Weak and strong target site ALS resistance mutations in Raphanus raphanistrum: correlation between resistance at the ALS and plant level

GARCÍA, FEDERICO; GIL, MERCEDES; NESTARES, GRACIELA; GUNDEL, PEDRO. E.; VILA AIUB, MM

Congreso; Resistance'19 Rothamsted; 2019

Despite thelargely known effect of target site ALS resistance mutations in endowing plantsurvival under treatment of ALS inhibiting herbicides in many weeds, it remainsunknown whether plants with these resistance mutations can reproduce similarlyto an environment without ALS treatment.  The resistancelevel of Raphanus raphanistrum (wildradish) with either the homozygous Ala-122-Tyr or Asp-376-Glu resistancemutations growing under chlorsulfuron treatment in a wheat crop was evaluated. The resistance level was estimated at both the plantand enzyme (ALS activity) scales.  Results showed a similar level of survival in plantsexhibiting either of the mutations and a positive correlation between ALSactivity and fecundity under chlorsulfuron treatment. Plants with theAla-122-Tyr mutation showed higher ALS activity and siliques mass than plantswith the Asp-376-Glu mutation. Plants with the Ala-122-Tyr mutation showed noreduction in the mass of siliques produced under chlorsulfuron herbicide andwheat competition compared to the control treatment (no chlorsulfuron, nowheat). However, plants with the Asp-376-Glu mutation significantly reduced thereproductive output under herbicide and wheat competition compared to anenvironment with no herbicide and crop.  The observed results enable to rank these ALSmutations in wild radish as ecologically strong (Ala-122-Tyr) and weak(Asp-376-Glu).