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首页> 外文学位 >Resistance to ALS-inhibiting herbicides in common ragweed, foxtail and horseweed.
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Resistance to ALS-inhibiting herbicides in common ragweed, foxtail and horseweed.

机译：对普通豚草，狐尾和马草中的ALS抑制性除草剂具有抗性。

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摘要

Acetolactate synthase (ALS) is a key enzyme in the biosynthesis of the branched-chain amino acids valine, leucine, and isoleucine. Five commercialized classes of ALS-inhibiting herbicides, sulfonylureas (SUs), imidazolinones (IMIs), triazolopyrimidines (TPs), pyrimidinylthiobenzoates (PTBs), and sulfonylaminocarbonyltriazolinones (SCTs) are known to inhibit ALS. However, weed resistance to ALS inhibitors evolved quickly, with the first resistant prickly lettuce observed only 5 years after the first use of SU herbicides. The overall objective of this study was to gain insights into the molecular mechanisms of resistance to ALS inhibitors in common ragweed (Ambrosia artemisiifolia), foxtail (Setaria spp.) and horseweed (Conyza canadensis ).;In most cases, resistance to ALS-inhibiting herbicides is due to an altered target site with reduced sensitivity to the herbicides. ALS enzyme activity assay results confirmed that resistance in several biotypes used in this study were target-site based and biotypes had different cross-resistance patterns among ALS-inhibitor classes at the enzyme level. Since different groups of herbicides have slightly different binding sites on the acetolactate synthase molecule, these results indicated that these biotypes possessed different mechanisms of ALS-inhibitor resistance.;Amino acid substitutions that confer resistance to ALS inhibitors in weeds have been reported at six different sites (Ala122, Pro 197, Ala205, Asp376, Tryp574 and Ser 653), and each site is located within a highly conserved region of the ALS enzyme. Based on PCR amplification of specific alleles (PASA) and herbicide efficacy data, it was concluded that tryptophan to leucine substitution at position 574 was the predominant basis for resistance to cloransulam in common ragweed. However, this mutation could not fully account for resistance in several populations, which displayed resistance to imazamox but not to cloransulam. Entire ALS gene sequence data indicated that valine to alanine substitution at position 205 was also a resistance-conferring mutation in common ragweed populations.;Polyploidy among foxtail species complicated the study of ALS inhibitor resistance because the number of ALS genes varied with the level of ploidy. Chromosome counting and flow cytometry were used to detect the ploidy level for each species. The results indicated that green foxtail was diploid (2X=18) whereas giant and yellow foxtail were tetraploid (4X=36). Consistent with this, Southern blot analysis revealed that green foxtail had one copy of ALS, and both giant and yellow foxtail had two copies of ALS. Substitution at position 653 