Genetic analysis and QTL mapping for silique density in rapeseed (Brassica napus L.)

Key messageGenetic models, QTLs and candidate gene for silique density on main inflorescence of rapeseed were identified.Silique density is one of the critical factors to determine seed yield and plant architecture in rapeseed (Brassica napus L.); however, the genetic control of this trait is largely unknown. In this study, the genetic model for silique density on main inflorescence (SDMI) of rapeseed was estimated according to the phenotypic data of P-1 (an inbreed line with high SDMI), P-2 (an inbreed line with low SDMI), F-1, F-2, BC1P1 and BC1P2 populations, revealing that SDMI is probably controlled by multi-minor genes with or without major gene. The QTLs for SDMI and its component characters including silique number on main inflorescence (SNMI) and main inflorescence length (MIL) were consequently mapped from a DH population derived from P-1 and P-2 by using a genetic linkage map constructed by restriction site-associated DNA sequencing (RAD seq) technology. A total of eight, 14 and three QTLs were identified for SDMI, SNMI and MIL under three environments, respectively, with an overlap among SDMI and SNMI in 55.7-75.4 cm on linkage group C06 which corresponding to 11.6-27.3 Mb on chromosome C06. Genomic resequencing was further conducted between a high- and a low-SDMI pool constructed from the DH population, and QTL-seq analysis identified a 0.15 Mb interval (25.98-26.13 Mb) from the C06-QTL region aforementioned. Transcriptome sequencing and qRT-PCR identified one possible candidate gene (BnARGOS) from the 0.15 Mb interval. This study will provide novel insights into the genetic basis of SD in rapeseed.

Automated summary

This study identified the genetic control of silique density on the main inflorescence of rapeseed, revealing the involvement of both minor and major genes. QTL analysis and genomic resequencing identified several QTL regions associated with silique density, with overlap between silique number on the main inflorescence and silique density. Transcriptome sequencing and qRT-PCR identified one candidate gene (BnARGOS) from a specific QTL region.