Dissertation (MSc Biodiversity)Three experiments were conducted at AVRDC-ESA, Arusha-Tanzania in 2014/2015, to assess performance of Tanzanian commercialtomato cultivars “Tanya”, “Tengeru 2010”, and “Tengeru 97” grafted on the tomato rootsock lines(“BF OKITSU 101”, “HAWAII 7996” and “R3034-3-10-N-UG”) with specific objectives: (1) to determine survival rate of the grafted seedlings; (2) to evaluate the effect of grafting on vegetative growth(days to 50 % flowering (ND50FL),fruit maturity (ND50FMT), plant height at 50 % flowering (PH50FL) and at fruit maturity (PH50FMT)); and (3) to evaluate effect of grafting on tomato fruit yield. Twelve treatments, comprising nine rootstock-scion grafting combinations and three un-grafted scions were evaluated using RCBD. Statistical analyses were computed into means using CoStatversion 6.204 (CoHort Software, CA, USA). ANOVA was employed to determine treatment effects. Results revealed variations in survival, “Tengeru 2010” and “Tengeru 97” grafted on “HAWAII 7996” demonstrating the highest survival (85 %), “Tanya” grafted on “R3034-3-4-10-N-UG” had the least survival (68 %). “Tanya” grafted on “BF OKITSU 101” exhibited delayed flowering. “Tengeru 97” grafted on „BF OKITSU 101‟ and „HAWAII 7996‟ demonstrated earliness in flowering (6 days), “Tengeru 2010” and “Tengeru 97” grafted on “R3034-3-4-10-N-UG” delayed flowering of up to 10 to 13 days. “Tanya” grafted on “R3034-3-4-10-N-UG” reduced plant heights. Grafting affected plant height mainly in the field conditions (P<0.05) compared to screen house (P>0.05). Results on fruit yield in many cases “Tanya” grafted on different root stocks reduced fruits while “Tengeru 97” increased fruits compared to mother plants. It could be concluded that more experiments to be performed in the absence of pest Tuta absoluta to confirm these findings.