Biotechnology Department, NIDERA S.A, Ruta 8 km 376, Casilla de Correo 6, 2600, Venado Tuerto, Santa Fe, Argentina.
Theor Appl Genet. 2012 Feb;124(2):355-64. doi: 10.1007/s00122-011-1710-9. Epub 2011 Sep 30.
Ahasl1 is a multilallelic locus where all the induced and natural mutations for herbicide tolerance were described thus far in sunflower (Helianthus annuus L.). The allele Ahasl1-1 confers moderate tolerance to imidazolinone (IMI), Ahasl1-2, and Ahasl1-3 provides high levels of tolerance solely to sulfonylurea (SU) and IMI, respectively. An Argentinean wild sunflower population showing plants with high level of tolerance to either an IMI and a SU herbicide was discovered and used to develop an inbred line designated RW-B. The objectives of this work were to determine the relative level and pattern of cross-tolerance to different AHAS-inhibiting herbicides, the mode of inheritance, and the molecular basis of herbicide tolerance in this line. Slight or no symptoms observed after application of different herbicides indicated that RW-B possesses a completely new pattern of tolerance to AHAS-inhibiting herbicides in sunflower. Biomass response to increasing doses of metsulfuron or imazapyr demonstrated a higher level of tolerance in RW-B with respect to Ahasl1-1/Ahasl1-1 and Ahasl1-2/Ahasl1-2 lines. On the basis of genetic analyses and cosegregation test, it was concluded that tolerance to imazapyr in the original population is inherited as a single, partially dominant nuclear gene and that this gene is controlling the tolerance to four different AHAS-inhibiting herbicides. Pseudo-allelism test permitted us to conclude that the tolerant allele present in RW-B is an allelic variant of Ahasl1-1 and was designated as Ahasl1-4. Nucleotide and deduced amino acid sequence indicated that the Ahasl1-4 allele sequence of RW-B has a leucine codon (TTG) at position 574 (relative to the Arabidopsis thaliana AHAS sequence), whereas the enzyme from susceptible lines has a tryptophan residue (TGG) at this position. The utilization of this new allele in the framework of weed control and crop rotation is discussed.
Ahasl1 是一个多等位基因位点，迄今为止，所有关于除草剂抗性的诱导和自然突变都在向日葵（Helianthus annuus L.）中进行了描述。等位基因 Ahasl1-1 赋予对咪唑啉酮（IMI）的中等耐受性，Ahasl1-2 和 Ahasl1-3 分别仅对磺酰脲（SU）和 IMI 提供高水平的耐受性。发现并利用阿根廷野生向日葵群体培育出对 IMI 和 SU 除草剂具有高水平耐受性的自交系 RW-B。本研究的目的是确定对不同 AHAS 抑制性除草剂的交叉耐受性的相对水平和模式、遗传方式以及该系对除草剂耐受性的分子基础。在施用不同除草剂后观察到轻微或无症状表明，RW-B 对向日葵 AHAS 抑制性除草剂具有全新的耐受性模式。生物量对甲磺隆或咪草烟剂量的反应表明，RW-B 相对于 Ahasl1-1/Ahasl1-1 和 Ahasl1-2/Ahasl1-2 系具有更高的耐受性。基于遗传分析和共分离测试，结论是原始种群对咪草烟的耐受性是由一个单一的、部分显性核基因遗传的，该基因控制着对四种不同的 AHAS 抑制性除草剂的耐受性。拟等位基因测试使我们能够得出结论，RW-B 中存在的耐受等位基因是 Ahasl1-1 的等位变体，并将其命名为 Ahasl1-4。核苷酸和推导的氨基酸序列表明，RW-B 的 Ahasl1-4 等位基因序列在第 574 位（相对于拟南芥 AHAS 序列）具有亮氨酸密码子（TTG），而敏感系的酶在该位置具有色氨酸残基（TGG）。讨论了在杂草控制和轮作框架中利用这个新等位基因的问题。
