Abstract
ABSTRACT Biochemical assays in a time-course were employed to evaluate stresses induced by glyphosate treatment in resistant and sensitive biotypes of Conyza bonariensis. Two experiments were conducted assessing glyphosate doses and time-course after treatment. The doses of glyphosate ranged from 0 to 11840 g ae·ha–1 and assessments performed until 552 h after glyphosate treatment (HAT). The objectives of this study were to evaluate the oxidative stress and differential antioxidant enzyme activity in glyphosate-resistant and -sensitive biotypes of hairy fleabane after glyphosate treatment. After treatment, both studied biotypes accumulated similar levels of shikimic-acid until 96 h. The sensitive biotype died at192 HAT. Shikimic-acid and hydrogen peroxide (H2O2) accumulation in glyphosate-resistant biotype were transient and did not differ from untreated plants at 288 and 500 HAT, respectively. In both glyphosate-resistant and -sensitive biotypes, a correlation analysis established a cause-and-effect relationship after glyphosate treatment, which leads to shikimic-acid and hydrogen peroxide accumulation, lipid peroxidation (indicates tissue damage) and an enhancement in the activity of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) enzyme. However, in the glyphosate-resistant biotype, the oxidative stress and tissue damage were lower, and antioxidant enzyme activities SOD, CAT, and APX were higher than in the -sensitive biotype. It indicates that antioxidant enzyme in glyphosate-resistant biotype might be related to the glyphosate-resistance process in Conyza bonariensis. This study is the first report of differential antioxidant enzyme activity in hairy fleabane.
Highlights
Hairy fleabane (Conyza bonariensis (L.) Cronq.), belonging to the botanical Asteraceae family, is native to the Americas and has a cosmopolitan distribution (Shrestha et al 2014; Bajwa et al 2016)
Segregation experiments performed in the first (F0) and second (F1) self-pollinating generations evaluated at 28 days after treatment (DAT) presented results of 100% of alive in B11R and 100% of death in B17S
The data were fitted to the non-linear log-logistic model, and after that used to estimate resistance factor (RF) (Fig. 1; Table 5)
Summary
Hairy fleabane (Conyza bonariensis (L.) Cronq.), belonging to the botanical Asteraceae family, is native to the Americas and has a cosmopolitan distribution (Shrestha et al 2014; Bajwa et al 2016). Hairy fleabane is highly competitive on crops and is among the most challenging weed species to management around the world (Shrestha et al 2014; Bajwa et al 2016; Concenço and Concenço 2016). The intensive use of glyphosate has been a factor in weeds evolving resistance, rendering glyphosate treatment ineffective (Baucom and Holt 2009) in at least 42 weed species (Heap 2018). (horseweed) was the first broadleaf weed to evolve glyphosate-resistance (GR), which was observed in the United States in 2000 (VanGessel 2001). The GR in C. bonariensis was first documented in 2005 in Brazil (Vargas et al 2007)
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