Measuring variability in phytotoxicity testing using crop and wild plant species

Abstract

Abstract-A series of experiments was conducted to assess the level of variability in phytotoxicity testing and to investigate factors that may explain some of the observed uncertainties and inconsistencies. The work was conducted in greenhouse or growth chamber environments with plants growing individually in pots and harvested 28 d after spraying with two herbicides, glyphosate and atrazine, as formulated products. Between six and 10 doses were used on five or six replicates, necessitating over 4,500 individually growing plants.In the first set of experiments, several ecotypes (originating from different areas of the world) of eight wild plant species were tested. Significant differences in sensitivity to atrazine and glyphosate were found among ecotypes of most species tested. In the second suite of experiments, the reproducibility of results during different seasons (when growing conditions vary) was investigated using three crops and four wild plant species. Results showed that seasonal variability elicited a pronounced discrepancy in response between plants tested at different times of the year. It was found that no consistent effects could be attributed to the biotic or abiotic factors investigated. Several ecotypes of the same species differed in their seed size, percentage germination, or germination requirements, as well as in growth patterns, but these differences could not explain differences in herbicide sensitivity. Likewise, differences in phytotoxicity could not be attributed to factors such as temperature, light intensity, and sunlight duration. The present study supports the inclusion of an uncertainty factor in risk assessments to account for the intrinsic variability in plant sensitivity to herbicides. Environ. Toxicol. Chem.

Sublethal effects of the herbicide glufosinate ammonium on crops and wild plants: short-term effects compared to vegetative recovery and plant reproduction

“…Therefore, if conservation of wild species is the primary intention, then ecologically relevant test species should be favoured in phytotoxicity testing, alongside the agronomically significant species for non-target crop protection. Furthermore, this experiment, and other research (Boutin et al 2004;White et al 2009;Boutin et al 2010) have demonstrated that wild species are easily workable into phytotoxicity testing protocols.…”

“…The reluctance to use wild species as indicators has often been attributed to difficulties in germination and cultivation. Crops are often chosen because they are considered fast growing and predictable; however, recent work has found that many wild species can be easily utilized in phytotoxicity evaluations White et al 2009;Boutin et al 2010). Comparisons of crop and wild species in terms of sensitivities to herbicides have produced mixed results.…”

Comparing effects of low levels of herbicides on greenhouse‐ and field‐grown potatoes (Solanum tuberosumL.), soybeans (Glycine maxL.), and peas (Pisum sativumL.)

“…Not only can the current population be affected, but the following generation may have reduced germination and emergence, as has been shown previously for older plants treated with glufosinate ammonium [5]. Considerable variability also exists within ecotypes of native plants and within cultivars of crops having greater than a single order of magnitude of difference in their EC25 values [27,28]. The variation changes with plant species and herbicide [27,28].…”

“…Considerable variability also exists within ecotypes of native plants and within cultivars of crops having greater than a single order of magnitude of difference in their EC25 values [27,28]. The variation changes with plant species and herbicide [27,28].…”

A comparison of the herbicide tolerances of rare and common plants in an agricultural landscape

“…Dose–response patterns may also be different for exposures at different growth stages or for different response measures, such as seed production . Also, genetic variability will play a critical role in determining plant response to a given herbicide , and intraspecific variation among populations experiencing different environments and selections pressures is likely to be as important in determining herbicide tolerances as variation among species. We obtained seeds for our experiments from plant nurseries in Minnesota and Pennsylvania from plant lines that were raised under more controlled conditions.…”