HPLC AND IMMUNOASSAY-BASED GLUTENIN SUBUNIT ANALYSIS - SCREENING FOR DOUGH PROPERTIES IN WHEATS GROWN UNDER DIFFERENT ENVIRONMENTAL-CONDITIONS

The relationship between dough properties, loaf parameters and data from three approaches [HPLC, immunoassay and high M(r) glutenin subunit quality score (determined by SDS-polyacrylamide gel electrophoresis)] were compared in order to assess both their relative values in quality screening, and to determine the relationships between the parameters. Total high M(r) and low M(r) glutenin subunits were quantified by reversed-phase HPLC in two sets of flour samples: (1) 27 wheal cultivars grown at each of three Australian sites in 1989; and (2) 14-15 cultivars grown at one site in 1986 under three levels of nitrogen fertilisation. The sets of samples were also analysed using two antibody assays, the results of which had earlier been shown to provide correlations with dough strength. With each set of samples, antibody binding, the amounts of high M(r) glutenin subunits and high M(r) glutenin subunit quality scores were each correlated to a similar extent with maximum resistance. In contrast, Farinograph dough development time was much more closely related to high M(r) glutenin subunit content and antibody binding than high M(r) glutenin subunit composition. This is probably due to the former two measures taking into account environmental effects as well as genotype. Extensibility tended to be related to the total amount of glutenin subunits and its major components, the low M(r) glutenin subunits. When grouped across sites and nitrogen fertiliser treatments, these trends were less apparent because of the dominant effect of variation in protein content. Statistical incorporation of the effect of variation in flour protein content improved prediction of maximum resistance but not loaf volume. Total gliadin content only maintained correlations with dough development time, which was also consistently correlated with flour protein content. The studies confirm earlier immunoblotting and ELISA data suggesting that the antibody assays selectively quantify high M(r) glutenin subunits. They also indicate differential relationships between particular gluten protein fractions and theological parameters, such as strength and extensibility.