Low Temperature Delays Metabolism of Quizalofop in Resistant Winter Wheat and Three Annual Grass Weed Species

Quizalofop-resistant wheat is the core component of the recently commercialized CoAXium™ Wheat Production System. As with other herbicides, quizalofop provides better weed control at early growth stages and under optimum temperature. However, in regions with winter wheat production, quizalofop application may be affected by unpredictable, rapid temperature decreases. Temperature shifts can cause crop injury or impact weed control efficacy. In the following study, we examine the effect of reduced temperature on quizalofop content and metabolism in CoAXium™ winter wheat and three winter weed species: downy brome (Bromus tectorum L.), feral rye (Secale cereale L.), and jointed goatgrass (Aegilops cylindrica Host). Temperature conditions include either 19 or 4.5°C daytime temperatures with tissue sampling over 5 timepoints (1–16 or 18 days after treatment, DAT). Analysis features liquid chromatography coupled to tandem mass spectrometry detection of the active form of quizalofop, quizalofop acid. Quizalofop content trends reveal delayed metabolism under cooler conditions for wheat and weeds. Quizalofop content peaks within 1–2 DAT in the warmer temperatures for all species and decreases thereafter. In contrast, content peaks between 8 and 9 DAT at cooler temperatures except for downy brome. Minimal decreases in content over time generally follow cooler temperature peaks. Further, the absence of differences in maximum quizalofop content in all species suggests absorption and/or de-esterification of quizalofop proherbicide to the active form is not reduced at cooler temperatures. Final dry shoot tissue biomass does not necessarily correspond to differences in metabolism, as biomass of wheat treated with a field rate of quizalofop does not differ between temperatures. Weeds were treated with sublethal doses of quizalofop in order to monitor herbicide metabolism without causing plant death. Under this condition, weed biomass only differs for jointed goatgrass, which has a greater biomass in the cooler temperature.

Simulating Wheat Production Potential Under Near-future Climate Change in Arid Regions of Northeast Iran

Water scarcity is the key challenge in arid regions, which exacerbates under climate change (CC) and must be considered to assess the impacts of CC on cropping systems. A climate-crop modelling approach was employed by using the CSM-CERES-Wheat model in some arid regions of northeast Iran to project the effects of CC on irrigated wheat production. Current climate data for 1990-2019 and climate projections of three climate models for 2021–2050 under RCP4.5 and RCP8.5 emission scenarios were used to run the crop model. Two irrigation scenarios with different irrigation efficiencies were also simulated to investigate the impacts of water scarcity associated with changing climate and irrigation management on wheat productivity. Results indicated that mean temperature is projected to increase at the rates of 1.74–2.73 °C during the reproductive growth period of winter wheat over the study areas. The precipitation projections also indicated that the precipitation rates would decrease over most of the wheat-growing period. The length of the vegetative growth period will extend in some regions and shorten in others under the near future climate. However, the grain filling duration will reduce by about 2–4 days across all regions. The mean seasonal PET is expected to decrease by about 11 mm from 2021 to 2050 over the study areas. A mean overall reduction in winter wheat yield due to future climate conditions would be about 12.3 % across the study areas. However, an increase of 15-30% in the irrigation efficiency will be able to offset yield reductions associated with limited water supply under future climate scenarios. The results suggest that CC will exacerbate limited irrigation water availability, so implementing high-efficiency irrigation systems should be a priority to adapt to climate change in an arid cropping system.