Abstract

Crambe (Crambe abyssinica Hochst. ex R.E. Fries) is a potential oilseed crop for semiarid and arid environments where saline irrigation waters and soils are common. Crambe tolerance to salinity during germination is unknown. A laboratory experiment was designed to determine salinity tolerance of crambe during germination and salinity ✕ temperature interactions that may influence germination and stand establishment. Treatment solutions were prepared using NaCl and CaCl₂ in a 2:1 molar ratio. Salinity (electrical conductivities of 0.03, 6.3, 12.1, 17.3, 22.5, 27.1, 32.0 and 36.3 dS m⁻¹) and temperature (5, 10, 15, 20, 25 and 30 °C) effects on germination of ‘Meyer’ crambe seed were determined over a 12 d period. Counts were taken at 3 d intervals and germination percentages and rate indexes were determined. Germination declined with increasing salinity at each counting date and salinity ✕ temperature interactions were highly significant. Germination was severely limited at 5 °C with only 22% germination in the salinity control (0.03 dS m⁻¹) after 12 d. The optimum germination temperature for all salinity levels fell in the 15 to 25 °C range, with the final cumulative germination percentage peaking at 20 °C for most treatments. Germination decreased on either side (10 and 30 °C) of the optimum. Germination rate was drastically reduced at 5 °C at all salinity levels, with an intermediate effect at 10 and 30 °C at the lower salinity levels decreasing with increasing salinity at all temperatures. These results suggest that crambe is moderately tolerant to salinity stress during germination over the 10 to 30 °C temperature range.

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