Research and development towards a laboratory method for testing the genotypic predisposition of oilseed rape (Brassica napus L.) to secondary dormancy

Oilseed rape (OSR) genotypes having low predisposition to secondary dormancy can reduce agronomic problems arising with volunteers from persistent seeds, and contribute to gene containment if genetically modified cultivars are grown. This study introduces a standardized laboratory method (HSDT; 35 days) for testing the predisposition of OSR to secondary dormancy (genotypic dormancy potential). Additionally, a rapid test (RDT; 21 days) was developed for fast and easy screening. Both methods consisted of three steps: dormancy induction, germination test, and viability test of potentially dormant seeds. Twenty three OSR cultivars were tested by both methods. Dormancy levels ranged between 4 and 95% (HSDT) and between 3 and 89% (RDT). Dormancy was higher in the HSDT than in the RDT, but the strong correlation between the methods (R-2 = 0.95) suggested that both methods are suitable to determine the genotypic dormancy potential. Reduction of analysis time by another 7 days was possible by omission of the viability test without affecting the results. The reduction of sample size from 100 to 50 seeds per replicate proved to be a further option to decrease analysis effort. Standardization is necessary to directly compare results from different working groups and to obtain reliable results for further research. The rapid method enables breeders and scientists to easily screen great numbers of individual plants, lines or cultivars to identify genotypes having low predisposition to secondary dormancy.