Decreased seed shattering in Ile-1781-Leu mutant Avena sterilis ssp. ludoviciana (Durieu) Nyman with resistance to clodinafop-propargyl

Seed shattering is a central trait in the survival-related life history of plants. However, how herbicide resistance mutations affect it has not been studied. Therefore, we hypothesized that seed shattering might differ between clodinafop-propargyl-susceptible (S) and resistant (R; Ile-1781-Leu mutant) biotypes of winter wild oat. Over two growing seasons, we planted individuals from each biotype in a newly planted wheat field and, at heading stage, surrounded them with a seed trap to assess their growth, life history, and physiological traits until wheat harvest. The R biotype exhibited delayed (4-7 d), reduced (41.1%), and slowed (12.5%) seed shattering compared to the S biotype, suggesting a fitness cost. Although tillering and biomass did not differ, the R biotype showed reductions of 9.3% in height, 20.4% in seed production, and 9.4% in 1000-seed weight compared to the S biotype. The lignin content in the panicles of the two biotypes differed significantly, with the R biotype exhibiting 21.4% more lignin than the S biotype. Moreover, cellulase and polygalacturonase activities decreased by 16.9% and 19.8%, respectively, in the R biotype. The identified fitness differences may be used to develop strategies for managing this mutant in wheat fields infected to them.