Insights into temperature effects on the fatty acid composition of oilseed rape varieties

Conventional oilseed rape (OSR) and high-oleic low-linolenic (HOLL) varieties were compared for their temperature sensitivity during 10 years of variety testing in Switzerland. A high variability in alpha-linolenic acid (ALA) content among locations and years was noticed for both types of varieties (6.3% to 11.4% for conventional varieties, 2.1% to 4.6% for HOLL ones). Average minimum temperature was registered during seed filling, between 680° and 930° days after the onset of flowering. They ranged from 9.2 °C and 17.5 °C and were negatively correlated to ALA content in the seeds at harvest. Additionally to lower ALA contents, HOLL varieties had a smaller response to temperature, as compared to conventional cultivars. When studying each variety independently, small but significant differences appeared among varieties of the same group (HOLL or conventional). Among conventional varieties, differences were observed only in oleic acid desaturation, whereas linoleic acid desaturation efficiency was similar for the studied cultivars. Conversely, in HOLL varieties, linoleic acid desaturation was reduced by mutations and not affected by temperature, resulting in lower ALA content and a lower sensitivity to temperature. Each OSR variety could be characterized by the regression parameters for their specific response to minimum temperature in the adequate period, with two distinct groups for conventional and HOLL varieties. A single model for each variety group was built to predict ALA content at harvest, based simply on minimal temperature during the period. The model was then tested on an independent data set. Combinations with the model BRASNAP-PH to predict onset of flowering made it possible to simulate ALA content without field observations, knowing only sowing date and meteorological data. A sensitivity analysis was performed to determine which precision was required on flowering date and the importance of knowing cultivar characteristics. Our results showed that ALA content prediction was possible, although flowering date was only estimated with a precision of 3 days. In spite of differences among varieties for their temperature sensitivity (R2 varying from 0.39 to 0.89 among tested varieties), a general equation can give a satisfying prediction for conventional varieties within the observed range of temperature, (y = −0.41x + 13.7, with x = minimum temperature registered during the sensitive period, R2 = 0.52, p < 0001). Therefore, using this general model could be used to test the potential of a new production site or assess the quality variability upon time or among different locations.