Inheritance of resistance to 2,4-D and chlorsulfuron in a multiple-resistant population of Sisymbrium orientale

BACKGROUNDA population of Sisymbrium orientale from South Australia has multiple resistance to auxinic herbicides and inhibitors of acetohydroxyacid synthase (AHAS). Inheritance of resistance to 2,4-D and chlorsulfuron was studied in this population. RESULTSCrosses were made between seven resistant individuals as pollen donors to seven susceptible individuals. Sixteen F-1 individuals from three crosses were identified by their lack of strong epinasty when treated with 200 g 2,4-D ha(-1). These individuals were selfed, and segregation analysis of strong epinasty in the resulting progeny fitted a 3:1 ratio for resistant:susceptible individuals when treated with 200 g 2,4-D ha(-1), as predicted by a single major gene. A detailed dose-response analysis of the F-2 populations to 2,4-D confirmed single-gene inheritance. Analysis of segregation to 1 g chlorsulfuron ha(-1), a concentration that kills all susceptible individuals, was unable to determine the mode of inheritance. A detailed dose-response analysis indicated that two genes contributed to chlorsulfuron resistance: a dominant target-site mutation of Pro 197 to Ser and a second gene with dose-dependent dominance. CONCLUSIONSThis population has a single dominant allele conferring 2,4-D resistance, whereas two genes contribute to chlorsulfuron resistance. Single dominant gene inheritance demonstrates that 2,4-D resistance can be readily selected. (c) 2014 Society of Chemical Industry