Oilseed rape: learning about ancient and recent polyploid evolution from a recent crop species

Abstract

Oilseed rape (Brassica napus) is one of our youngest crop species, arising several times under cultivation in the last few thousand years and completely unknown in the wild. Oilseed rape originated from hybridisation events between progenitor diploid species B. rapa and B. oleracea, both important vegetable species. The diploid progenitors are also ancient polyploids, with remnants of two previous polyploidisation events evident in the triplicated genome structure. This history of polyploid evolution and human agricultural selection makes B. napus an excellent model with which to investigate processes of genomic evolution and selection in polyploid crops. The ease of de novo interspecific hybridisation, responsiveness to tissue culture, and the close relationship of oilseed rape to the model plant Arabidopsis thaliana, coupled with the recent availability of reference genome sequences and suites of molecular cytogenetic and high-throughput genotyping tools, allow detailed dissection of genetic, genomic and phenotypic interactions in this crop. In this review we discuss the past and present uses of B. napus as a model for polyploid speciation and evolution in crop species, along with current and developing analysis tools and resources. We further outline unanswered questions that may now be tractable to investigation.

CRISPR/Cas9-mediated genome editing efficiently creates specific mutations at multiple loci using one sgRNA in Brassica napus

“…Development of new oilseed cultivars using traditional cross-breeding strategies is time-consuming and complicated because they are allotetraploids 3–5 . Therefore, new breeding technologies that can introduce one or a few traits into an elite background would appear useful for developing new cultivars of oilseed rape.…”

Mapping of homoeologous chromosome exchanges influencing quantitative trait variation in Brassica napus

“…Genomic positions in the B. napus reference genome sequence were assigned to all tested SNP markers showing a BLAST hit with the SNP flanking sequences, as described previously (Qian et al, 2014;Mason and Snowdon, 2016). In brief, SNP markers were physically localized on the Brassica napus Darmor-bzh reference genome sequence assembly (version 4.1) (Chalhoub et al, 2014) using the following criteria: minimum overlap of 50-bp length, minimum identity of 95%, no sequence gaps.…”

Creating favourable morphological and yield variations for rapeseed by interspecific crosses between Brassica rapa and Brassica oleracea

“…Phenotypic variations of floral, flowering traits, plant height, photosynthetic capability, grain quality and strip rust resistance have also been revealed in wheat hybrids (Langer, Longin, & Wurschum, ; Liu, Song, Zhang, Yang, & Hu, ; Tikhenko, Rutten, Tsvetkova, Voylokov, & Borner, ). However, these phenotypic variation are difficult to be easily used in rapeseed breeding, due to the genomic instability during early polyploidization (Gaeta & Pires, ; Mason & Snowdon, ; Szadkowski et al., ). Thus, it will be helpful to adopt sequencing and molecular methods to find the candidate genes with putative functions on branch variation and yield improvement, using the resynthesized B. napus in this research.…”

“…Phenotypic variations of floral, flowering traits, plant height, photosynthetic capability, grain quality and strip rust resistance have also been revealed in wheat hybrids (Langer, Longin, & Wurschum, 2014;Liu, Song, Zhang, Yang, & Hu, 2017;Tikhenko, Rutten, Tsvetkova, Voylokov, & Borner, 2015). However, these phenotypic variation are difficult to be easily used in rapeseed breeding, due to the genomic instability during early polyploidization (Gaeta & Pires, 2010;Mason & Snowdon, 2016;Szadkowski et al, 2011).…”