| Hard Red Spring wheat (Triticum aestivum L.) is used primarily for the production of leavened dough products. To produce good quality bread with high loaf volume and regular crumb texture, dough must retain intact gas cells for as long as possible during proofing and baking. Loaf volume is under partial genetic control and is affected by flour composition and dough rheological properties. To develop wheat cultivars with improved bread-making quality, breeders need screening methods which can predict loaf volume accurately, have high heritability, and rank genotypes similarly among environments. Tests must also be quick and simple. As more knowledge is gained on mechanisms that control bread-making quality, new testing methods are designed. Because the environment has a large influence on end-use quality, methods must be evaluated over several locations and years to determine whether they can be used for selection. A multi-environment trial was conducted which included 19 genotypes grown at 7 locations from 2006 to 2009. Commonly used screening tests such as sodium dodecyl sulfate sedimentation, mixograph and glutomatic tests were performed. In addition, two newer methods, the mixolab and Kieffer dough extensibility (KDE) tests were evaluated. Baking tests were performed at the USDA Hard Red Spring Wheat Quality Laboratory, in Fargo, ND. Results showed that environment affected all tests and their relationships with loaf volume indicating that breeding lines should be evaluated in several environments, regardless of testing method. Mixolab was able to differentiate genotypes based on their mixing and pasting properties. However, peak viscosity was the only pasting property to significantly affect loaf volume. No variable measured with any method was highly correlated with loaf volume. No method could predict loaf volume with R2 higher than 0.50. However, by averaging genotypes over environments and including hardness index in the model, good predictions were obtained with R2 values that ranged from 0.68 to 0.85. Some variables were identified which should be useful for selection. Use of mixolab and KDE tests for selection did not appear to be better than mixograph and glutomatic tests when the aim was to predict loaf volume. Some environmental conditions increased loaf volume and dough extensibility measured with the KDE tests even for genotypes lacking dough strength. The role of genotype and environment on flour, dough, and baking characteristics, as well as their interrelationships, are reported in this dissertation and represent valuable information for breeders and end-users. |
