Quantitative variation of total and individual high molecular weight glutenin subunits of wheat in relation to variation in environmental conditions

The total amount of the high molecular weight glutenin (HMWg) subunits, and the amount of the individual subunits, present in kernels of wheat (Triticum aestivum L) were studied in relation to differences in growing conditions. The amounts of individual HMWg subunits in four varieties, each grown at six sites in The Netherlands, differed considerably between the sites. Only to a limited extent (0-66%, depending on variety) could this variation be ascribed to differences in protein content of the samples. The cause of the rest of the variation is unknown. Accordingly, the total amount of the HMWg subunits, relative to the total amount of proteins present in a wholemeal flour of a variety, differs between the samples produced at different sites. Thus the preference for synthesis of a certain protein fraction may, vary depending on the environment. A second experiment showed that variation in protein contents of samples of two varieties grown on the same trial field accounted for about 90% of the variation in the total amount of HMWg subunits. The samples of each variety differed in protein content as a result of differences in the amount of N fertiliser applied. Within each variety, the ratio between the individual HMWg subunits was less dependent on variations in environmental conditions than on the actual amount, indicating that the levels of expression of the individual HMWg subunit genes are regulated by a common mechanism. The implications of the results for the selection possibilities of wheat with desired bread-making quality and for studies concerning genetic variation in the amount of HMWg subunits are discussed.