Dr. P. R. DHARMATTISMITHA G. B.2018-11-052018-11-052015-06http://krishikosh.egranth.ac.in/handle/1/5810082904A study was conducted to assess the heterosis and combining ability for productivity and bacterial wilt resistance in tomato during 2014-15 in the Department of Horticulture, UAS, and Dharwad. The experimental material consisted of fifteen parents including ten female and five male parents. Fifty F1 hybrids were produced in a line  tester mating design for heterosis and combining ability studies. Female parents were selected with diversity for bacterial wilt and male parents with diversity for horticultural traits. Data on fruit quality characters were recorded and per cent mid-parent heterosis and better-parent heterosis were determined. The analysis of variance revealed the predominance of non-additive gene action for all the traits. The hybrids showed significant variation in heterosis. Maximum and significant heterosis in favourable direction was observed for yield, fruit number, fruits per cluster and average fruit weight. Heterosis was appreciable in all hybrids, but was more in four hybrids viz, IMP-B x DMT-2, Arka Alok x DMT-5, Arka Abha x DMT-3 and BFL x DMT-3. In respect of both gca & sca effects, the parents and hybrids differed significantly. Among the parents, IMP-B and DMT-3 were the best general combiners for yield per plant and other characters under study, and these may be used as valuable donors in the hybridization programme for producing promising combinations in bacterial wilt prone areas. Among the crosses, IMP-B x DMT-2, Arka Alok x DMT-5, Arka Abha x DMT-3 and BFL x DMT-3 were the most valuable combiners for yield per plant and also free from the bacterial wilt incidence. IMP-B x DMT-2 and Arka Abha x DMT-3 were suitable for processing. The present study reveals that heterosis breeding is useful for development of tomato through exploitation of non-additive gene action.en-USnullThesis