Recreating genomically stable rapeseed

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Rapeseed (Brassica napus) is a highly inbred crop species, lacking the substantial genetic diversity required for continuing agricultural improvement. In order to increase genetic diversity in rapeseed, a common method is to recreate this species by making new hybrids between rapeseed progenitor species B. rapa and B. olereacea. These new hybrids have the same chromosome composition as B. napus, as well as increased genetic diversity. However, these hybrids also have unstable genomes due to poor control of meiosis, and lose chromosomes, and hence essential genetic information for plant growth and fertility, from generation to generation. The reason for this genome instability is unknown, particularly since natural B. napus is genomically stable. We suggest that there are two possible hypotheses for this instability in new hybrids. Firstly, this instability could be due to allelic variation within each progenitor species, i.e. genotypic differences in genomic stability, such that the right genetic variants have yet to be combined in human-mediated hybridisation events to produce stable synthetic rapeseed. Secondly, a mutation may have occurred shortly after B. napus formed that enforced genomic stability. We aim to test these hypotheses by investigating genomic stability in a large set (292 lines) of human-made hybrid rapeseed. High-throughput marker genotyping will be used to quantify genomic rearrangements, and fertility and meiotic behavior will be assessed to determine which lines show stable and unstable phenotypes. Identification of the mechanism/s of genomic stability in B. napus will not only provide fascinating insights into the evolutionary history of this species, but will be immediately useful for informing and assisting in transfer of useful genetic diversity into rapeseed.