Mapping of Quantitative Trait Loci Associated with Terminal Raceme Length in Soybean

Abstract

ABSTRACTSoybean [Glycine max (L.) Merr.] develops inflorescence meristems on each node, including the shoot apex. The flower clusters of the soybean raceme have a highly branched inflorescence structure, and their racemes are classified as terminal, primary, secondary, and so on. Raceme phenotype is an important trait associated with the number of floral buds and pods, and is dependent on the genotype. The breeding line 1532–1 was characterized by remarkably long racemes at the shoot apex of the main stem. To identify quantitative trait loci (QTLs) conditioning the terminal raceme length (TRL), a recombinant inbred line (RIL) population was developed from a cross between 1532–1 and an ordinary cultivar, Toyoharuka. The RILs were divided into two groups according to their alleles for a maturity locus, E1. The early‐maturing RIL group with the e1 genotype was used for QTL analysis of TRL, while the late‐maturing RIL group with the E1 genotype could not mature normally and lodged severely. Analysis of the early‐maturing group resulted in the identification of a stable QTL, qTRL18–1, where the 1532–1 allele had a positive effect on TRL. Another QTL, qTRL11–1, was detected only in the RILs with the 1532–1 alleles at the qTRL18–1 locus, indicating an interaction between qTRL18–1 and qTRL11–1. The qTRL18–1 locus was located in the proximal region of the Dt2 locus. No stable QTLs for flowering time or maturing time were detected in the proximal region of qTRL18–1 or qTRL11–1. Our results provide a new strategy to increase pod number on the main stem by marker‐assisted selection (MAS) for qTRL18–1 and qTRL11–1.