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

BACKGROUND A 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. RESULTS Crosses 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. CONCLUSIONS This 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. © 2014 Society of Chemical Industry