Sclerotinia stem rot, caused by Sclerotinia sclerotiorum, is a devastating disease in rapeseed. The objective of this study was to investigate the role and the mechanism of silicon (Si) in alleviating the disease severity of S. sclerotiorum in rapeseed. In the absorption assays, the rapeseed that absorbed 10 mM of K2SiO3 exhibited an 86% decrease in lesion size on infected leaves as compared with controls. In the spray assay, the lesion length on rapeseed stems was reduced by 30.5–32.9% with the use of 100 mM of a foliar Si fertilizer as compared with controls. In the pot assay, the lesion length on rapeseed stems was reduced by 34.9–38.3% when using the Si fertilizer as basal fertilizer. In the field assay, both the disease incidence and disease index of sclerotinia stem rot were significantly reduced with the usage of a solid Si fertilizer, Si foliar fertilizer, and the application of both, without negative affection on the main agronomic traits and seed quality of rapeseed. The transcriptome sequencing, quantitative reverse transcription PCR (qRT-PCR), and biochemical assays between K2SO4- and K2SiO3- treated rapeseed leaves revealed that Si promoted the biosynthesis of defense-related substances and enhanced the antioxidation and detoxification abilities of rapeseed after infection. Thus, this study concluded that Si can alleviate the disease severity of S. sclerotiorum in rapeseeds, partially due to the induced defense responses.

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.

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 in orescence (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 in orescence (SNMI) and main in orescence 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 identi ed 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 identi ed a 0.15-Mb interval (25.98-26.13 Mb) from the C06-QTL region aforementioned. Transcriptome sequencing and qRT-PCR identi ed 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. Key MessageGenetic models, QTLs and candidate gene for silique density on main in orescence of rapeseed were identi ed.