DOI: 10.5061/dryad.w3r2280s3
title: Drought exposure leads to rapid acquisition and inheritance of herbicide resistance in the weed Alopecurus myosuroides

description: This dataset contains data from two-part greenhouse experiments described
 in the paper: “Vian H. Mohammad, Colin P. Osborne & Robert P.
 Freckleton (2022) Drought exposure leads to rapid acquisition and
 inheritance of herbicide resistance in the weed Alopecurus
 myosuroides”.  Globally, herbicide resistance in weeds poses a
 threat to food security. Resistance evolves rapidly through the co-option
 of a suite of physiological mechanisms that evolved to allow plants to
 survive environmental stress. Consequently, we hypothesize that stress
 tolerance and herbicide resistance are functionally linked. We address two
 questions: (i) does exposure to stress in a parental generation promote
 the evolution of resistance in the offspring? (ii) Is such evolution
 mediated through non-genetic mechanisms? We exposed individuals of a grass
 weed to drought and tested whether this resulted in herbicide resistance
 in the first generation (F1). In the first experiment (“Exposure to stress
 in a parental generation promote the evolution of resistance in the
 offspring”), the effect of three levels of drought ("none, medium and
 high") is studied in five different nive populations of
 black-grass. Plant height, above ground biomass and seed weight
 were measured to estimate the influence of drought treatments on the
 phenotype. In addition, surviving and dead plants were assessed to
 evaluate the tolerance of A. myosuroides to drought stress. The
 drought treatments were initiated 30 days after emergence. In the
 herbicide assay experiment, the seedlings of F1 of all
 populations were sprayed with fenoxaprop-P-ethyl herbicide (as “Puma
 Super” – 69 g a.i. L−1, Bayer Crop Science) using two different doses, a
 lethal dose (40 g a.i. h−1) and sub-lethal dose (20 g a.i.
 h−1). 28 days after herbicide application, dead and damaged
 plants were assessed. Surviving plants were categorised in two ways to
 account for the differential outcomes of exposure to herbicide: plants
 were categorised as ‘surviving’ if they showed no visible effects of
 herbicide exposure, or ‘damaged’ if they survived but with obvious effects
 on above ground tissues. In the second experiment ("The role
 of non-genetic inheritance"), the effect
 of two levels of drought ("none and high") is
 studied in 15 different populations of cloned black-grass plants. Each
 plant was divided into two clones. Plants were cloned to produce two
 identical seedlings for the investigation of the role of epigenetic
 mechanisms in herbicide resistance evolution. After 14 days the cloned
 plants were re-potted and allowed to establish for one week before
 initiating a drought stress treatment. One set of the
 cloned plants was exposed to drought and the second set was grown
 under well-watered conditions. Plant height, above ground biomass
 and seed weight were measured, in addition to the number of surviving and
 dead plants. The herbicide assay was carried out using the five
 populations that possessed a high rate of viability and germination rate
 in both treatments (“none” and “high” drought). At the 3-4 leaves stage in
 September 2018, the seedlings were sprayed with fenoxaprop-p-ethyl
 herbicide (“Puma Super” – 69 g a.i. L−1, Bayer Crop Science) using two
 different doses as previously described. 28 days after herbicide
 application (October 2018) dead and damaged plants were assessed as
 described above. In terms of both survival and dry mass, we find enhanced
 resistance to herbicide in the F1 plants when the parents had been exposed
 to drought. Our results suggest that exposure of weeds to drought can
 confer herbicide resistance in subsequent generations and that the
 mechanism conferring heritability of herbicide resistance may
 be non-genetic.
description: The dataset was collected during a greenhouse environment study
 at Arthur Willis Environment Centre at The University of Sheffield,
 Sheffield, England and has been analysed using R (The R Foundation for
 Statistical Computing, R version 3.6.0). For the first
 experiment, population and replicate were entered into the model, as a
 factor in two-way ANOVAs. Plant height, biomass, seed mass were
 log-transformed. In some of the data, there was uneven distribution in
 which was dealt with via log transformation of the response variable.  A
 generalized Linear Model (glm) with binomial errors were used to analyze
 the survival plants of drought treatments. To explore the effect of
 drought stress in P generation upon herbicide resistance in the F1
 generation Generalized Linear Model with a binomial error were used to
 analyze survival. For the second experiment, a linear mixed effects analysis was used to analyse the response of the cloned parental generation to drought treatment. Restricted maximum likelihood (REML) was used to estimate the parameters. To test the effects on plant height, biomass and seed production a Gaussian error distribution was assumed. Drought was entered into the model as a fixed effect. Clone ID was included as a random effect. Data on the effect of drought in cloned plants on plant height, biomass, seed mass and survivorship were analysed. Generalized Linear Mixed Models were used to analyse the effect of drought stress in parental cloned plants upon the survival of plants following herbicide application in the F1 generation. Binomial error structure was again assumed in this experiment as the dependent variable was a binomial outcome. Herbicide and drought (with an interaction term) were entered as fixed effects in the model. Blocks and clone ID were entered as random effects to produce a MS accepted for publication.
description: The readme file contains an explanation of each of the variables
 in the dataset, its measurement units. #NA =  values not available. The
 drought levels were presented in the data sheets as ("0 " =
 "none, "25" = "medium" and "75" =
 "high"). Information on how the measurements were done can be
 found in the associated manuscript referenced above.