Influence Of Wheat Low-molecular-weight Glutenin Subunit Allelic Variation On SDS Sedimentation Volume And Solvent Retention Capacity

The low-molecular-weight glutenin subunit (LMW-GS) accounts for approximately one-third of wheat (Triticum aestivum L.) total seed storage proteins. Their ability to form inter-molecular disulphide bounds with each other and/or with high-molecular-weight glutenin subunit (HMW-GS), is important for the formation of the glutenin polymers which determine the processing properties of wheat dough. LMW-GS are a highly polymorphic protein complex encoded by a multigene family. However, due to the complexity of the LMW-GS composition and the genetically close linkages between Glu-3 and Gli-1 loci, it is difficult in separating single components, characterising individual proteins and establishing clear-cut relationships with quality parameters.The development of molecular marker system well makes up for the shortage of previous methods. This molecular marker system are available for accurate and efficient characterisation of LWM-GS genes on a large scale and useful in marker-assisted breeding programmes for the improvement of wheat quality. To understand the effect of LMW-GS allelic variation at Glu-A3 and Glu-B3 loci on the sodium dodecyl sulfate (SDS) sedimentation volume and solvent retention capacity (SRC) values, a large experiment was carried out with 244 accessions of Chinese wheat mini core collections by means of developed LMW-GS allelic molecular marker system. The results are as following.1. The collection of 244 wheat varieties using Glu-A3 allele-specific markers were conformed as seven alleles (Glu-A3a, Glu-A3b, Glu-A3c, Glu-A3d, Glu-A3e, Glu-A3f and Glu-A3g). Among all the alleles, the Glu-A3a possessed the highest proportion (29.5%). It was followed by the Glu-A3c (23.4%). The lowest frequency was found for the Glu-A3f (3.7%). The frequency of Glu-A3b, Glu-A3d, Glu-A3e and Glu-A3g was 11.5%,12.7%, 11.5% and 7.8% respectively.2. The distribution of ten alleles (Glu-B3a, Glu-B3b, Glu-B3c, Glu-B3d, Glu-B3e, Glu-B3f, Glu-B3g, Glu-B3h, Glu-B3i and Glu-B3j) of 244 wheat varieties were determined by Glu-B3 allele-specific markers. Among all the varieties, main alleles included Glu-B3a (13.9%), Glu-B3d (11.9%), Glu-B3g (12.3%) and Glu-B3i (22.1%). Only six varieties, consisting of 1 landrace,2 improved and 3 introduced varieties, carrying the Glu-B3h possessed the lowest proportion (2.5%).3. The most wide range of SDS sedimentation volume varing from 13.5 mL to 55.5 mL was present across 28 wheat varieties carrying Glu-A3b, while the most narrow range from 8.0 mL to 31.8 mL was observed in 19 wheat varieties carrying Glu-A3g. The GIu-A3 locus could explain 12.8% of the variance in SDS sedimentation volume, which was predominantly affected by the alleles Glu-A3b, Glu-A3d and Glu-A3g at 0.01 level. The results regarding SRC (water SRC, lactic acid SRC, sodium carbonate SRC and sucrose SRC) showed, the greatest means among whole meal flour water SRC, lactic acid SRC and sodium carbonate SRC values were observed in the group with the allele Glu-A3b except sucrose SRC value, for which 9 varieties carrying the allele Glu-A3f possessed the greatest. The explanatory part of variance analysis of Glu-A3 was only 4.7%for lactic acid SRC, which was lower than 6.4% for sucrose SRC. The lactic acid SRC varied significantly between 28 wheat varieties carrying the allele Glu-A3b and 19 wheat varieties carrying the allele Glu-A3g at 0.05 level. Unexpectedly, Glu-A3f giving the highest mean (129.6 g kg-1) produced an extremely pronounced effect on the sucrose SRC, resulting in significant increase in sucrose SRC value by comparison to the total average (124.4 g kg-1) at 0.01 level.4. The range of SDS sedimentation volume among 244 wheat varieties was 8.0-55.5 mL. The most wide range of SDS sedimentation volume was present both across 26 wheat varieties carrying Glu-B3f and across 54 wheat varieties carrying Glu-B3i, while the most narrow range from 13.5 mL to 32.0 mL was observed in 11 wheat varieties carrying Glu-B3c. The Glu-B3 locus could explain 8.1% of the variance in SDS sedimentation volume, which was predominantly affected by the alleles Glu-B3c and Glu-B3h at 0.01 level. The results regarding SRC test showed, the greatest means among whole meal flour lactic acid SRC, sodium carbonate SRC and sucrose SRC were observed in the group with the allele Glu-B3e, while the lowest means among whole meal flour lactic acid SRC, sodium carbonate SRC and sucrose SRC were observed in the group with the allele Glu-B3g.