Genetic diversity of wheat storage proteins and bread wheat quality

To understand the genetic and biochemical basis of the bread making quality of wheat varieties a large experiment was carried out with a set of 162 hexaploid bread wheat varieties registered in the French or European Wheat Catalogue. This material was used to analyse their allelic composition at the twelve main storage protein loci. A large genetic and biochemical diversity of the gluten proteins was found. Several gliadin encoding loci exhibited the highest allelic diversity whereas the lowest diversity was found for Glu-A1 and Glu-D3 loci encoding some high molecular weight glutenin subunits (HMW-GS) and LMW-GS respectively. The varieties were grown in three experimental locations in France. Quality evaluation was carried out from material harvested in each location using seven technological tests: grain protein content (Prot), grain hardness (GH), Zeleny sedimentation test (Zel), Pelshenke test (Pel), water soluble pentosans (relative viscosity: Vr), mixograph test (giving 11 parameters) and the alveograph test (dough strength W, tenacity P, extensibility L, swelling G, ratio Pn and the elasticity index Ie). Genetic and location effects as well as broad-sense heritability of each of the 22 technological parameters were calculated. GH. corresponding to the major Ha gene, Pel, and MtxW (mixograph parameter) had the highest heritability coefficients, alveograph parameters like W, P, the relative viscosity Vr and several mixograph parameters had medium heritability coefficients whereas Prot and L had the lowest. Variance analysis (using GLM procedure) allowed the effect of the allelic diversity of the storage proteins, on the genetic variations of each quality parameters, to be estimated. Glu-1 and Glu-3 loci had significant additive effects in the genetic variations of many parameters. Gliadin alleles encoded at Gli-1 and Gli-2 were also found to play significant effect on several quality parameters. The major part of the phenotypic variation of the different quality parameters like Zel, Pel, W or mixograph peak time MPT was explained with the GH and alleles encoded at Glu-1 and Glu-3. Allelic variants encoded at Glu3 and Gli-2 had similar contribution to the phenotypic variations of quality parameters and accounted for 4% up to 21% each.