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      • HARVEST
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      Genetic characterization of the acetohydroxyacid synthase (AHAS) gene responsible for imidazolinone resistance in chickpea (Cicer arietinum L.).

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      THOMPSON-THESIS.pdf (1.628Mb)
      Date
      2014-01-20
      Author
      Thompson, Courtney
      Type
      Thesis
      Degree Level
      Masters
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      Abstract
      Weed control in chickpea (Cicer arietinum L.) is challenging because of poor crop competition ability and limited herbicide options. Development of chickpea varieties with resistance to different herbicide modes of action would be desirable. Resistance to imidazolinone (IMI) herbicides in chickpea has been previously identified, but the genetic inheritance and the mechanism were unknown. In many plant species, IMI resistance is caused by point mutation(s) in the acetohydroxyacid synthase (AHAS) gene resulting in an amino acid substitution. This changes the enzyme configuration at the herbicide binding site, preventing the herbicide attachment to the molecule. The main research objective was to genetically characterize chickpea resistance to imidazolinone herbicides. Two homologous AHAS genes, namely AHAS1 and AHAS2 sharing 80% similarity were identified in the chickpea genome. A point mutation in AHAS1 at cytosine 675 thymine 675 resulting in an amino acid substitution from alanine 205 to valine 205 confers the resistance to imidazolinone in chickpea. A KASP marker targeting the point mutation was developed and effectively predicted the herbicide response in the RIL population. This same population was used in molecular mapping where the major locus for herbicide resistance was mapped to chromosome 5. Segregation analysis demonstrated that the resistance is inherited as a single gene in a semi-dominant fashion. To study the synteny of AHAS across plant species, lentil (Lens culinaris) AHAS1 was sequenced. The same mutation that confers the resistance to imidazolinone in chickpea was also found in lentil. Phylogenetic analysis indicated independent clustering of AHAS1 and AHAS2 across pulse species. In vivo and in vitro AHAS enzyme activity analysis showed inhibition of AHAS activity in the susceptible genotype CDC Frontier over time and with the increasing imidazolinone concentrations. In contrast, the resistant genotype CDC Cory did not show AHAS inhibition under the same treatments. In summary, the simple genetic inheritance and the availability of KASP marker could aid in the development of chickpea varieties with resistance to imidazolinone herbicide.
      Degree
      Master of Science (M.Sc.)
      Department
      Plant Sciences
      Program
      Plant Science
      Supervisor
      Tar’an, Bunyamin
      Committee
      Coulman, Bruce; Beattie, Aaron; Willenborg, Chris; Xiao Qiu, Xiao
      Copyright Date
      December 2013
      URI
      http://hdl.handle.net/10388/ETD-2013-12-1343
      Subject
      chickpea, imidazoline, herbicide resistance, gene mapping, marker assisted selection
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