Towards the Production of Silique Shatter Resistant Rapeseed By Use of Mutations in Dehiscence Zone Identity Genes

In temperate climate zones, oilseed rape (Brassica napus L., AACC) is an important crop for production of vegetable oil, animal feed and biofuels. The production of rapeseed is limited by its natural propagation system which involves shedding seeds from dry, fragile fruits (siliques). A strategy to reduce pre-harvest seed loss is the manipulation of the silique structure or more specifically, manipulation of the cells forming the predetermined breaking point, the so called dehiscence zone. The development of the dehiscence zone is controlled by a network of transcription factors including SHATTERPROOF1/2 (SHP1/2), INDEHISCENT (IND) and ALCATRAZ (ALC).

Screening a winter rapeseed EMS (ethylmethanesulfonate) mutant population by TILLING identified various mutations in two paralogs of BnIND and BnALC. As in both cases paralogs potentially share redundant functions, single mutations were not expected to show an effect on shatter resistance. For BnIND, phenotyping of greenhouse grown plants confirmed this assumption. Consequently, different mutations were combined by crossing to yield double mutants with more robust siliques. Three different bench top trials proved that a combination of BnIND mutations leads to shatter resistance. Field data obtained from IND mutants sown on two locations in Germany are expected in summer of 2017. In parallel, propagation of BnALC double mutants from the EMS material is in progress. Another approach comprises the targeted mutagenesis of dehiscence zone identity genes by a Cas9-guided RNA.