Characterisation and marker development for low molecular weight glutenin genes from Glu-A3 alleles of bread wheat (Triticum aestivum. L)

PCR was used to amplify low-molecular-weight (LMW) glutenin genes from the Glu-A3 loci of hexaploid wheat cultivars containing different Glu-A3 alleles. The complete coding sequence of one LMW glutenin gene was obtained for each of the seven alleles Glu-A3a to Glu-A3g. Chromosome assignment of PCR products using Chinese Spring nulli-tetrasomic lines confirmed the amplified products were from chromosome 1A. All sequences were classified as LMW-i-type genes based on the presence of an N-terminal isoleucine residue and eight cysteine residues located within the C-terminal domain of the predicted, mature amino acid sequence. All genes contained a single uninterrupted open reading frame, including the sequence from the Glu-A3e allele, for which no protein product has been identified. Comparison of LMW glutenin gene sequences obtained from different alleles showed a wide range of sequence identity between the genes, with between 1 and 37 single nucleotide polymorphisms and between one and five insertion/deletion events between genes from different alleles. Allele-specific PCR markers were designed based on the DNA polymorphisms identified between the LMW glutenin genes, and these markers were validated against a panel of cultivars containing different Glu-A3 alleles. This collection of markers represents a valuable resource for use in marker-assisted breeding to select for specific alleles of this important quality-determining locus in bread wheat.