Factors influencing micropropagation and somatic embryogenesis of two cassava varieties, Kello and Qulle

Abstract

Abstract. Berhanu R, Feyissa T. 2020. Factors influencing micropropagation and somatic embryogenesis of two cassava varieties, Kello and Qulle. Cell Biol Dev 4: 71-81. Cassava (Manihot esculenta Crantz) is a perennial Euphorbiaceae shrub cultivated in the tropics, Africa, and Asia for its tuberous starchy roots. Lack of good-quality seed, low productivity and profit, virus and insect pests, high heterozygosity, low natural fertility, poor seed set, and seed germination limit its cultivation. The conventional breeding system is ill-equipped to address these issues. Therefore, additional biotechnological solutions are required to address the abovementioned issues. This research aimed to devise a method for obtaining a maximum number of shoots and morphologically sound in vitro materials by micropropagation, as well as to investigate the various parameters related to the micropropagation of the two cassava varieties, 'Kello' and 'Qulle.' The research also contains a somatic embryogenesis technique that is an optimal source of in vitro materials for large-scale multiplication. In this experiment, a Solid MS medium with different salt concentrations, sucrose concentrations, TDZ, a two-step procedure involving pre-soak of nodal explants in 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 utilized. At a concentration of 0.2 mg/L TDZ, both 'Kello' and 'Qulle' exhibited the highest average number of shoots per explant and improved morphological properties of in vitro material. At a TDZ concentration of 0.2 mg/L, the two-step cultivation strategy produced the greatest mean number of shoots per plant for both kinds. The maximum mean number of shoots per explant was produced by 'Kello' at a medium salt strength of a quarter, but 'Qulle' required a medium salt strength of full. 'Kello' and 'Qulle' produced the greatest average number of shoots per explant at pH values of 5.6 and 6.6, respectively. At 0.15% sucrose, 'Kello' and 'Qulle' attained their highest mean values for all parameters. During somatic embryo induction, treatments with varying doses of 2,4-D generated FEC and somatic embryos, but the somatic embryos failed to progress through the globular stage. The micropropagation property of the two types through sequential subculturing suggested that repeated subculturing causes the in vitro materials to lose their multiplication property.