Impact of ALS target-site resistance mutations on Raphanus raphanistrum growth under herbicide selection

LI, M; YU, Q; VILA AIUB, MM; HAN, H; POWLES, SB

Conferencia; Global Herbicide Resistance Challenge Conference; 2013

Australian Herbicide Resistance Initiative

For herbicide resistance to evolve in plants, two conditions must be met: a resistance trait must endow a fitness advantage over the wild type under herbicide selection and this advantage should exceed any fitness or ecological disadvantage associated with the resistance trait in the absence of herbicide selection. The fitness advantage endowed by a herbicide resistance trait is conditional on the efficiency of the resistance mechanism in protecting the plants from herbicide damage. In the present study we quantified the effect of various specific homozygous target-site ALS resistance alleles (Ala-122-Tyr, Pro-197-Ser, Asp-376-Glu or Trp-574-Leu) on survival, ALS activity and growth components of Raphanus raphanistrum under chlorsulfuron (sulfonylurea) and metosulam (triazolopyrimidine) treatment. The ability of plants to respond to herbicide treatment was assessed by estimating growth traits (biomass, leaf area, relative growth rate (RGR) and components, net assimilation rate (NAR) and leaf area ratio (LAR)) when subjected to the effect of field herbicide rates. Whereas similar survival rates were observed, significant differences in growth were recorded among plants with these specific resistance alleles. Nearly no growth reduction was observed for Tyr-122 plants, while a significant growth inhibition was recorded for plants with the Glu-376. Considering all evaluated traits, it is possible to rank the ALS resistance alleles for the level of protection (fitness advantage) to both herbicides: Tyr-122 > Leu-574 > Ser-197 > Glu-376. The implication of these results for the evolution of ALS resistance in R. raphanistrum is discussed.