Micro-Propagation of Disease Resistant Cassava Variety in Rwanda

Abstract

Cassava (Manihot esculenta) belongs to the Euphorbiaceae family and has about 100 species. In Rwanda, it plays a key role as food security and income generating crop. It is described as “classic food security crop” because it offers the advantage of a harvest even in situations of erratic rainfall and infertile soils. Cassava is a major staple food in Rwanda but production has been drastically declining in the last decade due mainly to diseases, pests and lack of disease resistant varieties. Among the major diseases, viral diseases are the most important in tropical Africa and Cassava Brown Streak Disease (CBSD) is the most damaging, causing over 50% yield loss and threatening the livelihoods of farmers. Recently, the Rwanda Agriculture Board (RAB) acquired some elite cassava varieties that are resistant to Cassava Mosaic Disease (CMD) and CBSD. The objective of this study was to develop an efficient, rapid tissue culture protocol for propagating the elite varieties. Nodal explants harvested from in vitro–grown plantlets were cultured on different Murashige and Skoog (MS) formulations. In a separate trial, full, half and one-quarter MS media were supplemented with 5, 10, 20 and 40 μM/l Giberellic acid (GA₃). The Tukey test showed that there were highly (p=0.0027) significant differences among the different GA₃ levels for shoot elongation in cassava. The best regeneration media was full MS media supplemented with 40 μM/l GA₃ that gave the highest mean shoot length of 8.93 ± 2.67 mm. Plantlets were successfully transferred to sterile soil mixture (soil: sand: manure in the ratio of 3:2:1) and acclimatized in the greenhouse. The new protocol developed in this research will enhance rapid production of high quality cassava planting materials for increased food security in Rwanda.

Keywords: Cassava, Manihot esculenta, tissue culture, microshoot regeneration

Rwanda Journal, Volume 24 Series E 2011