Identifying Unique Combinations of Starch and Protein Genes Optimizing Functional Wheat Flour Tortilla Quality.

Wheat flour tortillas require unique functional properties such that the starch characteristics of the flour may impact this functionality as much, or more than protein characteristics. Although the flour starch components and their impact on tortilla quality have not been studied to the same extent as the protein components, low levels of amylose starch often produce a softer final product, and hence, low amylose may optimize functional tortilla quality. Deletion mutants of the Granule-Bound Starch Synthase (GBSS) genes in wheat genotypes result in flour with less amylose starch. The number of null GBSS genes characterizes full or partial waxy genotypes, where any of one or two null GBSS genes are considered partial waxy genotypes. We propose that specific combinations of glutenin protein subunits and null GBSS genes can be produced to optimize functional flour tortilla quality. Thus, our objectives are to develop wheat genotypes each with unique combinations of null GBSS genes and protein glutenin subunits and to identify those genetic combinations that optimize functional wheat flour tortilla quality. Twenty-two wheat genotypes with different glutenin subunits were hybridized to one full waxy wheat genotype, and doubled-haploid (DH) lines are being produced from F₁ and F₂ progeny to fix these gene combinations in a homozygous state. To genotype the parents and DH lines, SDS-PAGE and STS markers are being used to determine the presence of glutenin subunits and waxy mutations, respectively. Tortillas produced from flour milled from seed of DH lines, each having unique glutenin and waxy combinations will be evaluated for functional tortilla quality. Thus far, 14 sets of GBSS STS primers successfully characterized unique genotypes with various null GBSS mutations, and these are in the process of being fixed as homozygous DH lines.