Inheritance of glyphosate resistance in Echinochloa colona from Australia

Glyphosate resistant Echinochloa colona is widespread in fallow systems of northern Australia from intensive glyphosate use. The inheritance of glyphosate resistance and the potential for gene transfer through pollen from resistant to susceptible individuals were investigated. A glyphosate resistant population A533.1, containing a mutation in EPSPS, was used as the resistant parent and Echi S as the susceptible parent. Gene flow via pollen between adjacent susceptible and resistant individuals was examined by treating progeny from the susceptible individuals at 240 g ha-1 glyphosate with 1.38% gene flow detected. Survivors were selfed and the progeny segregated 3:1 for survival to 240 g ha-1 glyphosate, consistent with single dominant gene inheritance. Hand crosses between resistant and susceptible individuals produced a single F1 seed which carried the mutation in EPSPS. The F2 generation from the hand cross had a response to glyphosate, intermediate between the two parents and similar to that expected for a single largely dominant gene. Sequencing the EPSPS cDNA detected at least two EPSPS genes expressed in E. colona, only one of which carried the mutation. Glyphosate resistance in this population of E. colona is inherited as a single largely dominant allele.