Seed Priming with Erucic Acid or Glucosinolates Enhances Germination and Cold Tolerance in Rapeseed

Low temperature during germination of late-seeded rapeseed disrupts multiple physiological and biochemical processes and thus limits growth and yield. Accordingly, methods to improve cold tolerance in late-sown rapeseed are needed. In this study, Zhongshuang 11 seeds were primed for 10 h with different concentrations of erucic acid (EA) or glucosinolates (GSLs). After drying, seeds were germinated at low temperature (15 °C/10 °C, 16 h/8 h light/dark) for 14 days. Compared with the control (distilled water priming), the optimal treatments—500 mg/L EA and 300 mg/L GSLs—increased germination rates by 2.9% and 15.6%, respectively, and raised total seedling biomass by 14–24%. Physiological assays on day 14 showed that EA priming increased peroxidase (POD) activity by 28.3%, while GSL priming enhanced superoxide dismutase (SOD) and POD activities by 12.6% and 36.2%, respectively. EA seed priming increased auxin (IAA), brassinolide (BR), cytokinin (CTK), and gibberellin (GA) contents in underground tissues by 37.2%, 18.7%, 53.9%, and 46.7%, respectively, while GSL priming raised IAA, BR, and GA levels in aerial tissues by 74.0%, 59.0%, and 26.6%. Moreover, EA seed priming significantly increased the activities of long-chain acyl-CoA synthetase (LACS) and carnitine acyltransferase (CPT) in rapeseed seedlings, whereas GSL priming elevated glutathione S-transferase (GST) and thioredoxin reductase (TrxR) activities. Field experiments confirmed that EA and GSL priming enhanced seedling biomass accumulation, producing 31.4% and 23.8% increases in total dry weight, respectively, and increased silique number per plant by 15.6% and 17.3%, ultimately raising grain yield by 12.9% and 20.0%. These results indicate that EA or GSL seed priming can improve cold tolerance and yield of late-seeded rapeseed, although further multi-environment and mechanistic studies are required.