QTL Mapping and Diurnal Transcriptome Analysis Identify Candidate Genes Regulating Brassica napus Flowering Time.

Chaozhi Ma,Kaining Hu,Chenjian Zhuo,Jinxiong Shen,Jurong Song,Jing Wen,Yanke Cui,Bao Li,Bin Yi,Yuanguo Gu,Jinxing Tu,Tingdong Fu

doi:10.3390/ijms22147559

Abstract

Timely flowering is important for seed formation and maximization of rapeseed (Brassica napus) yield. Here, we performed flowering-time quantitative trait loci (QTL) mapping using a double haploid (DH) population grown in three environments to study the genetic architecture. Brassica 60 K Illumina Infinium™ single nucleotide polymorphism (SNP) array and simple sequence repeat (SSR) markers were used for genotyping of the DH population, and a high-density genetic linkage map was constructed. QTL analysis of flowering time from the three environments revealed five consensus QTLs, including two major QTLs. A major QTL located on chromosome A03 was detected specifically in the semi-winter rapeseed growing region, and the one on chromosome C08 was detected in all environments. Ribonucleic acid sequencing (RNA-seq) was performed on the parents’ leaves at seven time-points in a day to determine differentially expressed genes (DEGs). The biological processes and pathways with significant enrichment of DEGs were obtained. The DEGs in the QTL intervals were analyzed, and four flowering time-related candidate genes were found. These results lay a foundation for the genetic regulation of rapeseed flowering time and create a rapeseed gene expression library for seven time-points in a day.

Highlights

Published: 15 July 2021Rapeseed (Brassica napus), known as oilseed rape or canola, is a major oil crop globally and the third-largest source of vegetable oil after soybean and palm (USDA, 2019, https://www.ers.usda.gov/data-products/oil-crops-yearbook/, last accessed date12 September 2020)
Combined with Ribonucleic acid sequencing (RNA-seq) analysis at multiple sampling time-points, we identified potential candidate flowering-time genes that could enrich the understanding of the rapeseed flowering-time regulatory network and provide a genetic basis for advances in rapeseed flowering-time research
At seven time-points (Table S6, Figure S2). These results indicated that our RNA-seq data were highly reliable and could be used for subsequent analysis

Summary

Introduction

Published: 15 July 2021Rapeseed (Brassica napus), known as oilseed rape or canola, is a major oil crop globally and the third-largest source of vegetable oil after soybean and palm (USDA, 2019, https://www.ers.usda.gov/data-products/oil-crops-yearbook/, last accessed date12 September 2020). Rapeseed is classified as winter, spring, and semi-winter types based on vernalization requirement differences. The semi-winter and spring types are the main types planted in China, of which the semi-winter type is primarily planted in the Yangtze. River basin and the spring type in the northern region. Flowering indicates the plant has completed its conversion from the vegetative stage to the reproductive stage, and it is essential for plant reproduction and crop yield formation [2]. By adjusting rapeseed flowering time, it can be adapted to farming systems in different regions to maximize planting area and yield [3,4]. Flowering time is an important trait to be considered in rapeseed breeding.

Methods

Results

Conclusion