Abstract

Most sweet potato cultivars grown in Zimbabwe are poor in agronomic and quality traits and require improvement through breeding. However, most cultivars rarely flower yet the flowers are crucial in genetic improvements. The aim of this study was to determine the effects of different levels of 2, 4-dichlorophenoxyacetic acid (2,4-D) on sweet potato flower induction. A 3*4 factorial experiment in a randomized complete block design with three replications was used. The first factor was landrace with three different landraces and the second factor was 2,4-D with four different concentrations (0, 100, 300 and 500 ppm). The 2,4-D was applied 50 days after planting. Sweet potato landraces that were sprayed with 2,4-D showed morphological and physiological disorders that included temporal drooping, petiole epinasty, stem splitting, shoot dieback and root swelling. Extensive morphological and physiological disorders were observed on landraces that were sprayed with the high levels of 2,4-D (300 and 500 ppm). However, within 30 days, all the landraces that were sprayed with 2,4-D managed to initiate buds and set flowers while the plants that were not sprayed did not flower at all. The Friedman’s tests showed no significant differences in bud and flower number among the treatment combinations used. Therefore the lowest concentration of 2,4-D (100 ppm) used in this study is probably close to the optimum concentration for flower induction in sweet potato. Although this concentration is not the actual optimum, at the moment this concentration can be used to induce flowering in sweet potato and thus allow sweet potato breeding initiatives to be launched.

Key words: Sweet potato, 2, 4-dichlorophenoxyacetic acid, flowering, seed set.