Field-based screening and haplotyping of J locus for long juvenile trait in tropical soybean genotypes

The long juvenile trait influences flowering time of soybean under tropical conditions. The trait ensures sufficient vegetative growth prior to flowering. The present study aimed at identifying tropical soybean genotypes with the long juvenile trait and harboring the loss-of-function alleles for the J gene and verifying the effect of loss-of-function alleles on the long juvenile trait.

A total of 159 soybean genotypes were evaluated on the field for two years in tropical city of Sanya, Hainan Islands, China for days to beginning bloom (VE-R1), days to physiological maturity (VE-R7), nodes/plant, pods/plant and plant height at maturity. The full length of the J gene was cloned in the 159 soybean genotypes. The sequence data was subjected to haplotype analysis to determine the genotypes with the functional and loss of function alleles.

Significant differences (p<0.05) were observed among genotypes for all phenotypic traits. 53 genotypes were identified with delayed flowering based on the phenotypic data. Sequence comparison of the 159 genotypes identified 10 polymorphisms comprising 7 SNPs and three deletions in the coding sequences, the three deletions resulted in the loss of function of the J gene. Six genotypes with delayed flowering had the loss-of-function alleles of the J gene.