Abstract Southern crabgrass [Digitaria ciliaris (Retz.) Koeler] is an annual grass weed that commonly infests turfgrass, roadsides, wastelands, and cropping systems throughout the southeastern United States. Two biotypes of D. ciliaris (R1 and R2) with known resistance to cyclohexanediones (DIMs) and aryloxyphenoxypropionates (FOPs) previously collected from sod production fields in Georgia were compared with a separate susceptible biotype (S) collected from Alabama for the responses to pinoxaden and to explore the possible mechanisms of resistance. Increasing rates of pinoxaden (0.1 to 23.5 kg ha–1) were evaluated for control of R1, R2, and S. The resistant biotypes, R1 and R2, were resistant to pinoxaden relative to S. The S biotype was completely controlled at rates of 11.8 and 23.5 kg ha–1, resulting in no aboveground biomass at 14 d after treatment. Pinoxaden rates at which tiller length and aboveground biomass would be reduced 50% (I50) and 90% (I90) for R1, R2, and S ranged from 7.2 to 13.2 kg ha–1, 6.9 to 8.6 kg ha–1, and 0.7 to 2.1 kg ha–1, respectively, for tiller length, and 7.7 to 10.2 kg ha–1, 7.2 to 7.9 kg ha–1, and 1.6 to 2.3 kg ha–1, respectively, for aboveground biomass. Prior selection pressure from DIM and FOP herbicides could result in the evolution of D. ciliaris cross-resistance to pinoxaden herbicides. Amplification of the carboxyl-transferase domain of the plastidic ACCase by standard PCR identified a point mutation resulting in an Ile-1781-Leu amino acid substitution only for the resistant biotype, R1. Further cloning of PCR product surrounding the 1781 region yielded two distinct ACCase gene sequences, Ile-1781 and Leu-1781. The amino acid substitution, Ile-1781-Leu in both resistant biotypes (R1 and R2), however, was revealed by next-generation sequencing of RNA using Illumina platform. A point mutation in the Ile-1781 codon leading to herbicide insensitivity in the ACCase enzyme has been previously reported in other grass species. Our research confirms that the Ile-1781-Leu substitution is present in pinoxaden-resistant D. ciliaris.

中文翻译：

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Plastidic ACCase Ile-1781-Leu 存在于抗匹诺沙丁的南方马唐（Digitaria ciliaris）中

摘要 南方马唐 [Digitaria ciliaris (Retz.) Koeler] 是一种一年生杂草，通常侵染美国东南部的草坪、路边、荒地和种植系统。将先前从乔治亚州草皮生产田收集的对环己二酮 (DIM) 和芳氧基苯氧基丙酸酯 (FOP) 具有已知抗性的两种纤毛虫 (R1 和 R2) 生物型与从阿拉巴马州收集的单独的易感生物型 (S) 进行比较，以了解对吡咯烷酮的反应并探索可能的耐药机制。为了控制 R1、R2 和 S，评估了增加品诺沙登的比率（0.1 至 23.5 kg ha-1）。抗性生物型 R1 和 R2 相对于 S 对品诺沙登具有抗性。S 生物型完全控制在11.8 和 23.5 kg ha-1，导致在处理后 14 天没有地上生物量。R1、R2 和 S 的分蘖长度和地上生物量减少 50% (I50) 和 90% (I90) 的 Pinoxaden 比率范围为 7.2 至 13.2 kg ha-1、6.9 至 8.6 kg ha-1 和 0.7分蘖长度分别为 2.1 kg ha-1，地上生物量分别为 7.7 至 10.2 kg ha-1、7.2 至 7.9 kg ha-1 和 1.6 至 2.3 kg ha-1。来自 DIM 和 FOP 除草剂的先前选择压力可能导致 D. ciliaris 对 pinoxaden 除草剂的交叉抗性的演变。通过标准 PCR 扩增质体 ACCase 的羧基转移酶结构域，鉴定了一个点突变，导致 Ile-1781-Leu 氨基酸取代仅用于抗性生物型 R1。围绕 1781 区域的 PCR 产物的进一步克隆产生了两个不同的 ACCase 基因序列，Ile-1781 和 Leu-1781。然而，两种抗性生物型（R1 和 R2）中的氨基酸取代 Ile-1781-Leu 是通过使用 Illumina 平台的下一代 RNA 测序揭示的。Ile-1781 密码子中的点突变导致 ACCase 酶对除草剂不敏感，此前已在其他草种中报道过。我们的研究证实 Ile-1781-Leu 取代存​​在于抗匹诺沙登的纤毛虫​​中。