ALS herbicide resistance mutations in Raphanus raphanistrum: evaluation of pleiotropic effects on vegetative growth and ALS activity

Abstract

Gene mutations that endow herbicide resistance may cause pleiotropic effects on plant ecology and physiology. This paper reports on the effect of a number of known and novel target-site resistance mutations of the ALS gene (Ala-122-Tyr, Pro-197-Ser, Asp-376-Glu or Trp-574-Leu) on vegetative growth traits of the weed Raphanus raphanistrum. The results from a series of experiments have indicated that none of these ALS resistance mutations imposes negative pleiotropic effects on relative growth rate (RGR), photosynthesis and resource-competitive ability in R. raphanistrum plants. The absence of pleiotropic effects on plant growth occurs in spite of increased (Ala-122-Tyr, Pro-197-Ser, Asp-376-Glu) and decreased (Trp-574-Leu) extractable ALS activity. The absence of detrimental pleiotropic effects on plant growth associated with the ALS target-site resistance mutations reported here is a contributing factor in resistance alleles being at relatively high frequencies in ALS-herbicide-unselected R. raphanistrum populations.