Grafting and 2.4-dichlorophenoxyacetic acid induced flowering in non-flowering sweetpotato in sub-tropics

Abstract

In sub-tropics, most sweetpotato genotypes do not flower at all. The aim of this study was to develop methods of inducing flowering based on the application of 2.4-dichlorophenoxyacetic acid (2.4D) and grafting of non-flowering genotypes on rootstocks of genotypes that flower. The first experiment was a 3 * 4 * 2 factorial experiment repeated in summer and winter seasons. Four levels of 2.4D (0, 40, 80 and 120 ppm) were applied at two levels (once and twice) on three sweetpotato genotypes. The second experiment involved grafting scions of two genotypes on rootstocks of flowering genotype. During summer season there were significant differences (P < 0.05) in bud and flower counts among genotypes, concentration and number of split applications but non-significant differences on all the interactions. Genotype 1 produced more buds and flowers followed by genotype 3 and 2. The highest numbers of buds and flowers were observed at 40 ppm and 80 ppm. At higher concentrations (80 and 120 ppm), the physiological disorders including leaf epinasty, shoot die back and stem cracking were extensive. The optimum concentration for 2.4D proved to be 40 ppm and could induce flowering with less physiological disorders. Split application resulted in bud death and delayed flowering. Results showed that grafting has a genotype dependent effect on flowering. Genotype 3 managed to flower but genotype 2 did not flower at all when their scions were grafted on the flowering rootstocks of genotype 1.