Abstract

Strategies to manage bacterial wilt disease causing 64-100% yield loss have limited effectiveness. A 10×10 diallel mating design excluding reciprocals and self was employed in this study to evaluate combing ability effects, heterosis, and reaction to bacterial wilt in 10 tomato parents. Genotypes AVTO1424 (11.87%), AVTO1429 (12.29%) and AVTO1314 (13.53%) were found to have significantly lower disease incidence, demonstrating high levels of bacterial wilt resistance. Commercial varieties Roma VF (89.87%) and Cal J (79.60%) however had the highest disease incidence. Out of 45 F1 hybrids, 10 had an incidence <20% and severity score <1, while 12 F1 hybrids had an incidence >75% and severity score >4. The cross AVTO1429 x AVTO1314 had the lowest incidence (7%). Negative heterosis was recorded in 29 and 31% of the F1 hybrids during long and short rain respectively, with AVTO1429 x AVTO131 having the lowest at -50 and -37%. Cal J had the highest General Combing Ability while AVTO1314, AVTO1429 and AVTO1424 had the lowest. Cross UC82 x Valoria select and AVTO1429 x AVTO1424 had the highest Specific Combining Ability while cross Danny select x Riogrande had the lowest. Genotypes with bacterial wilt resistance trait and high combining ability have the potential in developing a breeding program.

Key words: Bacterial wilt, combining ability, heterosis, Ralstonia solanacearum, tomato

Abbreviation

AEZ: Agro-ecological zones; AVRDC: World Vegetable Centre; Cfu: colony forming unit; CV: Coefficient of variation; g: grams; ha: Hectares; l: litres; LSD: Least significant differences of means at (P≤0.05); m: meters; ml: millilitre; t: tonnes.