Reduced translocation in 2,4-D-resistant oriental mustard populations (Sisymbrium orientale L.) from Australia

BACKGROUNDTwo oriental mustard populations (P2 and P13) collected from Port Broughton, South Australia were identified as resistant to 2,4-D. The level of resistance, mechanism and the mode of inheritance for 2,4-D resistance in these populations were investigated. RESULTSPopulations P2 and P13 were confirmed to be resistant to 2,4-D at the field rate (600g a.e. ha(-1)). P2 and P13 were 81- and 67-fold more resistant than the susceptible populations (S1 and S2) at the dose required for 50% mortality (LD50), respectively. No predicted amino acid modification was detected in sequences of potential target-site genes (ABP, TIR1 and AFB5). Resistant populations had reduced 2,4-D translocation compared with the susceptible populations, with 77% of [C-14]2,4-D retained in the treated leaf versus 32% at 72h after treatment. Resistance to 2,4-D is encoded on the nuclear genome and is dominant, as the response to 2,4-D of all F-2 individuals were similar to the resistant biotypes. The segregation of F-2 phenotypes fitted a 3: 1 (R: S) inheritance model. CONCLUSIONResistance to 2,4-D in oriental mustard is likely due to reduced translocation of 2,4-D out of the treated leaf. Inheritance of 2,4-D resistance is conferred by a single gene with a high level of dominance. (c) 2017 Society of Chemical Industry