Inheritance and Selection Efficiency of Bacterial Wilt Resistance in Tomato

Bacterial wilt resistance of F2, F3, F4 and F5 generations was evaluated in tomato. Parents and each generation were transplanted into a field heavily infested with Pseudomonas solanacearum and inoculated with bacterial wilt. Bacterial wilt resistance was evaluated based on the date of plant death and a resistance index from 1 (susceptibility) to 13 (high resistance) was assigned to each plant. Mean resistance indices of the F1 generations of the 2 crosses were 4.5 and 6.2, which were lower than the mid-parent values of 6.9 and 7.1, respectively. These findings suggest that bacterial wilt resistance is partially recessive as there was incomplete dominance toward susceptibility. There was no correlation between the resistance index and fruit weight in the F2 generations of the 2 crosses (r = -0.074, r = -0.019), indicating that it is possible to select plants with both high resistance and large fruits in segregating populations. High parent-offspring correlation between the resistance indices of the parental F2 plants and the resistance indices of the F3 progenies was observed and the mean resistance indices of F3, F4 and F5 progenies derived from highly resistant F2, F3 and F4 plants were higher than the mean resistance indices of the progenies derived from susceptible or moderately resistant F2, F3 and F4 plants. These findings indicate that selection of resistance in early generations is apparently effective. Discipline: Plant breeding/Horticulture Additional key words: breeding, Lycopersicon esculentum, fruit weight, correlation, Pseudomonas solanacearum JARQ 31, 195-204 (1997)