Inheritance of resistance to tomato bacterial wilt and its implication for potato improvement in Uganda

Abstract

Bacterial wilt (Ralstonia solanacearum), known to attack over 450 plant species in the tropics and subtropics, is a devastating disease limiting tomato production in Uganda and worldwide. Two bacterial wilt resistant, two susceptible and two mildly resistant tomato cultivars were crossed in a half diallel at Kabanyolo, Uganda. Parents and F1's were root inoculated and data collected on bacterial wilt intensity at 3 day intervals 6-21 days after inoculation and analysed for bacterial wilt reactions. Combining ability results indicated that both general combining ability (G.C.A.) and specific combining ability (S.C.A.) effects were significant for bacterial wilt resistance, indicative of both additive and non-additive gene actions. However, GCA was found to be six times as large as SCA indicating the predominance of additive gene effects in bacterial wilt resistance. Cultivars MT55, MT74, MT15 and MT164 showed negative G.C.A values indicative of good sources of resistance to bacterial wilt. Hybridisation of parents (MT55, MT74, MT15 and MT164) followed by selection in segregating populations might yield inbred progeny with resistance greater than that of parents. Joint regression analysis revealed an additive-dominance model for bacterial wilt resistance with no evidence of epistasis. The results further revealed that resistance to bacterial wilt is controlled by two genes. The implication of these results to selecting for bacterial wilt 'resistance' in potato are discussed.

Key Words: Additive effects, diallel, G.C.A., S.C.A., Lycopersicon esculentum, Solanum tuberosum


(African Crop Science Journal 2001 .9(1): 9-16)