Objectives
The objectives of this application were to:
- Determine the sample size of straw required for near infrared (NIR) analysis and survey the straw fibre concentration within the existing breeding program.
- Establish the optimum conditions for the expression and selection of fibre concentration in oilseed flax.
- Investigate the genetics and heritability of straw fibre concentration in oilseed flax.
- Investigate protocols for straw fibre breeding and determine the relationship among straw fibre concentration, seed yield, seed size, seed oil concentration and straw strength.
Project Description
The overall objective of this research was to determine the plant breeding protocols needed to increase and improve the straw fibre content in Canadian flax varieties. It had been expected that seed yield and straw fibre concentration would be negatively correlated as the flax plant would not have the resources to put into both fibre and seed. However, the results from these experiments indicate that this is not a negatively correlated relationship within oilseed flax. At worst it appears neutral and at best mildly correlated with seed yield and oil concentration. It should be possible to breed an oilseed flax variety that has a high straw fibre concentration along with good seed yield and good seed oil concentration. This can occur because straw fibre is laid down before seed and seed oil begin to be produced. Thus, they are not competing for resources.
The number of straw samples taken from a field plot of flax is somewhat dependent on the plot type and generation of the material/lines being evaluated. For the normal small yield plots used for evaluating more or less homozygous breeding lines one sample of plants of 5cm in diameter taken from one spot within the plot and using a minimum of 4 shuffled NIR scans of the sample is sufficient to determine the fibre content of that plot. These are replicated tests, so they also measure the effect of local environment on fibre content of an individual line. The fibre rankings of varieties for years were consistent so one year is all that is needed for the sorting out the relative straw fibre concentration a line. On the location side, several locations may be needed to determine the maximum level of straw fibre that can be expected among lines. While row spacing, seeding rate and seeding date all had an effect on straw fibre content there were generally no important interactions involving these factors. Nitrogen fertilizer had no effect on fibre.
If straw fibre is to be selected for in early, segregating generations it must be done on the basis of single rows replicated a minimum of three times. This would be difficult and expensive to do on all F3 – F5 lines grown each year as this would mean going from 10,000 single row plots a year to more than 30,000 such rows. The F3 ranking of lines with high levels of straw fibre was consistent with the F2 results. The F2 can be used to rank crosses (segregating populations) but the crosses will need to be replicated in the field and the number of scans of each collected bundle will need to be nine or more. Thus, the evaluation of F2 populations will allow the elimination of most crosses for developing high straw fibre containing varieties. Individual F3 plants from the high fibre crosses can then be grown in the phytotron during the winter to further select (identify) the F3 lines on the basis of stem sections. The best of these lines can then be evaluated in the field the following summer. Such a strategy will result in a great saving in space and resources and will allow for a high selection pressure for straw fibre.
Therefore, in general the field protocols at the Crop Development Centre do not need to be changed to accommodate the development of high straw fibre flax varieties with two important exceptions. The F2 crosses will need to be grown in replicated rows for fibre screening and the resulting F3 to F5 segregating generations will need to be replicated but only for the high straw fibre crosses. Also, since straw fibre does not seem to be correlated with oil content and seed yield these traits can be selected for in the segregating generations and the early yield testing stages of the high fibre crosses. The best selection scheme for straw fibre seed yield and seed oil content will be know once the thesis of Ph.D. student Natalie Coetzee is complete.
Grower Benefits
Flax straw is often burned because it is difficult to deal with. This results in air pollution and release of carbon into the atmosphere. Processing of this straw to extract the fibre would end up sequestering much of the carbon contained in the straw and producing a natural, biodegradable product. However, Canadian oilseed flax varieties have never been bred for high, stable straw fibre. The processing industry has found certain Canadian varieties have fibre levels that are reasonably high, but the levels are not consistent. This research has established the protocols needed to select and evaluate flax straw fibre concentration in a flax breeding program and has identified high fibre lines that have the potential of being developed into varieties for Canada. These results will, therefore, help in a small way to deal with Canada’s negative carbon balance and will also improve air quality. This will lead to the expansion of the Canadian straw fibre industry and help to establish flax as a true dual-purpose crop.
