. The study has developed a very simple one step regeneration protocol which can be adopted to mass propagate Tamarillo. This reproducible protocol opens new prospects for massive propagation of tamarillo and will go a long way in alleviating the shortage of tamarillo disease-free planting materials in Rwanda.

Keywords: Tissue culture, Cyphomandra betacea, Tamarillo, microshoot

Rwanda Journal, Volume 24 Series E 2011