Mutations in wheat starch synthase II genes and PCR-based selection of a SGP-1 null line

Area of Science:

• Plant Molecular Biology
• Agricultural Science
• Genetics and Genomics

Background:

• Wheat starch synthase II (SSII), also known as starch granule protein 1 (SGP-1), is crucial for endosperm starch synthesis.
• Three SGP-1 proteins (SGP-A1, SGP-B1, SGP-D1) are encoded by homoeologous SSII genes (wSSII-A, wSSII-B, wSSII-D).
• Null alleles for each SGP-1 protein have been previously identified, indicating genetic variation.

Purpose of the Study:

• To characterize the specific mutations within each wSSII gene in null alleles.
• To develop PCR-based DNA markers for detecting these mutations.
• To demonstrate the utility of these markers in wheat breeding programs.

Main Methods:

• Genetic analysis to identify and characterize mutations in wSSII-A, wSSII-B, and wSSII-D null alleles.
• Development of allele-specific primer sets for PCR-based detection of identified mutations.
• Marker-assisted selection (MAS) to reconstruct a wheat line lacking all three SGP-1 proteins.

Main Results:

• wSSII-A null allele: Characterized by a 289 bp deletion near the initiation codon, with 8 bp of filler DNA.
• wSSII-B null allele: Contains a 175 bp insertion in exon 8, identified as the Hikkoshi miniature inverted-repeat transposable element (MITE).
• wSSII-D null allele: Features a 63 bp deletion at the junction of the fifth exon and intron.
• Developed functional primer sets for allele-specific amplification of each wSSII locus.
• Successfully reconstructed a triple SGP-1 null line using the developed markers and MAS.

Conclusions:

• The characterized mutations and developed DNA markers provide valuable tools for wheat genetics and breeding.
• These markers facilitate marker-assisted selection for precise manipulation of SGP-1 protein content in wheat.
• The developed markers are applicable for breeding programs targeting null, partial, or specific combinations of SGP-1 proteins.