播娘蒿对双氟磺草胺的抗性水平及靶标抗性分子机理

为明确麦田杂草播娘蒿对双氟磺草胺的抗性水平及靶标抗性分子机理，采用整株-剂量响应法测定了播娘蒿对双氟磺草胺的抗性水平，通过克隆测序进行了靶标乙酰乳酸合成酶(ALS)基因序列比对分析，并通过测定靶标酶离体活性，分析了抗性和敏感种群播娘蒿ALS对双氟磺草胺的敏感性。结果显示，与敏感种群TS 相比，抗性种群G₁₃₀ 对双氟磺草胺产生了高水平抗性，抗药性指数为108.6；在G₁₃₀种群中随机抽取100株，对其ALS基因进行测序，比对分析发现，33%植株ALS 的第197位脯氨酸突变为苏氨酸，40%植株ALS 的第574位色氨酸突变为亮氨酸，27%植株的ALS 同时存在上述两种突变。ALS 离体活性测定结果表明，双氟磺草胺对抗性种群ALS 的活性抑制中浓度为敏感种群的137.8倍。这说明，播娘蒿抗性种群ALS 关键位点氨基酸的突变可能是导致其对双氟磺草胺产生高水平抗性的重要原因之一。

Resistance to Florasulam in Descurainia sophia L. and Its Molecular Resistance Mechanism

Experiments were conducted to investigate the resistance level of a potential resistant(R) Descurainia sophia(L.) population G₁₃₀ to florasulam. To identify its molecular resistance mechanism,acetolactate synthase(ALS) gene fragments were amplified,sequenced and compared with that of susceptible(S) population(TS); in vitro ALS assays were also conducted to compare the differences of ALS sensitivity between R and S D.sophia populations. The results showed that the R population G₁₃₀ had high-level resistance to florasulam,with resistance index(RI) of 108.6 compared with S population TS. ALS sequence analysis showed that 33% of R plants tested exhibited a Pro-197-Thr mutation; 40% of R plants tested exhibited a Trp-574-Leu mutation,and 27% of R plants tested exhibited both of the above mutations in single plant. In vitro ALS assays revealed that the concentration of florasulam required to inhibit 50% ALS activity(I₅₀) for G₁₃₀ was 137.8-fold greater than that required to inhibit the S population. This study demonstrated that the mutations in the ALS gene was one of main reasons for the resistance to florasulam in resistant D.sophia population G₁₃₀.