Genetic variance for flowering time conferring E2 gene in photoperiod-insensitive early-maturing soybean accessions and topological distribution in Korea peninsula

Soybean [ Glycine max (L.) Merr.] is one of the major legume crops for human and livestock, and the double cropping system with soybean have been widely applied to increase arable land utilization rate. To employ the soybean for multiple cropping system, cultivars, which are photoperiod insensitive and early maturing, are required. The region-specific crop adaptation could be achieved by the successful flowering followed by progeny production, and it is important to understand the mechanisms underlying the transition from the vegetative to reproductive stage. In soybean, 10 genes/QTLs conferring flowering time were identified, and four genes, E1 , E2 , E3 , and E4 , are mainly involved in geographic adaptation of soybean. Here, to develop the photoperiod-insensitive early-maturing soybean varieties, QTL analysis was conducted using RILs from the crosses between photoperiod-insensitive early-maturing soybean cultivar, Keunol, and late maturity soybean cultivar, Sinpaldal. Furthermore, to identify the topological distribution within Korea peninsula, SNPs in exon region of 40 soybean varieties were investigated by sequencing of the exon region in E2 and comparing to their origin information. The results showed that early flowering is mainly controlled by the E2 in five different environments, and there are three nonsynonymous SNPs in E2 . Two of them, SNPs in exon 2 and 10, produce the premature stop codon. The first SNP in exon 2 was strongly linked to topological distribution, which is mainly restricted to southern area of Korea peninsula. This result could provide the useful information to develop photo-insensitive early-maturing soybean cultivar, which could be employed in various cropping system.