Abstract

The dough properties of flours from the grain of 172 doubled haploid lines of a Cranbrook Halberd cross, grown at 3 locations, were determined with traditional and small-scale dough testing equipment. The experiments were aimed at determining the genetic factors that underpin the flour processing properties of wheat flour. Seven mixing parameters determined on a 2-g Mixograph™, as well as the maximum resistance (RMAX) and extensibility (EXT) measured on a Micro-Extension Tester, were identified as quality traits for genetic mapping studies, to identify the underlying quantitative trait loci (QTL). For each of the 3 locations in which the wheat lines were grown, relationships between the quality parameters and genetic markers were constructed for the populations. The associations of HMW- and LMW-glutenin allele combinations with the quality traits were investigated using ANOVA, linear parametric, and non-parametric methods. Of particular interest were qualitative and quantitative assessments of the extremes of the quality traits in each population. The relative contributions of the glutenincoding loci to quality were determined and it was found that the growing conditions to which wheat lines were subjected significantly affected the analyses. The nature and extent of these variations could not be explained by changes in protein content alone, and were related to environmentally induced alterations in the protein composition. From a comparison of the measurements made with the small-scale Mixograph™ with those from both the Extensograph™ and a Micro-Extension Tester, it was concluded that the same information about RMAX and EXT obtained from traditional extension testing could be obtained using small-scale dough tests. The data provided a direct validation for the application of small-scale testing for the screening of large populations. The comparisons of large and small scale testing procedures also provided the basis defining a new trait, ‘M-extensibility’, which is obtained from protein content and selected Mixograph data. This parameter was able to be measured more accurately and was shown to be closely related to the traditional extensibility measurement, and thus very useful for molecular/genetic analysis. The M-extensibility trait could be mapped as a major QTL to LMW-glutenin subunit loci on chromosomes 1B and 1D.