Flax domesticationprocesses as inferred from genome-wide SNP data.

Area of Science:

• Agricultural Science
• Genetics
• Archaeobotany

Background:

• Flax (Linum usitatissimum L.) is a foundational crop from the Fertile Crescent, historically used for oil and fiber.
• While some aspects of flax domestication are known, the role of multiple domestication events remains unclear.
• Previous genetic studies have shed light on the wild progenitor and early uses but lack detail on complex domestication pathways.

Purpose of the Study:

• To investigate the complex domestication processes of flax, particularly those involving multiple domestication events.
• To infer the demographic history and genetic relationships among different flax domestication groups and their wild progenitor.
• To date key domestication events, including the spread of oilseed/fiber flax and the development of winter hardiness.

Main Methods:

• Genotyping-by-sequencing (GBS) was employed on 93 Linum samples, encompassing four cultivated groups (oilseed, fiber, winter, capsular dehiscence) and the wild progenitor (L. bienne).
• Single Nucleotide Polymorphism (SNP) calling identified 16,998 SNPs distributed across 15 flax chromosomes.
• Analyses included nucleotide diversity, demographic inference (population expansion/contraction, mixture events), phylogenetic analysis, and divergence dating.

Main Results:

• Pale flax (L. bienne) exhibited the highest nucleotide diversity, with all cultivated groups showing signs of population expansion post-bottleneck.
• Genetic signals of multiple mixture events were detected, particularly in oilseed flax.
• Phylogenetic analysis revealed two main subclades: one with Near Eastern origins (winter, oilseed, fiber flax) and another with European origins (oilseed, fiber flax).
• Divergence dating suggests oilseed and fiber flax spread to Europe 5800 years BP, and domestication for winter hardiness occurred in the Near East 5100 years BP.

Conclusions:

• Flax domestication involved complex processes including multiple mixture events and distinct geographic origins for different types.
• The study provides significant insights into the evolutionary history of oilseed, fiber, and winter-hardy flax varieties.
• Findings illuminate the timeline and geographic spread of key domestication traits in flax.