The response of glyphosate-resistant and glyphosate-susceptible biotypes of Echinochloa colona to carbon dioxide, soil moisture and glyphosate

Abstract

physiological and growth responses of two Australian Echinochloa colona biotypes (glyphosateresistant and susceptible, produced from a single population) to different concentrations of carbon dioxide (co 2) (ambient ~450 ppm and elevated ~750 ppm) and soil moisture (well-watered and waterstressed) were analyzed. Elevated CO 2 and well-watered conditions resulted in E. colona plants with greater biomass, height and numbers of tillers and leaves in both biotypes; however, no significant response was observed for seed production or the amount of photosynthesis pigments with increasing co 2 at both soil moisture levels. In addition, water availability was more influential for growth than co 2 concentration. The mean shoot biomass of the susceptible biotype under elevated CO 2 and wellwatered conditions was significantly greater than the resistant biotype. Although the susceptible biotype showed more vegetative and reproductive growth than the resistant biotype, no significant difference was observed for seed production between the biotypes in the water-stressed condition. In a second experiment, different doses of glyphosate (0, 180, 360, 720 and 1440 g a.e ha −1) were applied to both biotypes grown at two soil moisture levels (well-watered and water-stressed). In the waterstressed condition, glyphosate efficacy was decreased in both biotypes. The resistant biotype in the well-watered condition had only 19% survival at 1440 g ha −1 glyphosate (double the recommended rate), but this value increased in the water-stressed condition by 62%. Our study suggests that future climate change can affect the physiological and growth processes of weeds and their responses to herbicides. Knowledge of their adapting behaviors will be critical to weed management strategies. Climate components such as radiation, temperature and precipitation have a direct impact on the agriculture industry. Therefore, climate change could affect plant biophysiological processes and productivity 1. An increase in the emission of greenhouse gasses (carbon dioxide-CO 2 , methane-CH 4 and nitrous oxide-N 2 O 4), aerosols, temperature and evaporation, as well as a decrease in precipitation will be important factors of future climate change 2. These factors will influence other variables, such as different stresses (drought, salinity, etc), changes in pests' life cycles and soils quality 3-6. The current atmospheric CO 2 concentration, recorded at Mauna Loa Observatory, Hawaii, is 411 ppm 7. Some studies have quantified a difference of 80 ppm in the CO 2 concentration between urban and suburban areas 8,9. According to emission scenarios on climate change as reported by the Intergovernmental Panel on Climate Change (IPCC), CO 2 concentrations are predicted to be in the range between 600 to 1000 ppm at the end of the 21st century 10. Increased levels of CO 2 in C 4 weeds have less beneficial photosynthetic effects compared with C 3 weeds because they already have a pathway for inhibiting photorespiration 11. Different studies assessed that under current temp...

Efficacy of Different Herbicides on Echinochloa colona (L.) Link Control and the First Case of Its Glyphosate Resistance in Greece

“…The current study revealed that the application of the recommended label rate of glyphosate reduced dry weight of the resistant E. colona accessions (ET2 and ET4) only by 18%-22%, as compared to the untreated control. Such findings are in accordance with the corresponding of Mollaee et al [22] who noticed that the application of the recommended rate of glyphosate reduced the dry weight of a resistant E. colona by 25% under conditions of increased soil moisture, whereas this accession under water stress conditions was completely unaffected. The susceptible accession studied during this experiment was controlled by 72%, 88%, and 97% when treated with 1/2X, X and 2X rates of glyphosate.…”

“…Soil moisture conditions as well as temperature are also key factors affecting the efficacy of glyphosate against Echinochloa spp. In particular, Mollaee et al [22] noted that when treated with 1440 g a. e. ha −1 of glyphosate, the resistant population survival was recorded at 19% under increased soil moisture conditions, whereas this value was by 43% higher under water-stress conditions. Increased GR 50 values, resistance indices, and survival percentage were observed at 30 • C in glyphosate-resistant E. colona populations during both the experiments of Nguyen et al [58].…”

“…Florpyrauxifen-benzyl ester is a pyridine-2-carboxylate auxin herbicide with unique mode of action and high efficacy against broadleaves, grasses, and sedges [19]. Glyphosate is one of the most widespread and efficient non-selective herbicides globally, whose application is a common control practice for E. colona [20][21][22]. However, due to the continuous use of glyphosate, several E. colona accessions have been confirmed as resistant to glyphosate [23][24][25][26].…”

Response of glyphosate-resistant and susceptible biotypes of Echinochloa colona to low doses of glyphosate in different soil moisture conditions

“…in 2015. The glyphosate-resistant biotype was confirmed to be resistant in a screenhouse study, in which plants were sprayed with different doses of glyphosate [34]. According to an experiment conducted by Mutii et al (2019) at the Gatton research field, the glyphosate-resistant and susceptible biotypes were propagated by the cloning method that produces individual plants with the same genetic background as their parents [35].…”

“…Reduced soil moisture content resulted in a decrease in the efficacy of glyphosate [12,40]. In our previous study, we observed that in the water stressed condition, glyphosate efficacy was decreased in both biotypes [34]. This response could be caused by less absorption and translocation of glyphosate as the herbicide is mainly translocated by vascular transportation [41].…”