Qiong Hu

Summary Allotetraploid oilseed rape ( Brassica napus L.) is an agriculturally important crop. Cultivation and breeding of B . napus by humans has resulted in numerous genetically diverse morphotypes with optimized agronomic traits and ecophysiological adaptation. To further understand the genetic basis of diversification and adaptation, we report a draft genome of an Asian semi‐winter oilseed rape cultivar ‘ ZS 11’ and its comprehensive genomic comparison with the genomes of the winter‐type cultivar ‘Darmor‐ bzh ’ as well as two progenitors. The integrated BAC ‐to‐ BAC and whole‐genome shotgun sequencing strategies were effective in the assembly of repetitive regions (especially young long terminal repeats) and resulted in a high‐quality genome assembly of B . napus ‘ ZS 11’. Within a short evolutionary period (~6700 years ago), semi‐winter‐type ‘ ZS 11’ and the winter‐type ‘Darmor‐ bzh ’ maintained highly genomic collinearity. Even so, certain genetic differences were also detected in two morphotypes. Relative to ‘Darmor‐ bzh ’, both two subgenomes of ‘ ZS 11’ are closely related to its progenitors, and the ‘ ZS 11’ genome harbored several specific segmental homoeologous exchanges ( HE s). Furthermore, the semi‐winter‐type ‘ ZS 11’ underwent potential genomic introgressions with B . rapa (A r ). Some of these genetic differences were associated with key agronomic traits. A key gene of A03. FLC 3 regulating vernalization‐responsive flowering time in ‘ ZS 11’ was first experienced HE , and then underwent genomic introgression event with A r , which potentially has led to genetic differences in controlling vernalization in the semi‐winter types. Our observations improved our understanding of the genetic diversity of different B . napus morphotypes and the cultivation history of semi‐winter oilseed rape in Asia.

Rapeseed (Brassica napus L.) is the largest oilseed crop in China and accounts for about 20% of world production. For the last 10 years, the production, planting area, and yield of rapeseed have been stable, with improvement of seed quality and especially seed oil content. China is among the leading countries in rapeseed genomic research internationally, having jointly with other countries accomplished the whole genome sequencing of rapeseed and its two parental species, Brassica oleracea and Brassica rapa. Progress on functional genomics including the identification of QTL governing important agronomic traits such as yield, seed oil content, fertility regulation, disease and insect resistance, abiotic stress, nutrition use efficiency, and pod shattering resistance has been achieved. As a consequence, molecular markers have been developed and used in breeding programs. During 2005–2014, 215 rapeseed varieties were registered nationally, including 210 winter- and 5 spring-type varieties. Mechanization across the whole process of rapeseed production was investigated and operating instructions for all relevant techniques were published. Modern techniques for rapeseed field management such as high-density planting, controlled-release fertilizer, and biocontrol of disease and pests combined with precision tools such as drones have been developed and are being adopted in China. With the application of advanced breeding and production technologies, in the near future, the oil yield and quality of rapeseed varieties will be greatly increased, and more varieties with desirable traits, especially early maturation, high yield, high resistance to biotic and abiotic stress, and suitability for mechanized harvesting will be developed. Application of modern technologies on the mechanized management of rapeseed will greatly increase grower profit.

Rapeseed (Brassica napus L.) is a very important edible oil crop in the world, and the production is inhibited by abiotic stresses, such as salinity. Plant hormones can alleviate the stress by regulating the physiological processes and gene expression. To study the plant responses to salinity in combination with GR24, a synthesized strigolactone, the oilseed rape variety (Zhongshuang 11, ZS 11) replications were grown in the pots in a controlled growth chamber under three levels of salinity (0, 100, and 200 mM NaCl) and 0.18µM GR24 treatments at the seedling stage for 7d. The results showed that salinity depressed the shoots and roots growth, whereas GR24 improved the growth under salt stress. Leaf chlorophyll contents, gas exchange parameters (Pn, Gs, Ci and Tr) were also reduced significantly with increasing salinity, and these effects could be partially reversed by GR24 application. Additionally, GR24 treatment significantly increased and decreased the PSII quantum yield (Y(II)) and non-photochemical fluorescence quenching (NPQ) respectively under salinity stress conditions. The activities of peroxidase (POD) and superoxide dismutase (SOD) increased, and lipid peroxidation measured by the level of malondialdehyde (MDA) reduced due to GR24 application. The transcriptome analysis of root and shoot was conducted. 342 common differentially expressed genes (DEGs) after GR24 treatment and 166 special DEGs after GR24 treatment under salinity stress were identified in root and shoot. The DEGs in root were significantly more than that in shoot. qPCR validated that the stress alleviation was mainly related to the gene expression of tryptophan metabolism, plant hormone signal transduction and photosynthesis.