Fatty acid compositions of triacylglycerols in flax (Linum usitatissimum L.) seeds with varied seeding dates and nitrogen fertilization in a temperate region of Japan

We monitored fatty acid compositions of the triacylglycerol (TAG) fractions in flax (Linum usitatissimum L.) seeds cultivated in pots with different seeding dates and nitrogen (N) fertilizing conditions in a temperate region Wakayama, Japan. Five flax cultivars were seeded in early and late December 2017, and in late January 2018, and matured in May, June and July in the order of planting. Three types of N fertilizer were applied for plants seeded in January. Fatty acid profiles in seed TAG fractions were varied among the cultivation conditions. A cluster analysis dissected the fatty acid profiles of the same genotype with different seeding dates. Principal component analyses revealed inverse correlations between saturated and unsaturated fatty acid contents, which could be affected by temperature, N fertilization, and genotypic factors. The highest correlation was observed between α-linolenic and oleic acid contents, which showed a strong inverse relationship across genotypes (r= 0.964, n = 15). The ratio of α-linolenic acid content to that of oleic acid in seeds from plants seeded in early December were higher than those seeded on the other two dates across genotypes. We suppose that seeding date and N supply might be crucial determinants of flax lipid quality in temperate regions.