Fluazifop-P Resistance Expressed as a Dominant Trait in Sorghum (Sorghum bicolor)

Reports of resistance to grass-selective herbicides, including johnsongrass (Sorghum halepense) resistant to fluazifop-P, have become quite common. Experiments were conducted to determine if fluazifop-P resistance could be transferred from johnsongrass to crop sorghum (Sorghum bicolor) and to identify the heritability of resistance in the progeny. A population of male sterile, fluazifop-P-sensitive sorghum, AKS-82, was interplanted with fluazifop-P-resistant johnsongrass and progeny treated with 0.105 kg ai/ha fluazifop-P postemergence (POST). Surviving seedlings were backcrossed to fluazifop-P-resistant johnsongrass. Viable plants from this successful cross were then testcrossed to another sensitive sorghum, TX622. These testcross progeny were then screened for herbicide resistance by again applying fluazifop-P POST at 0.105 kg/ha. Chi-square analysis revealed that resistance to fluazifop-P was inherited by a single, dominant gene. Natural hybridization of johnsongrass and sorghum is possible, and transfer of herbicide resistance between species can occur.