was associated with IMI resistance in green and yellow foxtail. Both W574L and S653N substitutions were identified in giant foxtail.;The entire coding sequence of the ALS gene from horseweed was amplified and sequenced from sensitive and resistant horseweed biotypes using polymerase chain reaction primers created from Helianthus annuus and Xanthium strumarium ALS gene sequences. The amino acid sequences were deduced and compared to identify amino acid polymorphisms conferring ALS inhibitor resistance. Substitutions at amino acid positions 197 and 376 were identified.;Based on the results and mechanisms identified from the above three weeds, PCR-based molecular markers have been used in this study to investigate the evolution of cloransulam resistance in common ragweed, which appeared in the same year as cloransulam was commercialized. The results revealed that resistance to cloransulam in common ragweed evolved in response to selection by ALS inhibitors other than cloransulam. Also, resistance-conferring ALS alleles were used to develop a marker to assess the genotype of horseweed at codons encoding amino acid position 197. In this way we have found an effective approach to confirm the hybridization of horseweed biotypes by applying a PCR-based molecular marker. This marker is being used in ongoing studies to investigate the inheritance of glyphosate resistance in horseweed.
机译：乙酰乳酸合酶（ALS）是支链氨基酸缬氨酸，亮氨酸和异亮氨酸生物合成中的关键酶。已知有五种商业化的ALS抑制性除草剂，磺酰脲类（SUs），咪唑啉酮类（IMI），三唑并嘧啶类（TPs），嘧啶基硫代苯甲酸酯类（PTB）和磺酰基氨基羰基三唑啉酮类（SCT）。但是，杂草对ALS抑制剂的抗性迅速发展，在首次使用SU除草剂后仅5年观察到了第一种抗性多刺莴苣。这项研究的总体目标是深入了解普通豚草（Ambrosia artemisiifolia），狐尾（Setaria spp。）和马草（Conyza canadensis）对ALS抑制剂的抗性分子机制；在大多数情况下，对ALS抑制的抗性除草剂是由于靶位改变，对除草剂的敏感性降低。 ALS酶活性测定结果证实，本研究中使用的几种生物型的抗性是基于靶位点的，并且在酶水平上，ALS抑制剂类之间的生物型具有不同的交叉抗性模式。由于不同种类的除草剂在乙酰乳酸合酶分子上的结合位点略有不同，因此这些结果表明这些生物型具有不同的ALS抑制剂抗性机制。在六个不同的位置报道了对杂草赋予ALS抑制剂抗性的氨基酸取代（Ala122，Pro 197，Ala205，Asp376，Tryp574和Ser 653），并且每个位点都位于ALS酶的高度保守区域内。根据特定等位基因（PASA）的PCR扩增和除草剂功效数据，可以得出结论，在豚草中，色氨酸对亮氨酸的取代是574位对氯氰舒兰抗性的主要基础。但是，这种突变不能完全解释几个人群的抗药性，这些人群显示出对咪唑莫司的抗药性，但对氯兰舒兰没有抗药性。整个ALS基因序列数据表明，在普通豚草种群中205位的缬氨酸取代丙氨酸也是赋予抗药性的突变。;狐尾物种中的多倍性使ALS抑制剂抗性的研究变得复杂，因为ALS基因的数量随倍性水平的变化而变化。使用染色体计数和流式细胞仪检测每种物种的倍性水平。结果表明，绿色的狐尾是二倍体（2X = 18），而巨大的和黄色的狐尾是四倍体（4X = 36）。与此相符的是，Southern印迹分析显示绿色的狐尾有一个ALS拷贝，而巨大的和黄色的狐尾都有两个ALS拷贝。 653位的取代与绿色和黄色狐尾的IMI抗性相关。 W574L和S653N取代均在巨大的狐尾中鉴定出;使用从向日葵和Xanthium strumarium ALS基因序列创建的聚合酶链反应引物，从敏感和抗性马草生物型中扩增和编码了来自马草的ALS基因的完整编码序列。推导并比较氨基酸序列以鉴定赋予ALS抑制剂抗性的氨基酸多态性。鉴定了197和376位氨基酸的取代基。基于以上三种杂草的鉴定结果和机理，本研究基于PCR的分子标记研究了豚草对氯兰舒兰抗药性的演变。克兰舒兰同年商业化。结果表明，普通豚草对氯兰舒兰的抗药性是由于除氯兰舒兰以外的ALS抑制剂的选择而产生的。此外，赋予抗性的ALS等位基因被用于开发标记，以评估编码氨基酸位置197的密码子上的马草基因型。通过这种方式，我们发现了一种有效的方法，可以通过应用基于PCR的分子来确认马草生物型的杂交标记。该标记物正在进行的研究中，以研究马草中草甘膦抗性的遗传。

著录项

  • 作者

    Zheng, Danman.;

  • 作者单位

    University of Illinois at Urbana-Champaign.;

  • 授予单位 University of Illinois at Urbana-Champaign.;
  • 学科 Biology Plant Physiology.
  • 学位 Ph.D.
  • 年度 2007
  • 页码 100 p.
  • 总页数 100
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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