Hydrotime Analysis of Ethiopian Mustard (Brassica carinata A. Braun) Seed Germination Under Different Temperatures

Ethiopian mustard (Brassica carinata A. Braun) is an oil‐seed species that has recently become an object of great interest as a promising crop for energy purposes (biodiesel and biolubricant production). In semi‐arid regions of South Italy, soil moisture at sowing time is often inadequate, delaying and reducing seed germination. In this study, the effect of reduced water potential on seed germination in three cultivars of B. carinata (ISCI 7, CT 180 and Sincron) was investigated in the laboratory. Germination behaviour at constant temperatures under low water availability was also analysed through the hydrotime model. Six water potentials (ψ_s) in PEG solution (0, ?0.2, ?0.4, ?0.6, ?0.8 and ?1.0 MPa) and three temperatures (10, 20 and 30 °C) were used for the germination tests. A thermo‐inhibiting effect was observed at the highest levels of water stress. The hydrotime analysis revealed that the increase of temperature to 30 °C reduced predicted hydrotime (θ_H) by hastening the rate of germination, but shifted median base water potential (ψ_b(50)) to higher values (less negative), whereas the lowering of temperature increased θ_H. These observations may have a great agronomic impact because although fewer seeds germinated at 30 °C at the highest levels of water stress, they may germinate faster in rapidly drying soil. However, genetic differences were observed among cultivars in terms of estimated θ_H and ψ_b(50). The hydrotime modelling approach offered in this study may help predict B. carinata seed germination under soil water deficit conditions occurring under early or late autumnal sowing.