Identifying new variation at the J locus, previously identified as e6, in long juvenile ‘Paranagoiana’ soybean

KEY MESSAGE: A previously identified soybean maturity locus, E6, is discovered to be J, with the long juvenile allele in Paranagoiana now deemed j−x. ABSTRACT: Soybean grown at latitudes of ~20° or lower can produce lower grain yields due to the short days. This limitation can be overcome by using the long juvenile trait (LJ) which delays flowering under short day conditions. Two LJ loci have been mapped to the same location on Gm04, J and E6. The objective of this research was to investigate the e6 allele in ‘Paranagoiana’ and determine if E6 and J are the same locus or linked loci. KASP markers showed that e6 lines did not have the j−1 allele of LJ PI 159925. A population fixed for E1 but segregating for E6, with e6 introgressed from Paranagoiana, showed single gene control for flowering and maturity under short days. Sequencing Glyma.04G050200, the J gene, with long amplification Taq found that the e6 line ‘Paranagoiana’ contains a Ty1-copia retrotransposon of ~10,000 bp, inserted within exon 4. PCR amplification of the cDNA of Glyma.04G050200 also showed differences between the mRNA sequences (presence of insertion in j−x). Hence, we conclude that the loci E6 and J are one locus and deem this new variation found in Paranagoiana as j−x. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00122-020-03746-2.