Evaluation of effective gametocides for selective induction of male sterility in sorghum

Effective gametocides can serve as alternative agents to induce male sterility in sorghum. The objectives of this study were to evaluate the effectiveness of selected male gametocides in sorghum, to determine the optimum concentration of the chemicals and to investigate its possible effect on female sterility. Ethyl 4-fluorooxanilate (E4FO) and ethrel were evaluated on three genotypes of sorghum. The gametocides were sprayed at five concentrations at the booting stage when the panicles were released halfway from the flag leaf. Pollen and spikelet sterility were assessed using light and scanning electron microscopes. Both chemicals were effective in inducing male sterility in sorghum. However, E4FO was the more potent chemical, inducing complete male sterility with high female fertility and relatively less phytotoxicity at lower concentrations, while higher concentrations of ethrel were required to give complete male sterility. E4FO induced on average of 99.5% male sterility at 2 mg/l in all the varieties, while with ethrel 97% male sterility was obtained at 3 ml/l. Therefore we recommend to use E4FO at 2 mg/l and ethrel at 3 ml/l as male sterilizing agents to facilitate controlled crosses in sorghum.