Genetic and molecular analysis of fasciation mutation in Japanese soybeans

Soybean fasciation is controlled by a recessive gene affecting the shape of the aerial parts of the plant, which is characterized by flattened stem, infrequent branches and clustering of flowers and pods on shoot apices. Morphological feature of the fasciation mutation has been dissected, but molecular information is still limited. We developed three populations derived from the crosses between wild type cultivars and three Japanese fasciation varieties, Shakujodaizu, Taikadaizu and Shakujomame, respectively. The molecular mapping of the three F2 populations revealed that the fasciation locus (F locus) was mapped on the chromosome 2 (LG D1b). Fine mapping experiment with a population consisting of 1536 seeds derived from the F2 lines segregating for fasciation revealed that a DNA marker cosegregated with the fasciation phenotype. This DNA marker was dominant for wild type allele and the flanking region of this marker could not be amplified in Shakujodaizu as well as in the other two fasciation varieties, suggesting that some deletion or major rearrangement probably occurred at the f allele. Genomic information disclosed two predicted genes, Glyma02g36940 and Glyma02g36960, that were annotated in the vicinity of this DNA marker. The relationship between these candidate genes and the fasciation phenotype was discussed.