Project Description
The objectives of this project were to deliver novel, non-GMO, pre-breeding variants of an elite Canadian linseed variety (CDC Bethune), in which straw strength had been moderately reduced. This was to be accomplished through forward phenotypic screening of an existing EMS-mutagenized population, which has already been well-characterized. Individuals from this population have also been subjected to resequencing for reverse genetics screening (i.e identification of mutations in genes of interest by DNA analysis of targeted genes).
The project did not achieve its primary objective, because no CDC Bethune lines were identified that showed reproducible, moderate reductions in straw strength in greenhouse-grown materials. Assay methods included an Instron micro-tensile strength tester. Ultimately, even for greenhouse-grown materials from the same line, the variability in stem properties was too large to identify reproducibly useful phenotypic variants. This was due to the small sample size available for each line when plants were greenhouse grown, and because the mutagenized plants were still segregating for a variety of mutations. If the forward-mutant screen approach were to be attempted in the future, it is recommended that genotypes be grown in small field-grown plots and stem phenotypes be averaged over at least 30 plants of each genotype.
Alternative approaches to identifying pre-breeding material were undertaken, including reverse genetics screening of the same mutant population use for forward screening. Target genes belonging to gene families with expected roles in cell wall development were selected from a list of indexed mutations previously identified using exome capture sequencing. Since the last update, we attempted to recover lines with mutations in the following genes. However, re-sequencing of all four lines failed to show a reproducible mutation at the positions previously identified. Therefore, this strategy was not pursued further.
Previously, our lab has identified a mutant of CDC Bethune (rdf; reduced fiber) that reproducibly lacks nearly all bast fibers. Field testing of this mutant by Helen Booker showed it to have too severe of a reduction in stem strength to be useable, as plants had a prostrate growth habit. Other breeders (Paul Dribnenki, Jodi Souter) have nevertheless encouraged further investigation of this mutant as a potential straw management solution, and we thus provided seed of rdf to Jodi Souter for additional backcrossing and field testing. Seed of backcrossed and selfed rdf plants were grown in the field in 2022 and stem properties are currently being examined.
