Enhanced rates of herbicide metabolism in low herbicide-dose selected resistant Lolium rigidum.
Enhanced rates of herbicide metabolism in low herbicide-dose selected resistant Lolium rigidum.
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DOI：
10.1111/pce.12017
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发表时间：
2013-04
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影响因子：
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通讯作者：
Q. Yu;Heping Han;Greg Cawthray;Shaofang Wang;S. Powles
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文献类型：
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作者：
Q. Yu;Heping Han;Greg Cawthray;Shaofang Wang;S. Powles
黑麦草是一种专性异花授粉、遗传多样性的物种，也是一种经济上重要的易产生除草剂抗性的杂草。我们之前的工作表明，对具有低除草剂使用率的最初易感的刚性乳杆菌种群进行反复选择会导致快速的除草剂抗性进化。在这里，我们报告了刚性乳杆菌低剂量选择的二氯草灵耐药性的机制。结果表明，抗性并非由于靶位点 ACCase 突变或过量生产，或除草剂叶片吸收和易位差异所致。甲基敌草灵体内去酯化为植物毒性的敌草灵酸的过程非常迅速，并且在耐药人群和易感人群中相似。然而，抗性植物中二氯草酸进一步代谢为无毒代谢物的速度总是比易感植物更快，导致抗性植物中二氯草酸的水平降低高达 2.6 倍。这与抗性植物中双氯草酸代谢物的水平高出两倍非常吻合。从色谱上看，二氯草酸的主要极性代谢物与天然耐受物种小麦的代谢物相似。显然，以降低的除草剂用量进行反复选择是为了提高非靶标位点的除草剂代谢率，可能涉及细胞色素 P450 单加氧酶。
Lolium rigidum is an obligately cross-pollinated, genetically diverse species and an economically important herbicide resistance-prone weed. Our previous work has demonstrated that recurrent selection of initially susceptible L. rigidum populations with low herbicide rates results in rapid herbicide resistance evolution. Here we report on the mechanisms endowing low-dose-selected diclofop-methyl resistance in L. rigidum. Results showed that resistance was not due to target-site ACCase mutations or overproduction, or differential herbicide leaf uptake and translocation. The in vivo de-esterification of diclofop-methyl into phytotoxic diclofop acid was rapid and similar in resistant versus susceptible populations. However, further metabolism of diclofop acid into non-toxic metabolites was always faster in resistant plants than susceptible plants, resulting in up to 2.6-fold lower level of diclofop acid in resistant plants. This corresponded well with up to twofold higher level of diclofop acid metabolites in resistant plants. The major polar metabolites of diclofop acid chromatographically resembled those of wheat, a naturally tolerant species. Clearly, recurrent selection at reduced herbicide rates selected for non-target-site-based enhanced rates of herbicide metabolism, likely involving cytochrome P450 monooxygenases.