Flour proteins linked to quality traits in an Australian doubled haploid wheat population

The Cranbrook/Halberd doubled haploid population has provided a unique oppo rtunity to examine in detail the contributions made by a number of differen t high molecular weight (HMW) and low molecular weight (LMW) glutenin allel es to the dough properties in a set of homogeneous lines of wheat. A range of different instruments was employed, including Farinograph, Extensograph, Do-Corder, Resistograph, and GRL/EasyMix, to study the dough rheology of t he lines from 3 sites over 2 years. Correlation studies showed that 2 basic parameters (dough strength and extensibility) were measured by these diffe rent instruments. The results presented are mainly from the Extensograph, w hich is a major Australian standard for determining release and marketing c lassification of Australian wheats. Approaches to investigate the data include bulk segregant analysis, distrib ution of protein alleles in the population, and multiple linear regression. As expected, the HMW glutenin alleles made a major contribution to dough s trength, with a minor, but not insignificant, contribution from the LMW glu tenin alleles. From a knowledge of their glutenin alleles, a glutenin stren gth score (GSS) was devised to allow breeders to rank the dough strength of various lines. The GSS scoring system is based on both HMW and LMW gluteni n alleles, adding to a total out of 10. Extensibility, on the other hand, w as predominantly influenced by protein levels in the flour and environmenta l conditions such as site and season. However, the LMW glutenin alleles mak e a significant genetic contribution to the extensibility, which can be ass essed by using a glutenin extensibility score. These two glutenin quality s cores currently include only the alleles present in the parents, Cranbrook and Halberd, but this could be expanded to include a wider range of alleles by analysis of the quality data from other doubled haploid populations. Th ese quality scores would then be an extremely useful tool for assessing the potential quality of parental and early generation germplasm in wheat bree ding programs, by a knowledge of the allelic composition of their HMW and L MW glutenins.