BnKAT2 Positively Regulates the Main Inflorescence Length and Silique Number in Brassica napus by Regulating the Auxin and Cytokinin Signaling Pathways

Exploring silique number in Brassica napus L.: Genetic and molecular advances for improving yield

Silique number is a crucial yield-related trait for the genetic enhancement of rapeseed (Brassica napus L.). The intricate molecular process governing the regulation of silique number involves various factors. Despite advancements in understanding the mechanisms regulating silique number in Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa), the molecular processes involved in controlling silique number in rapeseed remain largely unexplored. In this review, we identify candidate genes and review the roles of genes and environmental factors in regulating rapeseed silique number. We use genetic regulatory networks for silique number in Arabidopsis and grain number in rice to uncover possible regulatory pathways and molecular mechanisms involved in regulating genes associated with rapeseed silique number. A better understanding of the genetic network regulating silique number in rapeseed will provide a theoretical basis for the genetic improvement of this trait and genetic resources for the molecular breeding of high-yielding rapeseed.

Mapping and candidate gene analysis of clustered bud on the main inflorescence in Brassica napus L

Breeding rapeseed varieties with more main inflorescence siliques is an idea for developing rapeseed varieties that are suitable for light and simplified cultivation. The Brassica napus exhibited cluster bud of the main inflorescence (Bnclib) gene. At the fruiting stage, the main inflorescence had more siliques, higher density, and more main inflorescences. Moreover, the top of the main inflorescence bifurcated. Genetic analysis showed that the separation ratio between Bnclib and the wild type in the F₂ generation was 3:1, which indicated that the trait was a single-gene-dominant inheritance. Among the 24 candidate genes, only one gene, BnaA03g53930D, showed differential expression between the groups (False discovery rate, FDR ≤ 0.05, |log2FC|≤ 1). qPCR verification of the BnaA03g53930D gene between Huyou 17 and its Bnclib near-isogenic line showed that BnaA03g53930D was significantly differentially expressed in the stem tissue of Huyou 17 and its Bnclib near-isogenic line (Bnclib NIL). The determination of gibberellin (GA), brassinolide (BR), cytokinin (CTK), jasmonic acid (JA), growth hormone (IAA), and strigolactone (SL) content in the shoot apex of Huyou 17 by Bnclib NIL and wild type showed that all six hormones significantly differed between the Bnclib NIL and Huyou 17. It is necessary to conduct further research on the interactions between JA and the other five hormones and the main inflorescence bud clustering in B. napus.

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

KEY MESSAGE

Genetic 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 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 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.