Oxidative stress and differential antioxidant enzyme activity in glyphosate-resistant and -sensitive hairy fleabane in response to glyphosate treatment

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.摘要：本研究采用时间梯度生化测定法，评估草甘膦（glyphosate）处理对小白酒草（Conyza bonariensis）抗性与敏感生物型诱导的胁迫效应。共设置两项实验，分别考察草甘膦施用剂量与处理后的时间进程：草甘膦施用量范围为0至11840克酸当量每公顷（g ae·ha–1），测定持续至草甘膦处理后552小时（HAT）。本研究的目的为解析草甘膦处理后，抗性与敏感型毛白酒草（hairy fleabane）体内的氧化应激水平及抗氧化酶活性差异。处理后，两种供试生物型的莽草酸（shikimic-acid）积累水平在96小时前无显著差异；敏感生物型在192 HAT时全部死亡。抗性生物型体内的莽草酸与过氧化氢（hydrogen peroxide, H₂O₂）积累呈一过性，分别在288 HAT与500 HAT时与未处理植株无统计学差异。相关性分析表明，在两种生物型中，草甘膦处理后存在明确的因果关联：即莽草酸与过氧化氢积累、脂质过氧化（反映组织损伤程度）以及超氧化物歧化酶（superoxide dismutase, SOD）、过氧化氢酶（catalase, CAT）与抗坏血酸过氧化物酶（ascorbate peroxidase, APX）活性的上调。但抗性生物型的氧化应激与组织损伤程度更低，且其SOD、CAT与APX活性显著高于敏感生物型。这表明抗性生物型体内的抗氧化酶系统可能与小白酒草的草甘膦抗性机制密切相关。本研究首次报道了毛白酒草的抗氧化酶活性差异。