Flax (Linum usitatissimum L.) genomics and breeding

Abstract

Flax (Linum usitatissimum L.) is a self-pollinating crop grown for its stem fiber and seed oil. Owing to long-term domestication, cultivated flax has diversified into two main morphotypes, namely fiber and oil or linseed types. In the last decade, significant progress has been achieved in flax genomics, such as the development of genetic and physical maps, chromosome-scale reference genome sequences, a large number of molecular markers (SSRs, SNPs) and quantitative trait loci (QTL) associated with traits of importance. Genome-wide markers and QTL can be effectively used for the evaluation of flax germplasm. Rust, Fusarium wilt, powdery mildew, and pasmo are four major diseases of concern in flax breeding. Biparental hybridization breeding with pedigree selection and off-season operations remains the predominant method of improvement in Canadian linseed breeding programs, requiring about ten years to reach registration of a cultivar. However, use of the doubled haploid (DH) method may shorten this breeding cycle by approximately two years or three generations and simultaneously be advantageous for application of genomic selection (GS). The mapping of QTL for target traits may accelerate application of molecular breeding in flax improvement programs. Genome-wide QTL have shown potential in GS for the prediction of complex quantitative traits. With more QTL identified, it is possible to pyramid all superior alleles of target traits by multiparental crossing combining DH and GS to develop superior cultivars.