Feyissa, Tileye (PhD)Jemal, Neja2018-07-092023-11-092018-07-092023-11-092009-07http://etd.aau.edu.et/handle/123456789/7245Sweet potato, (Ipomoea batatas), is vegetatively propagated crop. Due to the following cycles of propagation, viruses are accumulated, which seriously affects the sweet potato yield and quality. The objective of this work was to produce virus free sweet potato planting materials through meristem culture and chemotherapy. Stem cuttings of four cultivars were collected from Awasa Agricultural Research Center and planted in a greenhouse at Science faculty AAU. These samples were tested for the presence of sweet potato viruses using NCM-ELISA. From the infected plants, meristems were taken and cultured to make them free from viruses. In addition, shoots from all varieties were taken and treated with ribavirin under different concentrations for one month. NCM-ELISA test was carried out to confirm the success of virus elimination. The in vitro propagated plants from meristem culture were found to be virus free. Samples treated with 10 mg/l ribavirin, gave positive results for SPFMV. On the other hand, 20 mg/l and 30 mg/l, treated samples gave negative results for the tested viruses. In this study, micropropagation system in four sweet potato varieties using meristem culture was established. MS medium with 3% sucrose, 0.7% agar and different concentrations and combinations of plant growth regulators adjusted at a pH of 5.8 was used throughout all experiments. Twelve treatments for initiation of shoots from meristems were done. Significant differences in response to initiation existed among the varieties (p ≤ 0.05). Among all combinations tested, 1 mg/l BAP, 2 mg/l GA3 and 0.01 mg/l NAA gave maximum shoot initiation percentage (90% for Beletech, 70% for Koka-12 and 56.7% for Ogensegen). Shoot initiation for TIS-8250 was not possible in all of the combinations but callusing was highly evident. Shoot multiplication was dramatically improved by subculturing of the initiated shoots onto different concentrations of BAP enriched medium. The highest significant mean numbers of shoots per shooted explant (8.0 for Beletech and 6.7 for Koka-12) were obtained in 2 mg/l and 1.5 mg/l BAP containing medium respectively. Subsequently, well formed shoots were rooted on growth regulator free and IBA enriched medium. The maximum rooting percentage (100%) and the highest mean number of roots per shoot (4.2 and 3.7) were obtained from growth regulator free and 0.1 mg/l IBA containing medium for Beletech and Koka-12 respectively. Rooted plantlets were acclimatized and 91.4% of acclimatized shoots of Beletech and 73.0% of shoots of Koka-12 were survived and successfully established in the greenhouse. Key words/Phrases:-Culture initiation, Multiplication, Acclimatization, Chemotherapy, Virus testing, Sweet potatoenCulture initiationMultiplicationAcclimatizationChemotherapyVirus testingSweet potatoThesis