A Modified Method to Assess Secondary Dormancy in the Seeds of Different Rapeseed Lines and Cultivars

The exposure of seeds to undesirable soil conditions induces secondary dormancy and this causes many problems for seed producers. Assessing seed secondary dormancy potential is an important factor in developing rapeseed lines and cultivars. A relatively rapid, precise, and reproducible method derived from the Hohenheim standard dormancy test (HSDT) has been developed for secondary dormancy evaluation of 41 rapeseeds (Brassica napus L.) lines and 5 cultivars. The two previous methods, HSDT and rapid secondary dormancy (RDT) were compared with our suggested fast-reproducible dormancy test (FRDT) method. All three methods consider three stages for seeds i.e. dormancy induction, germination in darkness, and breaking secondary dormancy. In the FRDT method, time to germination in darkness and seed dormancy breakage duration decreased to 7 and 4 days, respectively, whereas the corresponding figures in the HSDT were 14 and 7 days. Meanwhile, the duration of the three stages in sum decreased from 35 to 25 days. The obtained ranges of seed dormancy in different lines and cultivars as assessed by HSDT, FRDT, and RDT varied from 6 to 98.75, 7.5 to 99, and 0 to 36%, respectively. Positive relationships were found between data of the seed secondary dormancy testing by HSDT and FRDT methods. Owe to the precise and reproducible estimates, both HSDT and FRDT methods can be used for testing seed secondary dormancy in different rapeseed lines and cultivars. This method helps seed breeders to improve the screening of new rapeseed lines and cultivars with lower potential for secondary dormancy and as a result reduce the risk of volunteer rapeseed.