INHERITANCE AND SELECTION EFFICIENCY OF BACTERIAL WILT RESISTANCE IN TOMATO

Bacterial wilt resistance of F-2, F-3, F-4 and F-5 generations was eva luated in tomato. Parents and each generation were transplanted into a field heavily infested with Pseudomonas solanacearum and inoculated w ith bacterial wilt. Bacterial wilt resistance was evaluated based on t he date of plant death and a resistance index from 1 (susceptibility) to 13 (high resistance) was assigned to each plant. Mean resistance in dices of the Fl generations of the 2 crosses were 4.5 and 6.2, which w ere lower than the mid-parent values of 6.9 and 7.1, respectively. The se findings suggest that bacterial wilt resistance is partially recess ive as there was incomplete dominance toward susceptibility. There was no correlation between the resistance index and fruit weight in the F -2 generations of the 2 crosses (r = -0.074, r = -0.019), indicating t hat it is possible to select plants with both high resistance and larg e fruits in segregating populations. High parent-offspring correlation between the resistance indices of the parental F-2 plants and the res istance indices of the F-3 progenies was observed and the mean resista nce indices of F-3, F-4 and F-5 progenies derived from highly resistan t F-2, F-3 and F-4 plants were higher than the mean resistance indices of the progenies derived from susceptible or moderately resistant F-2 , F-3 and F-4 plants. These findings indicate that selection of resist ance in early generations is apparently effective.