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Articles by J.N. Oggema
Total Records ( 2 ) for J.N. Oggema
  J.N. Oggema , M.G. Kinyua and J.P. Ouma
  Embryogeneic callus induction and subsequent differentiation is accomplished by application of suitable growth regulators and controlling conditions during culture. The growth regulator, 2,4-D is one of the most effective auxin for calli induction in sweet potato (Ipomoea batatas (L.) Lam.), however the optimum concentration varies with individual cultivars. The optimum 2,4-D level for the local sweet potato cultivars has not been determined yet it is important in multiplication of planting material and transformation procedures. To determine the optimum 2,4-D concentration that produced embryogenic calli early and in high frequencies for local Kenyan sweet potato cultivars Mugande, SPK004, Kemb10, Japon tresmesino and Zapallo, leaf explants were cultured in vitro on MS basal medium supplemented with six concentrations of 2,4-D (0, 0.5, 1.0, 2.0, 3.0 and 5.0 mg L-1), set as a factorial treatment arranged in a Completely Randomized Design (CRD), replicated three times. For each treatment four parameters were considered: Mean number of days taken to form calli, calli weight, calli diameter and calli strength. The results established significant (p<0.05) differences in cultivar responses to 2,4-D levels. Calli induction was effective when supplemented at low levels of 0.5 mg L-1 as high levels above 3.0 significantly reduced the quantity and quality of embryogenic calli that was formed. Low levels of 2,4-D should be used for local Kenyan sweet potato cultivars as the number of days taken to form calli reduced and calli incidences increased.
  J.N. Oggema , J.P. Ouma and M.G. Kinyua
  The development of a reliable plant regeneration protocol in sweet potato forms the basis for sweet potato (I. batatas) genetic improvement. The success in production of the transgenic sweet potato is dependent on the reliability and efficiency of the regeneration protocol to produce somatic embryos capable of forming whole plants. The effect of direct and indirect embryogenesis on in vitro plant regeneration was studied and thereafter a suitable tissue culture protocol for 5 locally adapted Kenyan sweet potato cultivars Mugande, SPK004, Kemb10, Japon tresmesino and Zapallo established. Embryogenic calli was induced directly and indirectly from sweet potato leaf explants and auxiliary buds cultured on MS medium supplemented with 2,4-D (0, 0.5 and 1.0 mg L-1). Absisic acid was added to induce embryo maturation and when the hormone levels were reduced these embryos began to differentiate into shoots before whole plants were regenerated. For each treatment the number and days taken to form shoots, roots and plants that were regenerated were counted and used as a selection index of an efficient sweet potato regeneration protocol for the locally adaptable Kenyan cultivars. The test cultivar had a significant (p≤0.05) effect on both direct and indirect embryogenesis. The use of indirect embryogenesis was beneficial for the local Kenyan sweet potato cultivars as more calli formed hence ensuring higher plant regeneration and increased mass propagation of in vitro plants while direct embryogenesis took a shorter time to form shoots and roots but fewer plants were regenerated.
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