An amino acid substitution at position 205 of acetohydroxyacid synthase reduces fitness under optimal light in resistant populations of Solanum ptychanthum

Abstract

The Ala 205 Val substitution in acetohydroxyacid synthase confers herbicide resistance in Solanum ptychanthum, but the effect on fitness is unknown. This study aimed to compare the germination, growth, seed production and competitiveness of resistant (R) and susceptible (S) populations under various light conditions in the field and in a controlled environment. Under optimal light conditions of high irradiance and high red ⁄ far-red, the S populations produced more seeds compared with R populations, despite no difference in germination and above-ground vegetative productivity. Any reduction in light intensity and red ⁄ far-red diminished the repro-ductive ability of both R and S populations. This effect was more pronounced for S, so that, under sub-optimal conditions, there were no differences between the two types. Replacement series with three ratios of R:S (16:0, 8:8 and 0:16) showed no competitive difference between the two types. Under optimal light conditions, the S populations always had a higher reproductive output and fitness than the R populations. This would likely cause S individuals to dominate in the absence of herbicide selection pressure, if light competition is reduced.

Fitness of ALS-Inhibitors Herbicide Resistant Population of Loose Silky Bentgrass (Apera spica-venti)

“…The direction of natural selection depends on the selective pressure (e.g., herbicide) and also on the fitness of individuals facing this new pressure. In weeds, it was expected, and has also been observed, that herbicide resistant individuals had a lower fitness than their susceptible counterparts in the absence of the herbicide in terms of biomass and/or seed production ( Bergelson and Purrington, 1996 ; Purrington, 2000 ; Ashigh and Tardif, 2009 ). The presence of a fitness cost could dictate different management strategies in order to reduce the resistant population.…”

Expanding the eco‐evolutionary context of herbicide resistance research

“…Theory predicts that there will often be a cost to adaptation . However, resistance costs are not universal, and their expression has been shown to depend on the particular resistance mechanism, the specific resistance allele, the dominance of the resistance cost, pleiotropic effects on the kinetics of herbicide target proteins, genetic background and environment . The importance of fitness costs associated with herbicide resistance has been widely recognised and is evident in the wealth of studies that have endeavoured to establish costs of resistance.…”

Molecular basis of ALS- and/or ACCase-inhibitor resistance in shortawn foxtail (Alopecurus aequalis Sobol.)

“…To date, 26 amino acid substitutions at eight conserved residues in the ALS gene are known to confer ALS herbicide resistance in various weed species. These eight conserved amino acids are Ala122, Pro197, Ala205, Asp376, Arg377, Trp574, Ser653 and Gly654 (numbered on the basis of the corresponding sequence of Arabidopsis thaliana) [8][9][10][11]; in particular, the mutations at Pro 197 and Trp574 are mostly documented in field-evolved resistant weed populations [12][13][14].…”