MOLECULAR CHARACTERIZATION OF THE LOW MOLECULAR WEIGHT GLUTENIN SUBUNIT GENE FAMILY MEMBERS AND THEIR EFFECT ON WHEAT QUALITY
Ibba, Maria Itria
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Gluten is a macro polymer responsible for the unique viscoelastic properties of wheat dough and it is formed from the interaction of wheat seed storage proteins. The low-molecular-weight glutenin subunits (LMW-GSs) are one of the major components of gluten and play a critical role in the determination of wheat end-use quality. However, a clear association between different LMW-GSs and wheat quality is not well understood. The LMW-GSs are in fact hard to differentiate both at genic and protein level. They are encoded by a multigene family located on the short arm of the homoeologous group 1 chromosomes at the Glu-3 loci. The number of LMW-GS genes in each wheat variety differs and there is evidence that genes at each Glu-3 locus are divided by large intergenic and highly recombinogenic regions. Also, LMW-GSs are highly similar in structure among themselves and with many gliadins making them difficult to differentiate at the protein level. For these reasons, the identification of different LMW-GS protein profiles has been challenging, and conflicting results on the association between LMW-GS alleles and wheat end-use quality have been reported. The objective of this project was to develop a better understanding of the genetics of the LMW-GSs and of the role that each LMW-GS gene has in the determination of wheat end-use quality. First a set of common wheat varieties identified as standards for the Glu-3 alleles were analyzed for their LMW-GS genic profile to verify whether there was an association between a specific genic profile and the relative Glu-3 allele. Then, the genetic linkage between the LMW-GS genes at each Glu-3 locus was investigated to develop a better understanding of the Glu-3 loci structure. The results obtained from the two previous analyses were used to better interpret and characterize the LMW-GS profile of a set of elite bread wheat varieties and to correlate specific LMW-GS genes to different dough rheology parameters. Finally, a set of molecular markers specific for each LMW-GS haplotype was developed to facilitate the analysis of the LMW-GSs in wheat breeding programs. Results of this project will greatly improve the current knowledge of the LMW-GSs.