Paraquat resistance in a Lolium rigidum population is governed by one major nuclear gene.

Paraquat resistance in an annual ryegrass (Lolium rigidum Gaud.) population (AFLR1) has been attributed to reduced paraquat translocation. Genetic inheritance of paraquat resistance in this population was investigated in the present study. The paraquat dose response of progeny from 8 F(1) families was more similar to that of the resistant than the susceptible parent, while the equivalent data for a further three families were intermediate compared to those of the parental populations. No significant differences in dose response were observed between reciprocal crosses of specific F(1) families. These results suggest that paraquat resistance in AFLR1 is inherited as a dominant or partially dominant nuclear-encoded trait. Pseudo-F(2) (psi-F(2)) generation seedlings were treated with multiple dose rates sufficient to control the susceptible parental population, and observed segregation ratios in all instances conformed to a 3:1 (resistant:susceptible) segregation ratio, and this ratio was further confirmed by individual phenotyping of cloned plant genotypes. A single major nuclear gene is hence apparently responsible for evolved paraquat resistance in AFLR1.