Low herbicide doses can change the responses of weeds to subsequent treatments in the next generation: metamitron exposed PSII‐target‐site resistant Chenopodium album as a case study

Abstract

BACKGROUNDIt is well known that exposure to mild stress can precondition organisms to better tolerate subsequent stress exposure in the same or future generations. Since herbicide hormesis also represents a moderate stress to exposed plants, a transgenerational priming is likely but not proven. Especially in herbicide‐resistant weeds showing enhanced reproductive fitness after regular herbicide treatments, the ability to induce resilient offspring phenotypes via hormesis may hasten the evolution of herbicide resistance in weeds. This hypothesis was studied for the triazinone metamitron in an F1 offspring generation of PSII target‐site resistant (TSR) plants of Chenopodium album propagated after parental conditioning with various metamitron doses.RESULTSIn two independent dose–response greenhouse trials, there was a positive correlation between the strength of the stimulatory response during parental preconditioning and the magnitude of transgenerational changes in herbicide sensitivity and hormesis expression. Parental conditioning at subhormetic and toxic concentrations lead to less resilient offspring, while conditioning doses that induced a pronounced hormetic effect in F0 plants had a sensitivity‐reducing and hormesis‐promoting effect on the offspring. The observed reduction in sensitivity in F1 plants compared to unconditioned F1 plants was up to 2.2‐fold.CONCLUSIONSThis study demonstrates that hormetic herbicide treatments have the ability to prime weeds for enhanced tolerance to subsequent treatments in the next generation. Effects proved dose sensitive and may act in concert with other stimulatory adaptations in plant populations. This is relevant for weed control and herbicide resistance evolution, but also for herbicide side‐effects that go beyond the exposed area. © 2020 The Author. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Glyphosate hormesis mitigates the effect of water deficit in safflower (Carthamus tinctorius L.)

“…ha −1 ). The maximum stimulus found by Belz 16 in Chenopodium album plants treated with low doses of metamitron was 120% to 149% of control, and this gradually increased with the increase in hormetic dose, increasing vegetative growth. In another study, Silva et al 7 .…”

“…39,40 The ⊍ parameter (Equation 4) was predefined as 0.25, 0.5 or 1. Model settings with different ⊍ values were compared and the one with the lowest residual sum was chosen to achieve significance in parameter f. 16,41 When both models (Equations 3 and 4) produced f > 0 for the same data set, Akaike information criterion (AIC), Bayesian information criterion (BIC) and mean square error (MSE) were used as selection criteria, and the model with lower values of these was chosen. The significance of hormesis was validated by the likelihood ratio test using the F-test (⊍ = 0.05), testing the difference in the residual sum of squares of the models (RS Eqn (2) − RS Eqn (3) or Eqn (4) ), this difference is associated with inclusion of parameter f. This is equivalent to testing the hypotheses: H 0 , there is no hormetic effect (f = 0) versus H a , there is a hormetic effect (f ≠ 0).…”

“…The α parameter (Equation ) was predefined as 0.25, 0.5 or 1. Model settings with different α values were compared and the one with the lowest residual sum was chosen to achieve significance in parameter f 16,41 …”

“…[5][6][7][8][9][10][11][12][13][14] In this context, the term hormesis refers to an adaptive/protective response caused by chemical stressors when used in low doses in plants. 15 The most widely used herbicide in the world, glyphosate, causes hormesis, 1,3,9,16,17 and studies are ongoing to elucidate the ability of low doses of glyphosate to stimulate plant growth 13 and improve agricultural sustainability by reducing environmental impacts. 18 Research into doses that cause a stimulatory effect allow us to understand the mechanisms of hormesis by glyphosate in plants and crop behavior in the field.…”

Getting ready for the ozone battle: Vertically transmitted fungal endophytes have transgenerational positive effects in plants

“…It has been shown to occur in response to herbicides and particularly in the presence of ozone (Agathokleous et al, 2019a,b, 2020b). Amazingly, it could be expressed in the progeny through a specific factor‐mediated TGE (Belz, 2020). Although our study was not designed to analyse this, we did see a positive stimulus of maternal ozone on progeny plant survival under certain conditions, by the symbiotic association with endophyte fungi.…”