Abstract
Global climate change, specifically rising temperature, can alter the molecular physiology of weedy plants. These changes affect herbicide efficacy and weed management. This research aimed to investigate the combined effect of heat stress (HS) and sublethal doses of herbicides (four active ingredients) on adaptive gene expression and efficacy of herbicide on Echinochloa colona (L.) Link (junglerice). Three factors were evaluated; factor A was E. colona generation (G0-original population from susceptible standard; G1 and G2 were progenies of recurrent selection), factor B was herbicide treatment (florpyrauxifen-benzyl, glufosinate-ammonium, imazethapyr, quinclorac and nontreated check) and factor C was HS (30 and 45 °C). The herbicides were applied at 0.125× the recommended dose. Recurrent exposure to HS, combined with sublethal doses of herbicides, favors the selection of plants less susceptible to the herbicide. Upregulation of defense (antioxidant) genes (APX: Ascorbate peroxidase), herbicide detoxification genes (CYP450 family: Cytochrome P450), stress acclimation genes (HSP: Heat shock protein, TPP: Trehalose phosphate phosphatase and TPS: Trehalose phosphate synthase) and genes related to herbicide conjugation (UGT: UDP Glucosyltransferase) was significant. The positive regulation of these genes may promote increased tolerance of E. colona to these herbicides.
Highlights
Accelerated world population growth means intensifying demand for food, both in quantity and quality [1]
Dose response assays were performed to determine the level of sensitivity after the herbicide-susceptible Echinochloa colona parental population was treated with sublethal doses of florpyrauxifen-benzyl, glufosinate-ammonium, imazethapyr or quinclorac under optimal or high temperature, over three consecutive cycles
The combination of quinclorac plus high temperature leads to an upregulation of HSP genes; lower transcript accumulation was detected compared to optimal temperature. These results indicate that heat shock proteins are most likely to play a role in mitigating the effect of quinclorac
Summary
Accelerated world population growth means intensifying demand for food, both in quantity and quality [1]. Echinochloa (mainly, E. colona, E. crus-galli and E. phyllopogon) includes the most troublesome weeds in rice [7,8]. E. colona can cause between 1.5% and 100% yield losses in rice mainly due its rapid. Herbicides are still the most important tools for weed management because of their cost-effectiveness, rapid action, ease of use and residual efficacy in the case of soil-active compounds [12]. The intensive and extensive use of herbicides exerts high selection pressure on weed populations, selecting rare individuals with the ability to survive or escape the herbicide treatment, leading to a gradual loss of herbicide efficacy [12,13]
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