Canola response to high and moderately high temperature stresses during seed maturation

Canola is a valuable oilseed crop worldwide. Temperature during the post-anthesis period plays an important role in determining the final yield and seed composition. Experiments were conducted in climate-controlled growth cabinets to test the effect of two high temperature regimes following a 24-h acclimation period on three canola cultivars differing in their thermotolerance. A long, moderately high temperature treatment of 28°C/23°C (day/night) was applied for 10 d from 20 to 30 d after flowering (DAF) and a short, very high temperature regime of 28°C/23°C (day/night) including a peak of 38 °C reached for 5 h around midday for 5 d from 25 to 29 DAF. Very high temperature for 5 d reduced yield on the main stem by up to 52% for a sensitive cultivar by reducing seed weight. This treatment also decreased the oil/protein ratio, but had a lesser effect on fatty acid composition. The moderately high temperature treatment for 10 d had only affected yield of one cultivar and increased the oil/protein ratio of all cultivars. However, it had a more pronounced effect on the fatty acid profile. A short period of very high temperature at a sensitive stage can be as critical to canola mild temperature stress over a longer period. Key words: Brassica napus, oil, protein, fatty acids, tolerance, acclimation, heat stress