Factors in Fluencing Micropropagation and Somatic Embryogenesis of two, Kello and Qulle, Cassava Varieties
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Date
2011-06
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Addis Ababa University
Abstract
Cassava (Manihot esculenta Crantz) is a perennial shrub of the Euphorbiaceae family grown in the tropics, African and Asian continents for its starchy tuberous roots. Its cultivation is constrained by the lack of high quality seed, low productivity and profit, virus and insect pests, high heterozygosity, low natural fertility, poor seed set and seed germination. These problems are difficult to be dealt with traditional breeding system. Therefore, other biotechnological methods are required to solve the above mentioned problems. The objective of this study was to overcome the above mentioned tribulations and come up with the best way to get a maximum number of shoots and morphologically fit in vitro materials through micropropagation and along with that to study the different factors that are associated with the micropropagation of the two cassava varieties; ‘Kello’ and ‘Qulle’. The study also includes a method of somatic embryogenesis that is an ideal source of in vitro materials for large-scale propagation. In this experiment a Solid MS medium with different salt strengths, sucrose concentrations, TDZ, a two-step procedure involving pre-soak of nodal explants into a liquid MS medium prior to culture on a solid MS medium, with different pH values, repeated subcultures and somatic embryo induction on MS medium supplemented with 2,4-D alone and in combination with 2 μM CuSO4 were used. Maximum mean number of shoots per explant as well as a better morphological property of in vitro material was obtained at 0.2 mg/L TDZ for both ‘Kello’ and ‘Qulle’. In both varieties, the two-step culture system resulted in a maximum mean number of shoots/explant at a TDZ concentration of 0.2 mg/L. A medium salt strength of quarter produced maximum mean number of shoots per explants in case of ‘Kello’ while in ‘Qulle’ at a full strength MS medium. The highest mean number of shoots per explant for ‘Kello’ and ‘Qulle’ was obtained at pH 5.6 and 6.6, respectively. For all parameters maximum mean numbers for both ‘Kello’ and ‘Qulle’ were obtained at 0.15 % sucrose. During somatic embryo induction the treatments with different 2,4-D concentrations induced FEC and somatic embryos but the somatic embryos failed to develop beyond the globular stage. The micropropagation property of the two varieties through successive subculturing indicated that repeated subculturing results in loss of multiplication property of the in vitro materials.
Key words/phrases: Manihot esculenta; Salt strength; Shoot multiplication; Sucrose; FEC; 2,4-D;TDZ
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Keywords
Manihot esculenta; Salt strength; Shoot multiplication; Sucrose; FEC; 2,4-D;TDZ