QTL mapping for long juvenile trait in soybean accession AGS 25 identifies association between a functional allele of FT2a and delayed flowering

Soybean is a quantitative photoperiod sensitive short-day crop. In Asian countries, soybean is grown under rain-fed conditions. However, late planting due to delayed onset of the rainy season results in the reduced biomass leading to considerable yield losses. Long juvenility (LJ) trait in soybean delays flowering and helps in gaining biomass under short days. Our objective of this work was to understand the molecular basis of long juvenility in a genetic resource AGS 25. In this study, we used recombinant inbred lines (RILs) developed from an LJ genotype AGS 25 and conventional juvenile (CJ) genotype JS 93–05 and mapped a major quantitative trait locus (QTL) explaining upto 39.7% of the phenotypic variation. The identified QTL carried two candidate flowering genes FT2a and FT2b, in which genomic DNA sequencing of coding DNA sequence identified the former with a functional SNP variation but the latter was found monomorphic. The identified mutation in FT2a could be associated with LJ and validated in another segregating population (F 2 of SL 958 × AGS 25). The novel mutation caused a non-synonymous substitution of conserved glycine with aspartic acid (G169D) and the mechanism of LJ through this mutation is to be further divulged. This identified mis-sense mutation found associated with delayed flowering in two previous reports. The identified new functional SNP created differential HinfI (e9-CAPS) restriction sites and high-resolution melt (HRM) profiles (e9-HRM) for CJ and LJ parents and are associated with delayed flowering in RILs and F 2 population (SL 958 × AGS 25).