Objectives
The objective of this study was to evaluate the flax germplasm collections to determine if sufficient variability existed that could be used in a breeding program to either increase the level of SDG in current cultivars or to develop new cultivars with high levels of SDG specifically for the nutraceutical and functional food markets.
Project Description
The levels of the lignan secoisolariciresinol diglucoside (SDG) in flax seed is of particular interest because of the biological activity and health benefits attributed to this compound either as a component of flax seed in the diet or as an isolated and purified compound with potential markets as a nutraceutical, health food or as a pharmaceutical. In a previous study of the levels of SDG found in the seed of Canadian commercial cultivars, significant cultivar variability was observed. The bulk of the flax germplasm collection of Plant Gene Resources of Canada (PGRC) was historically subdivided into 6 general categories (spring, winter, forage, fibre, Indian, and Mediterranean). This collection also contains a small number of related Linum species and a number of L. usitatissimum L. accessions that did not fit the 6 general categories. Three seeds drawn at random for each accession were analyzed for SDG using a modified method that permitted analysis of individual seeds. A random selection of between 80 and 200 accessions from each group were selected for analysis. The mean SDG level for the 949 accessions examined was 11.34 ±3.85 mg/g of seed. A total of 16 accessions contained SDDG levels that ere greater than 2 SD from the mean and 15 of the 16 came from the Indian, Mediterranea and spring subgroups. Further agronomic and biochemical evaluation of these accessions will determine if they have potential to be developed directly into new cultivars. If these accessions do not have the desired agronomic characteristics, then the high lignan trait can still be incorporated into desirable cultivars by the application of classical breeding techniques.
The highest mean recorded was 27.49 mg SDG/g of seed for an accession of Mediterranean flax and the highest single seed value found was 30.49 mg SDG/g. Although the oil content of the high lignan accessions is not known at this point in time, one might expect an oil content of approximately 30% which would give a meal SDG content of approximately 40 mg/g (4%). If this could be achieved in a commercial cultivar, it would represent more than double the SDG content of commercial flax meal which is typically in the 1.2-1.7% range. This has significant implications for the flax industry, both in terms of the processing of flax meal for the recovery of lignans, and also for the possible development of a flax cultivar specifically designed for direct consumption as a functional food. If the pharmaceutical, nutraceutical and functional food market for flax lignans develops as expected, then it will be desirable to increase the average lignan content of commercial cultivars and one would expect this to be reflected in the farm gate price of flax seed and also in greater price stability. The development of a nutraceutical flax cultivar with elevated lignan levels, possibly at the expense of oil and gum content would represent a new market opportunity for the industry.
Several of the Linum species contain SDG levels that were greater than twice the highest level found in L. usitatissimum L. seed. This offers an alternative source of genetic material for the development of high lignan cultivars. There are also several species that contain significant unidentified peaks which may represent compounds with potential value either as precursors of the synthesis of biologically active molecules or because they have useful activity themselves.
The direct impact of this research is still some way off, however it does indicate that there is potential to proceed with a program to develop high lignan cultivars and to increase the lignan content of existing flax cultivars through a process of conventional plant breeding.
