Molecular characterization and marker development of mid-oleic-acid mutant M23 for the development of high-oleic cultivars of soybean

The mid-oleic-acid soybean mutant M23 has been frequently used to develop lines with elevated oleic acid content. M23, which was produced by X-ray irradiation, was previously shown to contain a large deletion including GmFAD2-1a, one of the genes encoding microsomal omega-6 fatty acid desaturase (GmFAD2). However, it was not possible then to develop a codominant marker for the selection of the M23 mutation because the extent of the deletion was unknown. Here, we report that PCR analysis of M23 using published soybean genome sequences as a reference revealed a 164014-bp deletion including GmFAD2-1a and nineteen other predicted genes. We generated a codominant PCR-based marker that can distinguish wild-type/M23 heterozygotes from both homozygous classes. We genotyped F₂ plants segregating for the M23 mutation and confirmed the association of genotype and phenotype. This information will be useful in developing new commercial cultivars of high-oleic-acid soybean. We discuss the possible functions of the genes in the deleted region of M23 in relation to reduced seed yield, which occurs frequently in soybean lines containing the M23 mutation.