Assessment of biogeographic variation in traits of Lewis flax (Linum lewisii) for use in restoration and agriculture

Abstract

Lewis flax (Linum lewisii) is widely distributed across western North America and is currently used in native ecosystem restoration. There is also growing interest in de novo domestication of Lewis flax as a perennial oilseed crop. To better understand this species and facilitate both restoration and domestication, we used common gardens to assess bio-geographical variation in a variety of seed and growth traits from 37 flax accessions, consisting of 35 wild populations from the Intermountain West region, the pre-variety germplasm Maple Grove (L. lewisii) and the cultivar ‘Appar’ (L. perenne) and related this variation to collection site geography and climate. Results from linear mixed models suggest there is extensive phenotypic variation among populations of Lewis flax within the Intermountain West. Using a multivariate approach, we identify a key suite of traits that are related to latitude and climate and may facilitate adaptation, including flowering indeterminacy, seed mass, and stem number. These traits should be taken into account when considering the release of new germplasm for restoration efforts. We also find that Lewis flax seed contains desirably high amounts of alpha-linolenic acid and is otherwise mostly indistinguishable in fatty acid composition from oil-type varieties of domesticated flax (L. usitatissimum), making it a strong candidate for domestication. This study provides fundamental knowledge for future research into the ecology and evolution of Lewis flax, which will inform its use in both restoration and agriculture.

First steps toward developing Lewis flax (Linum lewisii Pursh) as an agronomic crop

“…Lewis flax seeds are smaller than domesticated annual flax, with an observed range in 1000 seed mass from 1.5 to 3.4 g, compared to 5.77 g for annual flax (Pradhan et al, 2010; Innes et al, 2022). Planting depth recommendations for growing Lewis flax in an agronomic context suggest planting at a depth of 0.6–1.3 cm (¼–½ inch; USDA-Natural Resources Conservation Service, 2004).…”

“…Observationally, a large proportion of the seed yield was lost due to flax boll shattering that left the seed on the soil surface before combining occurred. Breeding efforts to improve Lewis flax as an agronomic crop plant must focus on driving variation toward more determinant flowering and reduction of boll shattering to increase harvestable yield (Innes et al, 2022). Another factor possibly involved in low yield was lack of fertility.…”

“…Wet weather also likely contributed to rust infection, which was observed affecting many plants at Absaraka. We assume that this infection was flax rust ( Melampsora lini ), a pathogen known to infect domesticated annual flax, or a closely related rust species that infects Lewis flax (Innes et al, 2022).…”

“…In addition to potential ecosystem and agricultural system resiliency benefits, Lewis flax seed is rich in omega-3 fatty acids, which are indistinguishable from those produced by cultivated annual flax ( Linum usitatissimum ) varieties (Innes et al, 2022). The human health benefits of omega-3s are well-documented; therefore, Lewis flax seeds could potentially be marketed similarly to annual flax (Singh et al, 2011; Tork et al, 2019).…”

Chromosome-scale Genome Assembly of Lewis Flax (Linum lewisiiPursh.)

“…Lewis flax ( Linum lewisii Pursh, 2n = 2x = 18), a short-lived perennial, is one of just two blue-flowered flax species native to North America (the other being the annual L. pratense Small). It has a broad distribution mostly spanning the Rocky Mountains and shows substantial trait variation (Innes et al, 2022; Meyer and Kitchen, 1994; Mosquin, 1971). Other members of the blue-flowered clade have natural ranges across Europe and Asia, including domesticated flax ( Linum usitatissimum ), the source of linseed and linen, among other products.…”