Secondary dormancy inBrassica napusis correlated with enhancedBnaDOG1transcript levels

Abstract Dormancy has evolved in plants to restrict germination to favourable growth seasons. Seeds from most crop plants have low dormancy levels due to selection for immediate germination during domestication. Seed dormancy is usually not completely lost and low levels are required to maintain sufficient seed quality. Brassica napus cultivars show low levels of primary seed dormancy. However, B. napus seeds are prone to the induction of secondary dormancy, which can lead to the occurrence of volunteers in the field in subsequent years after cultivation. The DELAY OF GERMINATION 1 ( DOG1 ) gene has been identified as a major dormancy gene in the model plant Arabidopsis thaliana . DOG1 is a conserved gene and has been shown to be required for seed dormancy in various monocot and dicot plant species. We have identified three B. napus genes with high homology to AtDOG1 , which we named BnaA.DOG1.a , BnaC.DOG1.a and BnaC.DOG1.b . The transcripts of these genes could only be detected in seeds and showed a similar expression pattern during seed maturation as AtDOG1 . In addition, the BnaDOG1 genes showed enhanced transcript levels after the induction of secondary dormancy. These results suggest a role for DOG1 in the induction of secondary dormancy in B. napus .