Genome Editing Approaches in Flax (<i>Linum usitatissimum</i> L.): From Tools to Trait Improvement.

Genome editing, particularly CRISPR/Cas-based systems, has emerged as a key tool for functional genomics and trait improvement in flax (Linum usitatissimum L.), an important fiber and oilseed crop. This review focuses specifically on flax as an emerging target species and distinguishes experimentally validated applications from approaches adapted from model plants. Recent progress includes the characterization of endogenous U6 promoters, which improved guide RNA expression and contributed to enhanced genome editing performance under optimized conditions. Reported studies demonstrate efficient targeted mutagenesis in flax; however, editing outcomes remain strongly dependent on genotype, construct design, and regeneration capacity, and stable homozygous edited lines are still limited. Target genes include pathways involved in lignin and cellulose biosynthesis, fatty acid metabolism, and stress responses, influencing fiber quality, oil composition, and stress adaptation. Despite current bottlenecks such as low homologous recombination efficiency and regeneration constraints, base editing, prime editing, and multiplex CRISPR systems provide promising avenues for precision breeding in flax.