Identification of a major QTL and candidate genes analysis for branch angle in rapeseed (Brassica napus L.) using QTL-seq and RNA-seq.

Introduction: Branching angle is an essential trait in determining the planting density of rapeseed (Brassica napus L.) and hence the yield per unit area. However, the mechanism of branching angle formation in rapeseed is not well understood. Methods: In this study, two rapeseed germplasm with extreme branching angles were used to construct an F2 segregating population; then bulked segregant analysis sequencing (BSA-seq) and quantitative trait loci (QTL) mapping were utilized to localize branching anglerelated loci and combined with transcriptome sequencing (RNA-seq) and quantitative real-time PCR (qPCR) for candidate gene mining. Results and discussion: A branching angle-associated quantitative trait loci (QTL) was mapped on chromosome C3 (C3: 1.54-2.65 Mb) by combining BSA-seq as well as traditional QTL mapping. A total of 54 genes had SNP/Indel variants within the QTL interval were identified. Further, RNA-seq of the two parents revealed that 12 of the 54 genes were differentially expressed between the two parents. Finally, we further validated the differentially expressed genes using qPCR and found that six of them presented consistent differential expression in all small branching angle samples and large branching angles, and thus were considered as candidate genes related to branching angles in rapeseed. Our results introduce new candidate genes for the regulation of branching angle formation in rapeseed, and provide an important reference for the subsequent exploration of its formation mechanism.

Layered Niobium Oxide Hydrate Anode with Excellent Performance for Lithium-Ion Batteries.

Benefiting from the advantages of cost-effectiveness and sustainability, lithium-ion batteries (LIBs) are recognized as a next-generation energy technology with great development potential. Herein, niobium oxide hydrate (H3ONb3O8) synthesized by a facile and inexpensive solvothermal method is proposed as the anode of LIBs. It is a layered two-dimensional material composed of negatively charged two-dimensional lamellae and positively charged interlayer hydronium ions. The former consist of NbO6 octahedral units connected by bridging oxygen. Because of the mutual effect of hydronium ions and niobium oxide quantum dots, niobium oxide hydrate exhibits excellent electrochemical activity when used as an anode material. This compound is first applied to lithium-ion batteries, obtaining a high specific capacity (1232 mAh g-1) at 100 mA g-1 and maintaining an outstanding performance after 200 cycles. Therefore, this work not only proposes a simple preparation method of niobium oxide hydrate but also expands the variety of high-performance anode materials.

Superior lithium-storage properties derived from a g-C3N4-embedded honeycomb-shaped meso@mesoporous carbon nanofiber anode loaded with Fe2O3 for Li-ion batteries.

In this work, a honeycomb-shaped meso@mesoporous carbon nanofiber material incorporating homogeneously dispersed ultra-fine Fe2O3 nanoparticles (denoted as Fe2O3@g-C3N4@H-MMCN) is synthesised through a pyrolysis process. The honeycomb-shaped configuration of the meso@mesoporous carbon nanofiber material derived from a natural bio-carbon source (crab shell) acts as a support for an anode material for Li-ion batteries. Graphitic carbon nitride (g-C3N4) is produced via the one-step pyrolysis of urea at high temperature under an N2 atmosphere without the assistance of additives. The resulting favorable electrochemical performance, with superior rate capabilities (1067 mA h g-1 at 1000 mA g-1), a remarkable specific capacity (1510 mA h g-1 at 100 mA g-1), and steady cycling performance (782.9 mA h g-1 after 500 cycles at 2000 mA g-1), benefitted from the advantages of both the host material and the Fe2O3 nanoparticles, which play an important role due to their ultra-fine particle size of 5 nm. The excellent cycle life and high capacity demonstrate that this strategy of strong synergistic effects represents a new pathway for pursuing high-electrochemical-performance materials for lithium-ion batteries.

Screening of clubroot-resistant varieties and transfer of clubroot resistance genes to Brassica napus using distant hybridization.

Clubroot is an economically important disease affecting plants in the family Cruciferae worldwide. In this study, a collection of 50 Cruciferae accessions was screened using Plasmodiophora brassicae pathotype 4 in China. Eight of these demonstrated resistance, including three Chinese cabbages, two cabbages, one radish, one kale, and one Brassica juncea. The three clubroot-resistant Chinese cabbages (1003, 1007 and 1008) were then used to transfer the clubroot resistance genes to B. napus by distant hybridization combined with embryo rescue. Three methods including morphological identification, cytology identification, and molecular marker-assisted selection were used to determine hybrid authenticity, and 0, 2, and 4 false hybrids were identified by these three methods, respectively. In total, 297 true hybrids were identified. Clubroot resistance markers and artificial inoculation were utilized to determine the source of clubroot resistance in the true hybrids. As a result, two simple sequence repeat (SSR) and two intron polymorphic (IP) markers linked to clubroot resistance genes were identified, the clubroot resistance genes of 1007 and 1008 were mapped to A03. At last, 159 clubroot-resistant hybrids were obtained by clubroot resistance markers and artificial inoculation. These intermediate varieties will be used as the 'bridge material' of clubroot resistance for further B. napus breeding.

Genetic mapping of a lobed-leaf gene associated with salt tolerance in Brassica napus L.

Lobed leaf is a common trait, which is related with photosynthesis and plant stress resistance in crops. In order to fine map and isolate the lobed-leaf gene in Brassica napus, an F2:3 population derived from 2205 (salt tolerance) and 1423 (salt sensitive) was constructed, and the quantitative trait locus (QTL) technology was adopted to identify the QTLs related to lobed leaf formation. As a result, one major QTL was identified on LG10, and two intron polymorphic (IP) markers and one sequence characterized amplified region (SCAR) marker were successfully developed in QTL region. The lobed-leaf gene was mapped to a region from 15.701 to 15.817 M on A10. In light of annotations of the genes in candidate region, a leaf morphological development related gene, Bra009510, was primary identified as the candidate gene. The full length of the candidate gene was 1390 bp containing three exons and two introns in the two parents. The open reading frame (ORF) was 693 bp and encoded a protein of 229 amino acids. Eight amino acid differences between the two parents in CDS (coding sequences) region were identified. qRT-PCR analysis showed that the expression of the candidate gene was significantly different between the two parents under salt stress. These results showed that the candidate gene might be related to leaf morphological development and abiotic stresses. Our study will lay a solid foundation for studying lobed leaf mechanism in B. napus L.

Quantitative Trait Locus Mapping of Salt Tolerance and Identification of Salt-Tolerant Genes in Brassica napus L.

Salinity stress is one of typical abiotic stresses that seriously limit crop production. In this study, a genetic linkage map based on 532 molecular markers covering 1341.1 cM was constructed to identify the loci associated with salt tolerance in Brassica napus. Up to 45 quantitative trait loci (QTLs) for 10 indicators were identified in the F2:3 populations. These QTLs can account for 4.80-51.14% of the phenotypic variation. A major QTL, qSPAD5 on LG5 associated with chlorophyll can be detected in three replicates. Two intron polymorphic (IP) markers in this QTL region were developed successfully to narrow down the QTL location to a region of 390 kb. A salt tolerance related gene Bra003640 was primary identified as the candidate gene in this region. The full length of the candidate gene was 1,063 bp containing three exons and two introns in B. napus L. The open reading frame (ORF) is 867 bp and encodes 287 amino acids. Three amino acid differences (34, 54, and 83) in the conserved domain (B-box) were identified. RT-qPCR analysis showed that the gene expression had significant difference between the two parents. The study laid great foundation for salt tolerance related gene mapping and cloning in B. napus L.