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      • HARVEST
      • Electronic Theses and Dissertations
      • Graduate Theses and Dissertations
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      Influence of Genome-Specific Granule-Bound Starch Synthase I (GBSSI/Waxy) on Starch Composition, Structure and In Vitro Enzymatic Hydrolysis in Wheat (Triticum aestivum L.)

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      AHUJA-DISSERTATION.pdf (6.189Mb)
      Date
      2015-10-23
      Author
      Ahuja, Geetika
      Type
      Thesis
      Degree Level
      Doctoral
      Metadata
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      Abstract
      Wheat grain quality and consumption is influenced by its constituents structure and concentrations. In the first part of the dissertation, six Canadian bread wheat cultivars; four (CDC Teal, AC Superb, AC Barrie, AC Splendor) belonging to the Canada Western Red Spring (CWRS), and two (AC Foremost, and AC Crystal) to the Canada Prairie Spring Red (CPSR) market classes were characterized for the relationship between their starch constituents and starch in vitro enzymatic hydrolysis. CPSR cultivars with relatively longer amylopectin chains of DP 37-45, reduced chain lengths of DP 15-18, and a low volume percent of small C-type starch granules, had reduced starch in vitro enzymatic hydrolysis rates. In the second part of the dissertation, near-isogenic wheat lines differing at the Waxy locus were analyzed for the influence of genome-specific granule-bound starch synthase I (GBSSI/Waxy; Wx-A, Wx-B, Wx-D) on starch composition, structure and starch in vitro enzymatic hydrolysis. Amylose concentration was more severely affected in genotypes with GBSSI missing from two genomes (double nulls) than from one genome (single nulls) of wheat, indicating dosage dependent amylose synthesis. Subtle differences in amylopectin chain length distribution were observed among non-waxy, partial and completely waxy starches, suggesting a non-limiting role of genome-specific GBSSI for amylopectin synthesis. A suppressive role of Wx-D on the short chain phenotype of wheat amylopectin was observed. In addition, Wx-D increased the volume percentage of large A-type starch granules and reduced starch hydrolysis index. Thus, among the waxy isoproteins, Wx-D might be the major contributor for reducing the rate of in vitro starch enzymatic hydrolysis in wheat. In the third part of the dissertation, endosperm starch’s physicochemical properties and structure during grain development in wheat waxy-null genotypes were analyzed. The study was conducted with pure starch isolated from wheat grains at 3-30 days post anthesis (DPA), at three day intervals. Changes in amylopectin structure were observed until 12 DPA, suggesting the formation of a basic amylopectin skeleton by this stage. A differential influence of waxy isoproteins on amylopectin structure formation has been suggested, with Wx-B and Wx-D affecting short glucan chains of DP 6-8 at 3 and 6 DPA, Wx-A being effective at 9 and 12 DPA, and Wx-D affecting DP 18-25 chains from 18-30 DPA.
      Degree
      Doctor of Philosophy (Ph.D.)
      Department
      Plant Sciences
      Program
      Plant Science
      Supervisor
      Chibbar, Ravindra N.
      Committee
      Coulman, Bruce; Hucl, Pierre; Bueckert, Rosalind; Van Kessel, Andrew
      Copyright Date
      November 2013
      URI
      http://hdl.handle.net/10388/ETD-2013-11-1291
      Subject
      near-isogenic wheat
      waxy
      amylopectin chain length distribution
      starch hydrolysis
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      • Graduate Theses and Dissertations
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