Quantitative trait loci (QTL) mapping and doubled haploid technology for spring wheat improvement

  • Author / Creator
    Asif, Muhammad
  • Efficiency is important in wheat breeding programs. A series of studies were conducted to determine genetic differentials, map genomic regions affecting various agronomic and quality traits in conventional and organic management systems and to improve doubled haploid (DH) technology in spring wheat. A mapping population developed from a cross between Attila x CDC Go performed differently in the two management systems. Heritability estimates differed between systems for five of the nine traits including grain yield, tillers, plant height, kernel weight and grain protein content. Direct selection in each management system resulted in 50% or less lines selected in common for eight of the nine (except for flowering time) traits. Overall, we mapped 46 QTL for various agronomic and quality traits across organic and conventional management systems for three years. Most of these QTL were specific to the management systems; however, consistent QTL for grain yield, test weight, kernel weight and days to flowering were mapped in both systems on chromosomes 6A, 1B, 3A and 5B, respectively. These consistent QTL also behaved differently in both systems with respect to their phenotypic variation and additive effects leading to the conclusion that selection and testing of genotypes for production and quality traits should be done within environmental conditions which are comparable to where candidate lines are intended to perform. The technique of isolated microspore culture (IMC) is being used in many species to produce DH plants; however, low frequency of green plant production, microbial contamination and albinism limit its use in wheat breeding programs. A series of experiments were conducted to improve microspore embryogenesis. In four different experiments, induction medium (NPB-99+10% Ficoll) was supplemented with various organelle antioxidants, antibiotics and phytosulfokine alpha (PSK-α) along with optimization of induction medium osmolality. Glutathione (2 µM), PSK-α (10-7 M) and osmolality of induction medium at 350 mOsm kg-1 enhanced the efficiency of microspore embryogenesis in wheat and triticale. Cefotaxime at 100 and 50 mg L-1 also helped to control recurrent bacterial contamination in our laboratory, reduce the occurrence of albinism and substantially increase the formation of embryo/embryo like structures and green plant production in wheat and triticale, respectively. The systematic use of these treatments in IMC of wheat and triticale is recommended.

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    Doctor of Philosophy
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