Dadachamame (named after a combination of the local dialect for 'dad' and 'bean'), cultivated in Tsuruoka City, Yamagata Prefecture, is widely known as a delicious edamame with strong umami and sweetness and a pleasant aroma. The good taste of this bean is said to be caused by its abundance of free amino acids and sucrose compared to general edamame, but the reason why these taste-enhancing components accumulate in such high concentrations in the seeds has remained unknown.
Graduate Student Naohiro Shioya of the United Graduate School of Agricultural Sciences at Iwate University (assigned to Yamagata University), Professor Tomoki Hoshino of the Graduate School of Agricultural Sciences at Yamagata University, and Associate Professor Eri Ogiso of the Department of International Environmental and Agricultural Science, the Graduate School of Agriculture at Tokyo University of Agriculture and Technology have independently cultivated a large-scale hybrid population of 344 lines by crossing and self-pollinating soybeans and Dadachamame.
By investigating the DNA and free amino acid content of each line, they discovered that tof11, a loss-of-function variant of the TOF11 (Time of Flowering 11) gene that is known for controlling flowering and ripening in soybeans, increases the free amino acid content in edamame and improves its taste. This marks the world's first successful proof of the secret behind Dadachamame's deliciousness at the genetic level. This study demonstrates the potential for further improving the taste of Dadachamame in the future. The findings were published in Theoretical and Applied Genetics.
The research group adopted a molecular genetic approach to identify the genes determining the taste of Dadachamame. Specifically, using "Enrei," a common soybean variety widely cultivated in Japan, and "Shirayama," the most famous strain of Dadachamame, as research materials, they cultivated a novel recombinant inbred line (ES_RIL) population through eight generations of self-pollination after crossing the two.
This ES_RIL population was cultivated on a large scale over three years at the experimental farm of the Field Science Center, Faculty of Agriculture, Yamagata University, and edamame was harvested by line. Subsequently, the free amino acid content in the harvested edamame seeds was measured.
At the same time, DNA was extracted from the ES_RIL seeds using an independently developed method (the IMP Boom method), and the DNA of each line was examined using a next-generation sequencer (NGS).
The results obtained were integrated to determine where on the chromosome the quantitative trait locus (QTL) that cause high accumulation of free amino acids are located by QTL analysis.
As a result, they successfully mapped the QTL associated with free amino acid accumulation in Dadachamame 11_1 (qAAD11_1) on a chromosome. This qAAD11_1 was located in the same chromosomal region as the QTL for days to flowering in Dadachamame 11 (qDFD11), which determines the flowering date.
When the researchers performed whole-genome resequencing of Enrei and Shirayama using NGS and compared their DNA of qAAD11_1, they identified TOF11, known for controlling flowering and ripening in soybeans, as the candidate gene for qAAD11_1. Furthermore, they discovered that compared to Enrei carrying the normal TOF11, an Enrei mutant carrying the mutated tof11 not only reaches flowering and the edamame stage earlier but also has a significantly higher free amino acid content in the edamame.
From these results, it was proven that the gene responsible for qAAD11_1 is TOF11. It was found that Shirayama, a type of Dadachamame, possesses the loss-of-function tof11, which increases the free amino acid content in the edamame and enhances its taste.
It was also found that Shirayama, a type of Dadachamame, possesses qAAD11_2. Conversely, this lowers free amino acid content in the vicinity of qAAD11_1, which causes a high accumulation of free amino acids. By improving this qAAD11_2, it may be possible to make Shirayama even more delicious in the future.
Journal Information
Publication: Theoretical and Applied Genetics
Title: Loss-of-function allele of the soybean flowering/maturation gene TOF11 increases free amino acid content at the edamame stage and improves eating quality
DOI: 10.1007/s00122-026-05205-w
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