Fatty acids composition of oilseed rape genotypes as affected by solar radiation and temperature

Environmental parameters are known to affect the fatty acid profiles of oilseed crops. Whereas the role of temperature in fatty acid desaturation is well documented, the impact of solar radiation, and therefore photosynthetic activity, is less known. Moreover, the interaction between temperature and solar radiation has rarely been documented. This study is based on field data and an experiment under semi-controlled conditions. The first experiment in growth chambers was designed to assess independently the impact of light intensity and temperature; the analysis of the data from field experiments with natural variation in solar radiation and temperature showed their relation to the alpha-linolenic acid concentration (C18:3) at different growth stages. Temperature affected the fatty acid composition, by increasing the oleic acid concentration (C18:1) and decreasing the C18:3. The results validated with more years and genotypes that the period from 680 to 930°-days after onset of flowering (DDAF) was sensitive to the minimum temperatures. Solar radiation during seed filling was also found to be negatively correlated with C18:3. However, during an earlier sensitive period, from 100 to 300 DDAF, solar radiation had a positive impact on C18:3 concentration. These seemingly contradictory effects could be the consequence of the impact of solar radiation on the source-sink ratio, with a higher source-sink ratio leading to lower C18:3 concentration. Moreover, our data showed that the response of the C18:3 concentration to solar radiation and temperature depended on the genotype with a tendency to less intense effects on high-oleic low-linolenic (HOLL) genotypes. As a result of these findings, an empirical model with solar radiation from 100 to 300 DDAF and the minimum temperature from 680 to 930 DDAF, with genotype-dependent sensitivity, was proposed to predict C18:3.