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

Abstract 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 P1 (an inbreed line with high SDMI), P2 (an inbreed line with low SDMI), F1, F2, 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 P1 and P2 by using a genetic linkage map constructed by 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.