Abstract: 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.
Nomenclature: Fluazifop-P; johnsongrass, Sorghum halepense (L.) Pers. #3 SORHA; grain sorghum, Sorghum bicolor (L.) Moench ‘AKS-82’, ‘TX622’.
Additional index words: Hybridization, outcrossing, SORHA.
Abbreviations: ACCase, acetyl coenzyme-A carboxylase (EC 6.4.1.2); AOPP, aryloxyphenoxypropionate; CHD, cyclohexanedione; POST, postemergence.
