Survival analysis of freezing stress in the North American native perennial flax, Linum lewisii

Abstract Abstract. The expansive range of Lewis flax (Linum lewisii), an herbaceous perennial, exposes the species to a diversity of climatic conditions. As interest in the domestication and adoption of perennial crop alternatives grows and interest in this species for natural area restoration continues, the assurance of a commercial plant variety’s ability to endure the full range of possible climatic extremes is paramount. This study examines the freezing tolerance of a geographically representative sampling of 44 Lewis flax accessions at winter temperature extremes experienced in the northern Great Plains of the USA. Survival analysis models were adapted to include temperature exposure, in replacement of ordinal time typically used in such models, to produce statistics evaluating reactions to extreme temperatures that Lewis flax would encounter in our field environments. Our results revealed Lewis flax is more freezing tolerant than previously reported, and revealed four accessions with significantly superior genetic freezing tolerance than the released ‘Maple Grove’ cultivar. Furthermore, regrowth analyses indicate variation among accessions not associated with survival, which could lead to improving regrowth rate and survival simultaneously. These findings and their methodology expand the understanding of Lewis flax adaptation for winter hardiness and offer an efficient, new model that can be used to evaluate freezing tolerance at ordinal temperatures without requiring extensive prior physiological knowledge for a species. This paper demonstrates that considerable diversity in tolerance to freezing temperatures exists among populations of Lewis flax (Linum lewisii ) throughout its range of western North America. Some of the freezing tolerance diversity is predicted by climate at the site of collection, but these relationships are complex. Differences in the rate of growth of seedlings exist independently within the range of freezing tolerance, suggesting that rapid seedling growth and freezing tolerance can be found together. This information is important to plant biologists interested in native plant restoration and novel oilseed domestication for agriculture.