Location: Cereal Crops ResearchTitle: New DNA Markers for High Molecular Weight Glutenin Subunits in Wheat) Author
Submitted to: Theoretical and Applied Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/30/2008
Publication Date: 9/17/2008
Publication URL: parking.nal.usda.gov/shortterm/20179___226519.pdf
Citation: Liu, S., Chao, S., Anderson, J.A. 2008. New DNA Markers for High Molecular Weight Glutenin Subunits in Wheat. Theoretical and Applied Genetics. 118:177-183 Interpretive Summary: End-use quality is one of the priorities of modern wheat breeding. Although inheritance of wheat quality traits are complex, high molecular weight (HMW) glutenins, a type of storage protein found in wheat grains, were previously found to play a major role in determining the bread making quality of wheat. The DNA sequences for genes encoding HMW glutenins have been well characterized. Previous reports have showed that DNA markers can be developed based on the known sequences and used in breeding programs to assist breeders in selecting breeding lines potentially carrying good quality traits through a lab process known as marker-assisted selection (MAS). In order to efficiently carry out MAS in the lab, high throughput genotyping techniques capable of processing a large number of samples are required. However, most of the previously reported DNA markers were found to be inadequate for genotyping using modern automated equipment. Therefore, the objective of this study was to develop and validate DNA markers suitable for high throughput MAS for HMW glutenins encoded by genes located on chromosomes 1A and 1D in wheat. We first used a set of 16 wheat cultivars carrying known HMW glutenins to determine if the DNA markers developed in this study could accurately predict their corresponding genes. Our results showed the three markers developed in this study, UMN19 associated with the 1A genes, and UMN25 and UMN26 associated with the 1D genes, matched perfectly with their known protein types. These three markers were then used to successfully genotype breeding populations of a total of 1,536 individuals following the high throughput genotyping process developed in our lab.
Technical Abstract: End-use quality is one of the priorities of modern wheat breeding. Even though quality is a complex trait, high molecular weight (HMW) glutenins play a major role in determining the bread making quality of wheat. DNA markers developed from the sequences of HMW glutenin genes were reported in several previous studies to facilitate marker-assisted selection (MAS). However, most of the previously available markers are dominant and amplify large DNA fragments, and thus are not ideal for genotyping using modern equipment. The objective of this study was to develop and validate co-dominant markers suitable for high throughput MAS for HMW glutenin subunits encoded at the Glu-A1 and Glu-D1 loci. Indels were identified by sequence alignment of allelic HMW glutenin genes, and were targeted to develop locus-specific co-dominant markers. Marker UMN19 was developed by targeting an 18-bp deletion in the coding sequence of subunit Ax2*. A single DNA fragment was amplified by marker UMN19, and was placed onto chromosome 1AL. Sixteen wheat cultivars of known HMW glutenin subunits were used to validate marker UMN19. The cultivars with subunit Ax2* amplified the 362-bp fragment as expected, and the 344-bp fragment was observed for cultivars with subunit Ax1 or the Ax-null allele. Two co-dominant markers UMN25 and UMN26 were developed by targeting the fragment size polymorphic sites between subunits Dx2 and Dx5, and between Dy10 and Dy12, respectively. The 16 wheat cultivars with known HMW glutenin subunit composition were genotyped with markers UMN25 and UMN26, and the genotypes perfectly matched their subunit types. Four F2 populations segregating for the Glu-A1 or Glu-D1 loci were successfully genotyped with UMN19, UMN25, and UMN26 using fluorescent labeling of PCR products separated and analyzed with the Applied Biosystems 3130xl Genetic Analyzer.