Efficacy of the chemical trifluoromethanesulfonamide as a male gametocide in field-grown sorghum [Sorghum bicolor (L.) Moench]

Sorghum bicolor (L. Moench) is a cereal grain and forage crop that is grown across tropical and temperate regions of the world. Sorghum has a complete flower, resulting in self-pollination as the primary form of reproduction, but it is also grown commercially as a hybrid. Consequently, methods of cross-pollination for both breeding and hybrid seed production are important. In sorghum breeding, current methods of cross-pollination are effective, but they have limitations in terms of achieving complete and temporal male sterility. With the development of new breeding approaches, such as doubled haploids, temporal male sterility is essential. Temporal male sterility would also be useful in testing new seed parent lines prior to an investment in sterilization of the line in the cytoplasmic male sterility system. The objective of this study was to evaluate the efficacy of trifluoromethanesulfonamide (TFMSA) as a sorghum male gametocide under field conditions. TFMSA was foliarly applied to three male-fertile parental lines, in two environments, using a pipette and a sprayer, respectively, in dosages ranging from 5 to 30 mg/plant. Repeated applications over time for the 10 and 15 mg dosage rates were conducted on a subset of individual plants. The results indicate that once a minimum dosage threshold (between 10 and 15 mg) was reached, panicles became male sterile. Additional dosages and number of applications had little overall effect, and both hand-applied and sprayer-applied TFMSA had similar male sterility induction capability. From these studies, it appears that TFMSA can be used as an effective chemical male gametocide on sorghum under field conditions.