Geographical distribution of GmTfl1 alleles in Chinese soybean varieties

Stem growth habit is an important agronomic trait in soybean and is subject to artificial selection. This study aimed to provide a theory for genotypic selection of stem growth habit for breeding purposes by analyzing the alleles of GmTfl1 gene in Chinese soybean varieties and establishing a database of GmTfl1 variation. Using knowledge of insertion and deletion (Indel) in the non-coding region and four single-nucleotide polymorphisms (SNPs) in the coding sequences of the GmTfl1 gene, four CAPS and one Indel markers were developed and used to test 1120 Chinese soybean varieties. We found that the dominant GmTfl1 allele was prevalent in accessions from the Northern ecoregion, whereas the recessive allele, Gmtfl1, was more common in the Southern ecoregion, and the proportions of GmTfl1 and recessive alleles were respectively 40.1% and 59.9% in the Huang-Huai ecoregion. The proportion of GmTfl1 decreased and that of Gmtfl1 increased, gradually from north to south. Allele GmTfl1-a was present in higher proportions in the Huang-Huai spring, Huang-Huai summer, and Northern spring sub-ecoregions than that in the other sub-ecoregions. GmTfl1-b was common in the Northeast spring, Northern spring and Southern summer sub-ecoregions. Gmtfl1-ta was found mainly in the Huang-Huai spring, Huang-Huai summer and Southern spring sub-ecoregions. The Gmtfl1-ab allele was distributed in all six soybean sub-ecoregions. The Gmtfl1-bb allele was distributed mainly in the Huang-Huai spring and summer and Southern spring and summer sub-ecoregions, but the Gmtfl1-tb allele was detected only in the Huang-Huai summer sub-ecoregion. The distributions of GmTfl1 and Gmtfl1 have shown no large changes in nearly 60 years of breeding, but the frequency of the recessive genotype Gmtfl1 has shown a rising trend in the last 20 years. This study provides a theoretical foundation for breeding new soybean varieties for different ecoregions.