New genetic variation for silique shatter resistance in rapeseed
A major issue in rapeseed cultivation is the pre-harvest seed loss. The fruits, so called siliques, dry out at maturity and become very fragile. Bad weather conditions as strong winds or hail can cause the siliques to break and shed the seeds. This does not only result in yield loss but the shattered seeds can also survive in the soil and germinate during the next growing seasons. During crop-rotation those volunteer plants are regarded as weeds. If the farmer decides to grow another rapeseed variety in the same field, volunteer plants of an inferior variety can reduce the quality of the harvest.
A network of transcription factors is involved in the development of the predetermined breaking point of the silique, the dehiscence zone. Knock-out mutations of INDEHISCENT (IND) and ALCATRAZ (ALC) produced shatter resistant fruits in Arabidopsis (Rajani and Sundaresan 2001; Liljegren et al. 2004).
We are aiming at the production of shatter resistant rapeseed by the use of mutations in paralogs of IND and ALC. The objectives of this work are to obtain mutants both from an EMS (ethylmethanesulfonate) mutant population by conventional TILLING and from a targeted mutagenesis approach with a CRISPR/Cas9 system. Selected mutations will be combined by crossing and the resulting double mutant lines will be analyzed for shatter resistance. Three bench top phenotyping methods will be compared with pre-harvest seed loss data collected from field experiments.
Prior to this work, a winter rapeseed TILLING resource was established by chemical mutagenesis with EMS (Harloff et al. 2012). TILLING fragments were designed to cover BnaA.IND.a, BnaC.IND.a, BnaA.ALC.a and BnaC.ALC.a. Among 3488 M2 plants we identified mutations of various kinds.
Shatter resistance measurements of M4-5 BnIND single mutants did not show an improvement of silique robustness. This was expected as B. napus houses two IND paralogs with supposedly redundant functions. However, combining different mutations by crossing to create double mutants resulted in significantly increased shatter resistance. For siliques obtained from the greenhouse, this tendency was consistent for three different phenotyping methods. To validate that two combined IND mutations can reduce pre-harvest losses in rapeseed, a field trial was sown on two locations in Germany in late summer of 2016.
Production of BnALC double mutants from the EMS material is currently in progress. In parallel, we are working on targeted mutagenesis of shatter resistance genes.
Prof. Dr. Stanislav Gorb, Dr. Lars Heepe, Zoological Institute, Functional Morphology and Biomechanics, Kiel University
Institute of Clinical Molecular Biology (IKMB), Kiel University
Norddeutsche Pflanzenzucht Hans-Georg Lembke KG
NPZ Innovation GmbH
SAATEN-UNION BIOTEC GmbH
Posters and Oral Presentations
Braatz J., Emrani N., Harloff H.-J., Jung C. (2016) Increasing seed shatter resistance in oilseed rape (B. napus L.) by TILLING and CRISPR/Cas9 mutagenesis, 2nd Sino-German Rapeseed Symposium, Kiel, 23.-26.05.2016. Oral Presentation.
Braatz J., Emrani N., Harloff H.-J., Jung C. (2016) Comparing seed shatter resistance in mutants of oilseed rape (B. napus L.), German Plant Breeding Conference, Bonn, 08.-10.03.2016. Poster.
Braatz J., Emrani N., Harloff H.-J., Jung C. (2016) Erzeugung von Ölraps mit erhöhter Schotenplatzfestigkeit, 66. Öffentliche Hochschultagung der Agrar- und Ernährungswissenschaftlichen Fakultät, Kiel, 04.02.2016. Poster.
Harloff H.-J. (2015) Verbesserung der Schotenplatzfestigkeit in Raps, GFP Jahrestagung Öl- und Eiweißpflanzen, Bonn, 04.11.2015. Oral Presentation.
Braatz J., Emrani N., Harloff H.-J., Jung C. (2015) Seed shattering resistance in mutants of oilseed rape (B. napus L.), 18th Genome Research GPZ-Conference, Düsseldorf, 22-24.09. 2015. Oral Presentation.
Funding has been provided by the Stiftung Schleswig-Holsteinische Landschaft under grant No. 2013/69
Updated: 31.08.2016 Responsible for this webpage: J. Braatz