Combining ability and gene action for bacterial wilt disease resistance in wild tomato (Solanum pimpinellifolium) and cultivated tomato (Solanum lycopersicum) genotypes

Bacterial wilt caused by Ralstonia solanacearum is one of the most destructive and widespread diseases of tomato in Kenya. The objective of this study was to determine the combining ability effects and gene action conditioning bacterial wilt disease resistance in tomato. Eight parents were crossed in North Carolina II mating design scheme to produce sixteen F1 hybrids. The F1 hybrids and the parental genotypes were evaluated for bacterial wilt in an alpha lattice design. Among the parents, KLF acc III was the best general combiner for area under the disease progress curve (AUDPC) and disease incidence across the two cropping cycles. Red Diamond × KLF acc III, Money Maker× KK acc I, Oxyly× KLF acc III and Money Maker× KK acc II were the best specific combiners for AUDPC. Low narrow sense heritability values of 0.14, 0.16 and 0.20 were obtained for AUDPC, disease incidence and plant survival. Relative weights of additive versus non-additive gene action obtained for AUDPC, disease incidence and plant survival were 0.19, 0.20 and 0.50. General predictability ratios (GPR) values of 0.27, 0.29 and 0.50 were obtained for AUDPC, disease incidence and plant survival. These results indicated the predominance of non-additive gene action in governing the traits.